WO2018008613A1

WO2018008613A1 - Ophthalmic imaging device

Info

Publication number: WO2018008613A1
Application number: PCT/JP2017/024409
Authority: WO
Inventors: 藤生賢士朗
Original assignee: 株式会社ニデック
Priority date: 2016-07-04
Filing date: 2017-07-03
Publication date: 2018-01-11
Also published as: JPWO2018008613A1; JP6836212B2

Abstract

An SLO 1 has: an irradiation optical system 10 which irradiates a subject's eye with light from a light source 11 while a scanning part 16 is performing scanning with the light; and a light-receiving optical system 20 having light-receiving elements 25, 27, 29 that at least receive return light from the subject's eye. A control unit 70 of the SLO 1: acquires a photographed image of the subject's eye on the basis of signals from the light-receiving elements; causes a second image to be formed that has a smaller pixel count compared with the photographed image, or that requires a shorter time to form an image per frame compared with the photographed image; sets at least one condition concerning a photographed image on the basis of the second image; and captures a photographed image according to the set conditions.

Description

Ophthalmic imaging equipment

The present disclosure relates to an ophthalmologic imaging apparatus that images an eye to be examined.

Conventionally, an ophthalmologic photographing apparatus that adjusts various conditions such as photographing conditions using an image of an eye to be examined is known.

For example, Patent Document 1 discloses the following apparatus as a scanning laser ophthalmoscope which is a kind of ophthalmic imaging apparatus. That is, as a result of acquiring a plurality of fundus images while changing the diopter correction amount and comparing the image formation state of each fundus image, the diopter correction amount when obtaining a captured image is set to a suitable image formation state. An apparatus that adjusts to a value that yields is disclosed.

Further, for example, Patent Document 2 discloses the following apparatus as an optical coherence tomometer which is a kind of ophthalmic imaging apparatus. That is, a plurality of tomographic images are acquired while changing the optical path length difference between the measurement light and the reference light, and as a result of comparing the signal distributions in the depth direction in the tomographic images, the imaging range in the depth direction is obtained. An apparatus is disclosed in which the optical path length difference is adjusted to include the desired tissue.

JP 2009-291253 A JP 2012-213489 A

In the above adjustment method, when a certain condition is adjusted, it is necessary to acquire images of a plurality of eyes to be examined whose conditions are different from each other. Moreover, the process which detects the information regarding conditions is performed with respect to each of the image of several eyes to be examined. For this reason, it is easy to prolong the time required for adjusting the conditions.

The present disclosure has been made in view of the problems of the prior art, and an object of the present disclosure is to provide an ophthalmologic photographing apparatus in which the time required for adjusting the conditions is easily suppressed.

In order to solve the above technical problem, an ophthalmologic photographing apparatus according to the first aspect of the present disclosure includes an irradiation optical system that irradiates an eye to be examined while scanning light from a light source by a scanning unit, and a return from the eye to be examined. A light receiving optical system having a light receiving element that receives at least light; an image forming unit that obtains a photographed image of an eye to be inspected based on a signal from the light receiving element; and a pixel compared to the photographed image A second image having a smaller number or a shorter time required to form an image per frame than the captured image is formed on the image forming means, and at least one of the conditions relating to the captured image is set as the second image. Condition setting means for setting based on the above and shooting execution means for capturing the shot image according to the set condition.

れば According to the present disclosure, the time required for adjusting the conditions is likely to be suppressed.

It is the figure which showed the external appearance of SLO which concerns on an Example. It is the figure which showed the optical system of SLO which concerns on an Example. It is the figure which showed the control system of SLO which concerns on an Example. It is the flowchart which showed the operation | movement of SLO which concerns on an Example. It is the graph which showed the histogram of the differential value of the image brightness | luminance utilized by the autofocus in SLO of an Example.

First, the first embodiment of the present disclosure will be described. The ophthalmologic photographing apparatus according to the first embodiment irradiates the eye to be examined with light from the light source, and photographs an image of the eye to be examined as a result of receiving the return light. As such an apparatus, for example, an anterior ocular segment imaging apparatus, a fundus imaging apparatus, or an apparatus capable of imaging both the anterior ocular segment and the fundus oculi may be used.

Further, the ophthalmologic photographing apparatus may be, for example, a scanning type apparatus that scans light on the tissue of the eye to be examined, or a camera that receives return light from the eye to be examined by a light receiving element in which a plurality of pixels are arranged. The apparatus of a type | mold may be sufficient and the apparatus which has the characteristics of both may be sufficient. Examples of scanning devices include SLO (Scanning Laser Ophthalmoscope), OCT (Optical Coherence Tomography), and the like. Examples of the camera-type device include a fundus camera, an anterior eye camera, and an ophthalmic Shine-Pluke camera.

Hereinafter, the ophthalmologic photographing apparatus is referred to as this apparatus. The apparatus may include, for example, a photographing optical system (irradiation optical system and light receiving optical system), an image forming unit, a condition adjusting unit, a condition setting unit, and a photographing execution unit. At least a part of the image forming unit, the condition adjusting unit, the condition setting unit, and the photographing execution unit may be shared by one unit such as a computer built in the apparatus.

<Photographing optical system>
The photographing optical system is a main optical system of this apparatus that is used for acquiring an image of the eye to be examined. The photographing optical system includes at least an irradiation optical system and a light receiving optical system.

The irradiation optical system irradiates the eye to be examined with light from the light source. The irradiation optical system includes, for example, at least a part of a light source and an optical member (for example, a lens and a mirror) for guiding light from the light source to the eye to be examined. In the case of a scanning apparatus (SLO, OCT, etc.), the irradiation optical system may be provided with a scanning unit (optical scanner). The scanning unit is a unit for scanning the light emitted from the light source on the eye to be examined (more specifically, on the observation surface of the eye to be examined).

As the SLO, a two-dimensional scanning method in which spot-like light is scanned two-dimensionally (for example, raster scanning) on the observation surface, and a line scanning method in which line-shaped light is scanned in one direction on the observation surface. Is known. In any system, at least the scanning unit includes an optical scanner for scanning light in the sub-scanning direction. The present embodiment may be applied to either a two-dimensional scanning apparatus or a line scanning apparatus.

The light receiving optical system has at least a light receiving element. The light receiving optical system receives at least return light from the eye to be examined by the light receiving element. For example, in the case of OCT, the light receiving element does not receive the fundus reflected light (a kind of return light) of the measurement light itself, but the light in a state where the fundus reflected light and the reference light interfere with each other, The light receiving element may receive the light.

The present apparatus may be provided with another optical system separately from the photographing optical system or sharing at least a part of the photographing optical system. For example, a fixation optical system may be provided. In the case of OCT, a reference optical system for obtaining reference light may be provided.

<Image forming unit, shooting execution unit>
The image forming unit forms an image of the eye to be examined based on a signal from the light receiving element. The image of the eye to be examined formed by the image forming unit may be a front image or a cross-sectional image (or tomographic image). The image forming unit includes at least an image processing processor. The image processor may be a processor that controls the operation of the entire apparatus. The same applies to other configurations that handle images.

The photographed image is an image of the eye to be examined that is captured based on the photographing trigger signal. As a result of the capture, the captured image is stored in the memory. The captured image may be a raw image of the image of the eye to be examined, which is formed by the image forming unit, or may be an image obtained by processing, correcting, or both of the raw image. The capture is performed by the shooting execution unit.

<Condition adjustment section>
The condition adjusting unit adjusts at least one of the conditions set for obtaining the shooting conditions. The conditions adjusted by the condition adjustment unit may be hardware conditions (collectively referred to as imaging conditions) regarding the arrangement and operation of each part in the imaging optical system, or when forming a captured image from a light reception signal Conditions in software processing (referred to as image forming conditions in this embodiment) may also be used.

The photographing condition may be an adjustable condition for each part of the photographing optical system, and may be a condition that affects a photographing result (that is, an image). For example, the output from the light source, the amplification factor (gain) of the signal from the light receiving element, the diopter correction amount (focus), the arrangement of other optical members on the optical path, or the parameters relating to the operation of the optical members, etc. Can be mentioned. The condition adjusting unit can adjust at least a part of such shooting conditions.

Further, the image forming condition may be, for example, a condition in processing in which the image forming unit forms an image (mainly an image of the eye to be examined) based on a signal from the light receiving element. For example, the correction amount of brightness (a correction amount of at least one of brightness and contrast), the position correction amount of each part of the image, and the like can be mentioned as conditions. That is, the condition adjustment unit adjusts each condition by controlling a part of the photographing optical system or by adjusting the content of the image forming process in the image forming unit.

In the case of application to OCT, focus, optical path length difference between measurement light and reference light, polarization by a polarizer, etc. are exemplified as the above conditions.

<Condition setting section>
The condition setting unit causes the image forming unit to form a second image having a smaller number of pixels than the captured image or a shorter time required to form an image per frame than the captured image. The second image may be an image in which the subject's eye is a subject, such as a captured image, or may be an image in which the subject's eye is not a subject.

The conditions (conditions such as shooting conditions) set when shooting the second image are reflected in information (for example, luminance information, position information, etc.) included in the second image. Therefore, for example, the suitability of the condition can be determined by analyzing and evaluating the second image. The analysis / evaluation method may be image quality evaluation of the second image or histogram evaluation. In addition, an element correlated with at least one of various conditions may be evaluated.

The difference in the number of pixels between the shot image and the second image may reflect, for example, a difference in shooting range (shooting angle of view), a difference in pixel density with respect to the angle of view, or both. When this apparatus is a scanning-type apparatus, the condition setting unit may make the operation of the scanning unit different when acquiring a captured image and when acquiring a second image.

For example, the condition setting unit may change one of the scanning range and the scanning speed in the scanning unit in each case. In other words, the scanning range when acquiring the second image may be narrower than when acquiring the captured image, and the scanning speed when acquiring the second image is higher than when acquiring the captured image. You can be fast. As the scanning speed increases, the interval between the pixel extraction points on the eye to be examined increases, so the number of pixels of the image per frame is reduced.

In addition, the difference in time required to form an image per frame between the captured image and the second image reflects a difference in exposure time in addition to a difference in scanning range and scanning speed. Also good.

The condition setting unit sets at least one of the conditions to be set when capturing the captured image based on the second image. For example, a plurality of second images may be generated under different conditions by sequentially forming second images by the image forming unit while changing at least one condition by the condition adjusting unit. Then, a condition for obtaining a good captured image may be searched by analyzing and evaluating a plurality of second images. Note that each second image may be associated with information indicating a condition for generating the image.

The condition setting unit may set the searched conditions as “conditions to be set when capturing a captured image”. As a result, the shooting execution unit captures a shot image according to the conditions set by the condition setting unit when capturing the shot image.

Since the second image has a smaller number of pixels than the captured image, for example, the time required for the detection operation of “conditions to be set for capturing the captured image” is easily suppressed. More specifically, as in the present embodiment, compared to the case where “conditions to be set for capturing a captured image” are detected from a plurality of images formed with the same number of pixels as the captured image. In addition, the second image can be processed in a shorter time because the number of pixels is smaller.

In addition, when the second image is generated, the time required to acquire an image per frame is controlled by the scanning unit so that the second image is shorter than the captured image. When the number of pixels is smaller than that of the captured image, the time required for generating the second image among the time required for the detection operation is suitably suppressed.

At this time, the scanning unit may be controlled so that the scanning range when acquiring the second image is narrower than when acquiring the captured image. In this case, it is preferable that the narrowed scanning range is set near the center of the photographing optical axis. In the vicinity of the center of the photographing optical axis, vignetting is less likely to occur due to the pupil. Therefore, it is easy to satisfactorily detect “conditions to be set for capturing a photographed image” using the second image.

Further, the scanning unit may be controlled so that the scanning speed when acquiring the second image is faster than when acquiring the captured image. For example, during the condition detection operation by the condition setting unit, and before and after the condition, the image of the subject's eye is continuously captured, and the captured image of the subject's eye is displayed on the monitor in real time. The display range of the captured image can always be kept constant.

The condition setting unit temporarily outputs at least a part of a period from when an adjustment start trigger for a shooting condition or an image forming condition is issued until a “condition to be set when a captured image is captured” is detected. Then, the second image is formed.

Further, in the case of an apparatus in which the image of the eye to be examined is continuously captured before and after the operation of the condition setting unit and the captured image of the eye to be displayed is displayed on the monitor in real time, the second image is: The number of pixels may be smaller than that of the eye image displayed in real time before and after the operation of the condition setting unit.

<Example>
Next, an example in which the technique of the above embodiment is applied will be described. Here, an example applied to SLO is shown. For convenience, the SLO 1 according to the embodiment will be described as a configuration in which spot-like light is scanned two-dimensionally on the fundus. SLO1 may be an apparatus integrated with other ophthalmic apparatuses such as an optical coherence tomography (OCT) and a perimeter.

<Appearance configuration>
First, a schematic configuration of the SLO 1 will be described with reference to FIGS. As shown in FIG. 3, the SLO 1 mainly includes a photographing unit 4. The photographing unit 4 includes at least a main optical system (see FIG. 4) in the SLO1.

SLO1 may include an alignment mechanism. The alignment mechanism in SLO1 is used, for example, to arrange a position where a turning point of laser light is formed at an appropriate position with respect to the eye E. The alignment mechanism is a drive mechanism that adjusts the relative position between the eye to be examined and the imaging unit 4 (imaging optical system). The alignment mechanism may adjust the positional relationship between the eye to be examined and the imaging unit 4 (imaging optical system) in each of the X (left and right), Y (up and down), and Z (front and back) directions. In the specific example shown in FIG. 3, the base 5, the moving base 6, and the Z drive mechanism 7 are used as alignment mechanisms in the horizontal direction (XZ direction) and the vertical direction (Y direction). That is, the movable table 6 can move in the XZ direction on the base 5 with the photographing unit 4 placed thereon. The Y drive mechanism 7 is mounted on the movable table 6 and displaces the photographing unit 4 in the Z direction. As a result, the positional relationship between the eye to be examined and the imaging unit 4 (imaging optical system) in the XYZ directions is adjusted. The alignment mechanism may have an actuator that performs a predetermined operation based on a control signal in each of the X, Y, and Z directions, and may realize the above operation by driving control of the actuator.

<Optical configuration>
Next, the optical system provided in the SLO 1 will be described with reference to FIG. As shown in FIG. 4, the SLO 1 includes an irradiation optical system 10 and a light receiving optical system 20 (collectively referred to as “imaging optical system”). The SLO 1 takes a fundus image using these

optical systems

10 and 20.

The irradiation optical system 10 includes at least a scanning unit 16 and an objective optical system 17. As shown in FIG. 4, the irradiation optical system 10 further includes a laser beam emitting unit 11, a collimating lens 12, a perforated mirror 13, and a lens 14 (in this embodiment, a part of the diopter adjusting unit 40). ) And the lens 15.

The laser beam emitting unit 11 is a light source of the irradiation optical system 10. In the present embodiment, the laser light from the laser light emitting unit 11 is used as illumination light irradiated from the irradiation optical system 10 to the fundus Er. The laser beam emitting unit 11 may include, for example, a laser diode (LD) and a super luminescent diode (SLD). Although a description of a specific structure is omitted, the laser beam emitting unit 11 emits light in at least one wavelength region. In the present embodiment, it is assumed that light of a plurality of colors is emitted from the laser light emitting unit 11 simultaneously or selectively. For example, in this embodiment, a total of four colors of light, ie, three colors in the visible range of blue, green, and red and one color in the infrared range, are emitted from the laser beam emitting unit 11. The light of each color can be emitted simultaneously or alternately. Three colors in the visible range of blue, green, and red are used for color photography, for example.

Laser light is guided to the fundus Er through the path of the light beam shown in FIG. That is, the laser light from the laser light emitting unit 11 passes through the collimating lens 12, the opening formed in the perforated mirror 13, passes through the lens 14 and the lens 15, and then proceeds to the scanning unit 16. The laser light reflected by the scanning unit 16 passes through the objective optical system 17 and is then applied to the fundus Er of the eye E. As a result, the laser light is reflected and scattered by the fundus oculi Er, or excites a fluorescent substance existing in the fundus oculi and generates fluorescence from the fundus. These lights (that is, reflected / scattered light, fluorescence, etc.) are emitted from the pupil as return light.

In this embodiment, the lens 14 shown in FIG. 4 is a part of the diopter adjustment section 40 (the focus adjustment section in this embodiment). The diopter adjustment unit 40 is used to correct (reduce) the diopter error of the eye E. For example, the lens 14 can be moved in the optical axis direction of the irradiation optical system 10 by the drive mechanism 14a. Depending on the position of the lens 14, the diopter of the irradiation optical system 10 and the light receiving optical system 20 changes. For this reason, by adjusting the position of the lens 14, the diopter error of the eye E to be examined is reduced. As a result, the condensing position of the laser light is applied to the observation site (for example, the retina surface) of the fundus Er. It becomes possible to set. Note that the diopter adjustment unit 40 may be an optical system different from that shown in FIG. 4, such as a Badal optical system.

The scanning unit 16 (also referred to as “optical scanner”) is a unit for scanning the fundus with laser light emitted from a light source (laser light emitting unit 11). In this embodiment, the scanning unit 16 includes two optical scanners having different scanning directions of laser light. That is, an optical scanner 16a for main scanning (for example, scanning in the X direction) and an optical scanner 16b for sub-scanning (for example, scanning in the Y direction) are included. The scanning period, scanning speed, etc. by each of the

optical scanners

16a, 16b may be changeable.

In the following description, it is assumed that the optical scanner 16a for main scanning is a resonant scanner and the optical scanner 16b for sub scanning is a galvanometer mirror. In the present embodiment, the resonant scanner, which is the optical scanner 16a for main scanning, is designed to vibrate the mirror section with a predetermined constant period and a constant scanning range (swing angle). On the other hand, the scanning speed and scanning range of the optical scanner 16b for sub-scanning are variable. However, other optical scanners may be applied to each of the

optical scanners

16a and 16b. For example, for each of the

optical scanners

16a and 16b, in addition to other reflecting mirrors (galvano mirror, polygon mirror, resonant scanner, MEMS, etc.), an acousto-optic device (AOM) that changes the traveling (deflection) direction of light, etc. May be applied.

When a line scan type apparatus is applied to SLO1, the scanning unit 16 may be replaced with an optical scanner that scans line-shaped laser light in a direction intersecting the line. This optical scanner is a sub-scanning optical scanner, and may be, for example, a galvanometer mirror or an acoustooptic device.

The objective optical system 17 is an SLO1 objective optical system. The objective optical system 17 is used to guide the laser light scanned by the scanning unit 16 to the fundus oculi Er. For this purpose, the objective optical system 17 forms a turning point P around which the laser light passed through the scanning unit 16 is turned. The turning point P is formed on the optical axis L1 of the irradiation optical system 10 and at a position optically cooperating with the scanning unit 16 with respect to the objective optical system 17. In the present disclosure, “conjugate” is not necessarily limited to a complete conjugate relationship, and includes “substantially conjugate”. In other words, the case where the fundus image is arranged so as to deviate from the complete conjugate position within the range allowed in relation to the purpose of use of the fundus image (for example, observation, analysis, etc.) is also included in “conjugate” in the present disclosure. However, the objective optical system of SLO1 is not limited to a lens system, and may be a mirror system, a combination of a lens system and a mirror system, or other optical systems. There may be.

The laser light that has passed through the scanning unit 16 passes through the objective optical system 17 and is irradiated to the fundus Er through the turning point P. For this reason, the laser light that has passed through the objective optical system 17 is turned around the turning point P as the scanning unit 16 operates. As a result, in this embodiment, laser light is scanned two-dimensionally on the fundus oculi Er. The laser light applied to the fundus Er is reflected at a condensing position (for example, the retina surface). Further, the laser light is scattered by the tissues before and after the condensing position. The reflected light and scattered light are each emitted from the pupil as parallel light.

Next, the light receiving optical system 20 will be described. The light receiving optical system 20 has one or a plurality of light receiving elements. For example, as shown in FIG. 4, you may have several light receiving

element

25,27,29. In this case, light from the fundus Er due to the laser light irradiated by the irradiation optical system 10 is received by the

light receiving elements

25, 27, and 29.

As shown in FIG. 4, in the light receiving optical system 20 in this embodiment, each member arranged from the objective optical system 17 to the perforated mirror 13 may be shared with the irradiation optical system 10. In this case, the light from the fundus is guided back to the perforated mirror 13 along the optical path of the irradiation optical system 10. The perforated mirror 13 receives light from the fundus Er while removing at least a part of noise light reflected by the cornea of the eye to be examined and an optical system (for example, a lens surface of an objective optical system) inside the apparatus. The light is guided to an independent optical path of the optical system 20.

The optical path branching member that branches the irradiation optical system 10 and the light receiving optical system 20 is not limited to the perforated mirror 13, and other beam splitters may be used.

The light receiving optical system 20 of the present embodiment has a lens 21, a pinhole plate 23, and a light separation unit (light separation unit) 30 in the reflected light path of the perforated mirror 13. In addition,

lenses

24, 26, and 28 are provided between the light separation unit 30 and the

light receiving elements

25, 27, and 29.

The pinhole plate 23 is disposed on the fundus conjugate plane and functions as a confocal stop in the SLO1. That is, when the diopter is appropriately corrected by the diopter adjustment unit 40, the light from the fundus Er that has passed through the lens 21 is focused at the opening of the pinhole plate 23. The pinhole plate 23 removes light from a position other than the condensing point (or focal plane) of the fundus Er, and the remainder (light from the condensing point) is mainly guided to the

light receiving elements

25, 27, and 29. .

The light separation unit 30 separates light from the fundus Er. In the present embodiment, the light from the fundus Er is light-selectively separated by the light separation unit 30. The light separation unit 30 may also serve as a light branching unit that branches the optical path of the light receiving optical system 20. For example, as illustrated in FIG. 4, the light separation unit 30 may include two dichroic mirrors (dichroic filters) 31 and 32 having different light separation characteristics (wavelength separation characteristics). The optical path of the light receiving optical system 20 is branched into three by the two

dichroic mirrors

31 and 32. Further, one of the

light receiving elements

25, 27, and 29 is disposed at the tip of each branch optical path.

For example, the light separation unit 30 separates the wavelength of light from the fundus Er and causes the three

light receiving elements

25, 27, and 29 to receive light in different wavelength ranges. For example, the

light receiving elements

25, 27, and 29 may receive light of three colors of blue, green, and red one by one. In this case, a color image can be obtained from the light reception results of the light receiving elements 25, the

collars

27 and 29.

In addition, the light separation unit 30 causes infrared light used in infrared imaging to be received by at least one of the

light receiving elements

25, 27, and 29. In this case, for example, fluorescence used in fluorescence imaging and infrared light used in infrared imaging may be received by different light receiving elements. In the present embodiment, fundus reflection light by infrared light is received by the light receiving element 25.

<Control system configuration>
Next, the control system of SLO1 will be described with reference to FIG. In SLO1, each part is controlled by the control unit 70. The control unit 70 is a processing device (processor) having an electronic circuit that performs control processing of each unit of the SLO1 and arithmetic processing. The control unit 70 is realized by a CPU (Central Processing Unit), a memory, and the like. The control unit 70 is electrically connected to the storage unit 71 via a bus or the like. The control unit 70 is also electrically connected to the laser beam emitting unit 11, the

light receiving elements

25, 27, and 29, the driving unit 14 a, the scanning unit 16, the input interface 75, and the monitor 80.

The storage unit 71 stores various control programs and fixed data. The storage unit 71 may store temporary data or the like. The image obtained by SLO1 may be stored in the storage unit 71. However, the present invention is not necessarily limited to this, and the image obtained in SLO1 may be stored in an external storage device (for example, a storage device connected to the control unit 70 via LAN and WAN).

In this embodiment, the control unit 70 also serves as an image processing unit (image forming unit). As the image processing unit, the control unit 70 forms a fundus image based on light reception signals output from the

light receiving elements

25, 27, and 29, for example. More specifically, the control unit 70 forms a fundus image in synchronization with the optical scanning performed by the scanning unit 16. For example, each time the sub-scanning optical scanner 16b reciprocates n times (n is an integer of 1 or more), the control unit 70 displays the fundus image of at least one frame (in other words, one sheet) (the light receiving element). Every time). In the following description, for the sake of convenience, one frame of the fundus image is formed for each round trip of the sub-scanning optical scanner 16b unless otherwise specified. In this embodiment, since the three

light receiving elements

25, 27, and 29 are provided, the control unit 70 uses a maximum of three types of images based on signals from the respective

light receiving elements

25, 27, and 29 for sub-scanning. Is generated every time the optical scanner 16b reciprocates once.

The control unit 70 may cause the monitor 80 to display a plurality of frames of fundus images sequentially formed based on the operation of the apparatus as described above as an observation image in time series. The observation image is a moving image including a fundus image acquired in real time. Further, the control unit 70 captures (captures) a part of a plurality of fundus images that are sequentially formed as a captured image (capture image). At that time, the captured image is stored in a storage medium. The storage medium for storing the captured image may be a non-volatile storage medium (for example, a hard disk, a flash memory, etc.). In this embodiment, for example, a fundus image formed at a predetermined timing (or period) is captured after outputting a trigger signal (for example, a release operation signal).

The control unit 70 can form fundus images with different numbers of pixels. For example, a fundus image can be obtained with four types of pixels of 4096 × 4096, 2048 × 2048, 1024 × 1024, 512 × 512 (both “number of pixels in the main scanning direction” × “number of pixels in the sub scanning direction”). It may be formable. For example, the number of pixels of the fundus image may be switched by changing the swing angle of the

optical scanners

16a and 16b according to the number of pixels. However, in this embodiment, the fundus image is obtained with any number of pixels. Also, the swing angle of each of the

optical scanners

16a and 16b is assumed to be constant.

In this embodiment, the scanning speed of the sub-scanning optical scanner 16b can be adjusted according to the number of pixels. In other words, the smaller the number of pixels of the acquired fundus image, the faster the sub-scanning optical scanner 16b is operated.

In this embodiment, for the main scanning optical scanner 16a (resonant scanner), the cycle of the reciprocating operation and the scanning range (swing angle) are substantially constant, and it is difficult to control the scanning speed and the scanning range. For this reason, the number of pixels in the main scanning direction may be switched by adjusting the pixel sampling period. Sampling of the signal from the light receiving element is performed in synchronization with a clock, for example. When the clock cycle is variable, the number of pixels in the main scanning direction may be switched by switching the sampling cycle itself of the signal from the light receiving element. On the other hand, when the clock period is constant and the sampling period of the signal from the light receiving element is constant, the extraction interval (resampling interval) of the signal used for pixel formation is switched from the once sampled signal. Thus, the number of pixels in the main scanning direction may be switched.

In this embodiment, a signal (for example, a square wave) synchronized with the period of each forward scan is output from the driver of the optical scanner 16a (resonant scanner) for main scanning. The generation timing of this signal or the timing when a predetermined time has elapsed from the generation timing is used as the acquisition timing of the first pixel in the pixel column (one of the first pixel column and the second pixel column) (in other words, Horizontal synchronization is obtained). Further, for example, the timing at which a half cycle of reciprocating scanning has elapsed from this timing is further used as the acquisition timing of the first pixel in the remaining one of the first pixel column and the second pixel column. As a result, the first pixel column is distinguished from the second pixel column, and a fundus image is constructed (details will be described later).

The input interface 75 is an operation unit that accepts an examiner's operation. For example, a touch panel, a mouse, a keyboard, and the like may be used as the input interface 75. Such an input interface 75 may be a device separate from SLO1. The control unit 70 controls each of the above members based on an operation signal output from the input interface 75 (operation unit).

<Description of operation>
Next, the operation of the SLO 1 according to the embodiment will be described with reference to FIG. The SLO 1 acquires (captures) a captured image of the fundus image after various adjustments are made. For convenience, in the following description, it is assumed that a still image having a pixel number of 2048 × 2048 is acquired as a captured image unless otherwise specified. In addition, an image having 1024 × 1024 pixels is acquired as an observation image. However, the present invention is not necessarily limited to this, and the number of pixels of the photographed image may be appropriately selected according to the photographing mode, use of the photographed image, and the like.

First, in this embodiment, the positional relationship between the apparatus and the eye to be examined is adjusted (aligned). In the present embodiment, the alignment is performed in a state where the subject faces the SLO1 so that the eye to be examined is arranged in front of the examination window. Various methods can be considered for the alignment. Here, a method using an observation image (moving image) of the eye to be examined is introduced. For example, in this embodiment, an image (observation image) acquired through the photographing optical system 10 is used in alignment. In this case, acquisition and display of an observation image are started by the control unit 70 (S2), and various processes for alignment are executed (S3). In this case, for example, an alignment projection optical system that projects an alignment index light beam onto the corneal surface may be provided in the SLO1. The emission position of the index light beam may be a conjugate position with the center of the radius of curