JP4838590B2 - Ophthalmic imaging apparatus and artifact detection method thereof - Google Patents

Description

  The present invention relates to an ophthalmologic imaging apparatus such as a fundus camera having an imaging device capable of capturing an eye image used in an ophthalmic clinic or the like, and an artifact detection method thereof.

  In recent years, many apparatuses using an image sensor have been developed, and electronic filing, remote diagnosis, diagnosis support by a computer, and the like are performed in an ophthalmologic photographing apparatus. In this case, an ophthalmic imaging apparatus has been developed that obtains an eye image as an electronic image using a CCD sensor or a digital single lens reflex camera instead of a conventional silver salt film camera.

  In such an ophthalmic imaging device, dust may enter the inside of the device while it is being used, and may adhere to the vicinity of the lens, mirror, or imaging device. There is a need to do.

  In particular, when a subject eye image is taken with dust adhering to the vicinity of the image sensor, the part corresponding to the dust position on the fundus image becomes dark and looks like an aneurysm seen in retinopathy, A normal eye may be misdiagnosed as having findings. Further, if dust adheres to the lens or mirror, the reflected light of the dust enters the image sensor as stray light, and flare occurs on the image, making it difficult to accurately diagnose the affected area.

  Patent Document 1 proposes a correction method for ghost light that appears due to reflected light caused by such dirt on the objective lens. However, when there is an artifact other than ghost light, such as dust in the vicinity of the image sensor, the operator or service person confirms the presence or absence of the artifact by test pattern photography or the like. Then, it is necessary to identify the position of the dust from the shape and color of the artifact and to clean the place. This confirmation and cleaning work takes time, and there is a problem that only an operator having specialized knowledge of the apparatus can perform it.

JP 2004-16486 A

  An object of the present invention is to solve the above-mentioned problems, detect artifacts on an image with a simple operation, estimate the cause of each artifact, and notify the user of the fact, and an artifact detection method therefor Is to provide.

In order to achieve the above object, an ophthalmic imaging apparatus according to the present invention includes:
A sensor that captures an image of the subject via an imaging optical system;
A zoom lens disposed on an optical path of the imaging optical system;
If the variation amount of the artifact detected from each of the test pattern images captured by the sensor by moving the zoom lens to a plurality of positions is smaller than a predetermined value, it is classified as dust on the sensor surface, and from the predetermined value A classification means for classifying it as other if larger,
It is characterized by having.

In order to achieve the above object, an ophthalmic imaging apparatus according to the present invention includes:
An illumination optical system that irradiates a subject with light emitted from a light source through an objective lens;
An imaging optical system for imaging the return light from the subject through the objective lens and the imaging aperture;
A sensor that captures an image of the subject via an imaging optical system;
A diffuser plate detachably disposed between the imaging diaphragm and the sensor on the optical path of the imaging optical system;
And an artifact detection means for detecting an artifact from a test pattern image photographed by the sensor in each of a state where the diffusion plate is inserted and a state where the diffusion plate is not inserted .

  According to the ophthalmologic imaging apparatus and the artifact detection method thereof according to the present invention, it is possible to detect an artifact on an image with a simple operation and to estimate the cause of each artifact.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram of the fundus camera of the first embodiment. The objective lens 1 is disposed in front of the eye E, and a perforated mirror 2, a photographing aperture 3 disposed in the hole of the perforated mirror 2, and a movable focus lens 4a are included on the rear optical path. An imaging unit 6 such as a photographing lens 4, a movable mirror 5, and a CCD sensor is disposed. A half mirror 7 is arranged in the reflection direction of the movable mirror 5, a relay lens 8 is arranged in the reflection direction, and a television camera 9 having sensitivity in the infrared wavelength region is arranged. The output of the television camera 9 is connected to the television monitor 10. ing.

  In the transmission direction of the half mirror 7, a fixation lamp 11 configured by an LED array arranged in a dot matrix is disposed in a conjugate manner with the fundus oculi Er so as to present a fixation target to the eye E to be examined.

  In the incident direction of the illumination light to the perforated mirror 2, from the observation light source 12 side made of a halogen lamp or the like, a condenser lens 13, a visible light cut filter 14, a strobe light source 15, a diaphragm 16 having a ring-shaped opening, and a relay lens 17. Are arranged.

The output of the imaging means 6 is connected to the image control unit 22 via the A / D conversion unit 21. Connected to the image control unit 22 is a control means 23, an image display monitor 24, and an image recording means 25 for writing to or reading from a non-volatile recording medium such as a DVD-RAM. Further, the control unit 23 is connected with a fixation lamp 11, a photographing switch 26, an information input unit 27, a strobe light emission circuit 28 for emitting a strobe light source, and a focus lens control unit 29 for controlling the position of the focus lens 4a.

  In this way, the fundus observation imaging optical system is configured by the objective lens 1, the imaging aperture 3, and the imaging lens 4, and the fundus imaging optical system that images the fundus Er of the eye E together with the imaging unit 6 is configured. The movable mirror 5, the half mirror 7, the relay lens 8, the television camera 9, and the television monitor 10 constitute an observation optical system that presents a fundus image to the photographer, and is illuminated from the observation light source 12 by the optical path of the perforated mirror 2. An optical system is configured.

  At the time of operation, the photographer confirms that the device is in the normal photographing mode, and then the patient's ID number, name, birth date, sex, etc., patient information and file format for outputting the photographed image, etc. Is input from the information input means 27 to the control means 23. Next, the photographer places the eye E in front of the objective lens 1 and performs alignment for fundus photography.

  At this time, the fixation target 11 is turned on, and the fixation target is presented at an arbitrary position with respect to the eye E by an instruction from the control means 23 by controlling transmission / non-transmission of dots at two-dimensional arbitrary positions. And the position of the eye E is fixed.

  When the observation light source 12 is turned on, visible light is emitted, and the light is collected by the condenser lens 13. Further, the observation light converted into infrared light by the visible light cut filter 14 passes through the strobe light source 15, the diaphragm 16 and the relay lens 17, and is reflected to the left by the mirror portion of the perforated mirror 2. The observation light passes through the objective lens 1, projects a ring-shaped opening near the pupil of the eye E, and illuminates the fundus Er through the pupil Ep.

  Then, the image of the fundus Er illuminated by the observation light passes again through the objective lens 1, the photographing aperture 3, and the photographing lens 4 and is reflected upward by the movable mirror 5, and further reflected leftward by the half mirror 7, and the relay lens. 8 reaches the TV camera 9. The television camera 9 having sensitivity to infrared light converts the received fundus image into a video signal and outputs the video signal to the television monitor 10. While viewing the fundus image presented on the television monitor 10, the photographer performs precise alignment, focusing, and confirmation of the photographing range between the eye E and the fundus camera.

  After confirming that the shooting range, position, and focus are good, the photographer operates the shooting switch 26 to take a still image. The control means 23 that has detected the input of the photographing switch 26 jumps up the movable mirror 5 and retracts it from the optical path. At the same time, it outputs a photographing start signal to the image control unit 22 and then the strobe light source 15 from the image control unit 22. Wait for the light emission timing signal for.

When the control unit 23 receives the light emission timing signal of the strobe light source 15 from the image control unit 22, it sends a light emission signal to the strobe light emission circuit 28 without delay, and the strobe light source 15 emits a visible light flash. The luminous flux emitted from the strobe light source 15 passes through the ring-shaped aperture of the diaphragm 16 like the observation light, passes through the relay lens 17, and is reflected to the left by the mirror part around the perforated mirror 2. The fundus Er is illuminated from the pupil Ep of the eye E. The fundus image illuminated in this way passes through the objective lens 1, the photographing aperture 3 in the hole of the perforated mirror 2, and the photographing lens 4 again to form an image on the imaging surface of the imaging means 6. The imaging means 6 is a video. The signal is output to the A / D converter 21.

  The image control unit 22 synchronizes the video signal for one frame output from the imaging means 6 with the strobe light emission, converts it into digital data by the A / D conversion unit 21, and then captures it into the frame memory. Thereafter, as shown in the flowchart of FIG. 2, image processing is performed, and image supplementary information such as patient information, examination information, and image processing information is written. Then, as shown in FIG. 3, the fundus image taken on the image display monitor 24 is displayed together with accompanying information such as a patient ID. Thereafter, it can be transmitted to the image storage destination according to an instruction from the information input means 27.

  It is desirable to perform the dust check operation periodically at the start-up of the apparatus or once every week or every 100 shots. In addition, when the photographed image is browsed and an artifact suspected of being caused by dust is noticed, an image free of artifacts can always be obtained by appropriately performing the dust check operation.

  FIG. 4 shows a flowchart of the dust check operation. First, when a dust check operation start command is input from the mode button information input means 27 (not shown), the control means 23 enters the dust check mode. The photographer uses a model eye having a test pattern, for example, and aligns the model eye at the same position as the eye E to be examined. The model eye has optical characteristics imitating the human eye, but the captured area corresponding to the fundus has a uniform reflectance so that artifacts due to dust and the like on the captured image can be easily recognized.

  The photographer presses the photographing switch 26 after confirming the position of the model eye and the fundus camera and confirming the photographing range while viewing the fundus image of the model eye presented on the television monitor 10. The control means 23 that has detected the input of the shooting switch 26 uses the focus lens control means 29 to set the focus position to the standard position (position of diopter correction 0). Therefore, the test pattern portion is photographed by the model eye and converted into digital data by the same processing as the photographing of the normal eye E, and is taken into the frame memory.

  FIG. 5A shows an example of a captured dust check image 1. If there is dust or the like, dust is depicted as an artifact on the test pattern surface having uniform brightness. Can be done.

  After the dust check image 1 is normally recorded, the control unit 23 operates to photograph the same model eye test pattern at different focus positions. Specifically, in response to a command from the control means 23, the focus lens control means 29 is used to move the photographic lens 4 to a position different from the standard position, for example, a diopter + 10D (diopter) position, and again a model eye test pattern. Take a photo of As described above, the dust check image 2 shown in FIG. 5B taken with the focus shifted is recorded in the frame memory together with the dust check image 1.

  By comparing the images taken in different focus states, that is, the dust check images 1 and 2, it is possible to know the influence of the movement of the focus on the artifact. That is, it is possible to determine whether the cause of each artifact is on the imaging surface at the focus position or on the lens or mirror surface.

  In the image processing, first, the image control unit 22 binarizes the dust check image 1 at a predetermined level to obtain a binarized dust check image 1 as shown in FIG. Next, a labeling process is performed, and a black pixel (a pixel having a pixel value of 1) that is continuous is defined as one block, and the barycentric position (xi, yi) and area Ai (number of pixels) of each block are obtained.

  Next, the binarization process is similarly performed on the dust check image 2 to obtain a binarized check image 2 as shown in FIG. 6B, and each block extracted by the same process is obtained. , The barycentric position (x′j, y′j) and the area A′j are obtained.

  The lump extracted from the dust check image has an area within a predetermined range, for example, a lump that is considered to be the size of dust, such as 10 pixels or more and 100 pixels or less. Matches within a predetermined range. With this criterion, artifacts that appear regardless of the focus position can be identified as dust on the imaging surface, and control is performed on the information about the position and area of the center of gravity of each of the identified lump on the imaging surface. Transmit to means 23.

  Here, the image processing method of artifact extraction for the dust check images 1 and 2 and the method of determining the approximation of the artifact are not limited to the above-described methods, and other methods can obtain the same effect. Not too long. For example, when extracting an artifact, a lump can be extracted with higher accuracy if shading correction is performed as preprocessing. As for the approximation of the lump, the dust on the imaging surface can be more reliably determined by extracting and comparing not only the position and area but also the features such as moment, curvature, and shape. Further, the image can be analyzed as it is as a multi-valued image without being binarized, and the accuracy of judgment such as dust detection can be improved.

  The control means 23 that has received the information on the dust on the imaging surface displays the information on the dust and a message prompting cleaning on the monitor 24. For example, as shown in FIG. 7, information such as the position of dust and a question as to whether or not to perform a cleaning operation are displayed together with the dust check image 1. Thereby, the operator can know whether there is dust, the position and degree of the dust, or the like based on the information displayed on the monitor 24.

  If the operator determines that cleaning is necessary, an instruction to enter the cleaning mode is given from the information input means 27, and the apparatus cover is removed to remove dust. If it is determined that there is no need for cleaning, when an instruction to that effect is given from the information input means 27, the apparatus shifts to the normal shooting mode and enters a state where normal shooting is possible.

  In addition to displaying dust on the imaging surface, the information on dust can be displayed together with other dust on the lens or mirror as shown in FIG. In that case, it is possible to specify a place to be cleaned whether dust that causes each artifact is on the imaging surface or in another optical system, so that the cleaning operation can be performed efficiently. Further, when cleaning is not performed, it is possible to know in advance what kind of artifact is in which place, so that it is not mistaken for an aneurysm or the like at the time of image interpretation.

  In this way, the operator can know whether there is any artifact in the captured image, the presence or absence of dust on the imaging surface, and the position of the image on the image with a simple operation, so that reliable diagnosis can be performed without being affected by the artifact. It can be carried out.

  Further, in addition to the above-described embodiment, image correction that removes artifacts due to dust may be performed. For example, the operator selects not to clean in the flowchart of FIG. Then, on the image shot in the normal shooting mode, image correction such as substituting the average value of surrounding pixel values for the position of the lump determined to be dust on the imaging surface by the above-described processing Process. As a result, an image suitable for diagnosis in which artifacts on the image due to dust are simply removed can be obtained.

  The dust on the imaging surface is less likely to change depending on the focus position at the time of shooting, the pattern of the subject, and the like, and thus dust removal processing by image processing is easy. However, for other dust on the lens or mirror, artifacts appearing depending on the focus position, the pattern of the subject, and the like are different, so that more advanced image correction processing is required. Therefore, the above-described processing is performed on dust on the imaging surface, and processing such as Patent Document 1 is performed on other dust. That is, these artifacts can be removed together by using an image obtained by photographing the correction pattern image under a plurality of conditions by combining the parameters of the photographing diopter, the focus position, and the photographing light amount during the dust check operation.

  FIG. 9 is a configuration diagram of a fundus camera according to the second embodiment. Although the configuration is almost the same as that of the first embodiment, a diffusing plate 31 is disposed between the perforated mirror 2 and the photographic lens 4 so that it can be inserted into and removed from the optical path by a driving means (not shown) according to an instruction from the control means 23 Has been. The diffusing plate 31 is disposed at a position non-conjugated with the fundus oculi, and even if there is some unevenness such as scratches or dust on the diffusing plate 31, it does not appear in the image, and the dust check operation is performed reliably. be able to.

  FIG. 10 is a flowchart of the dust check operation in the second embodiment. First, the photographer presses the photographing switch 26 after checking the position of the model eye and the fundus camera and confirming the photographing range while viewing the model eye test pattern presented on the television monitor 10. The control means 23 that has detected the input of the photographing switch 26 shoots a model eye test pattern by the same processing as in normal photographing, converts it into digital data as a dust check image 1, and then captures it into the frame memory.

  After the dust check image 1 is normally recorded, the control unit 23 operates to insert the diffusion plate 31 into the optical path and photograph the same test pattern. The captured dust check image 2 is recorded in the frame memory together with the dust check image 1. Thereafter, dust is detected by the same processing as in the first embodiment.

  In the second embodiment, by comparing the images captured by inserting / removing the diffusion plate 31, that is, the dust check images 1 and 2, it is possible to specify in more detail where the dust causing the artifact is. Can do. For example, since dust on the objective lens 1 is diffused by the diffusion plate 31, it appears greatly blurred on the dust check image 2. The position and brightness of the dust on the image pickup means 4 and the image pickup means 6 are not changed by the insertion of the diffusion plate 31, but the dust on the image pickup means 6 is a clearer image. Can be distinguished from dust.

  Further, the focus lens control means 29 of the first embodiment may be used together in order to reliably distinguish the dust of the objective lens 1 and the dust of the photographing lens 4. In other words, by combining the insertion and removal of the diffusion plate 31 and the focus position as parameters and capturing a plurality of dust check images, it is possible to classify dust more reliably.

1 is a configuration diagram of Example 1. FIG. FIG. 6 is a flowchart of normal fundus photographing operation according to the first embodiment. 3 is an explanatory diagram of a normal fundus image captured in Example 1. FIG. It is a flowchart figure of the dust check mode of Example 1. FIG. It is explanatory drawing of a dust check image. It is explanatory drawing of the binarized dust check image. It is explanatory drawing of dust information and a warning display. It is explanatory drawing of dust information and a warning display. FIG. 6 is a configuration diagram of Example 2. It is a flowchart figure of the dust check mode of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Perforated mirror 4 Shooting lens 6 Imaging means 9 Television camera 10 Television monitor 11 Fixation lamp 12 Observation light source 15 Strobe light source 22 Image control part 23 Control means 24 Image display monitor 25 Image recording means 26 Shooting switch 27 Information Input means 28 Strobe light emission circuit 29 Focus lens control means 31 Diffuser

Claims (6)

A sensor that captures an image of the subject via an imaging optical system;
A zoom lens disposed on an optical path of the imaging optical system;
If the variation amount of the artifact detected from each of the test pattern images captured by the sensor by moving the zoom lens to a plurality of positions is smaller than a predetermined value, it is classified as dust on the sensor surface, and from the predetermined value A classification means for classifying it as other if larger,
An ophthalmic imaging apparatus characterized by comprising: The ophthalmic imaging apparatus according to claim 1, wherein the subject is a model eye, and a test pattern is provided on the model eye. Ophthalmologic image pickup apparatus according to claim 1 or 2, characterized in that it has the artifact and display means for displaying the classification. An illumination optical system that irradiates a subject with light emitted from a light source through an objective lens;
An imaging optical system for imaging the return light from the subject through the objective lens and the imaging aperture;
A sensor that captures an image of the subject via an imaging optical system;
A diffuser plate detachably disposed between the imaging diaphragm and the sensor on the optical path of the imaging optical system;
An ophthalmic imaging apparatus, comprising: an artifact detection unit configured to detect an artifact from a test pattern image captured by the sensor in each of a state where the diffusion plate is inserted and a state where the diffusion plate is not inserted .   5. The ophthalmic imaging apparatus according to claim 1, further comprising an image correction unit configured to perform image correction for removing the artifact based on a result of the artifact detection unit. A first imaging step of obtaining a first test pattern image by imaging a test pattern using an eye imaging unit of an ophthalmic imaging apparatus;
A second imaging step of imaging the test pattern by changing the focus to obtain a second test pattern image;
If the variation amount of the artifact detected from each of the test pattern images is smaller than a predetermined value, it is classified as dust on the sensor surface, and if it is larger than the predetermined value, it is classified as other .
An artefact detection method for an ophthalmologic imaging apparatus comprising: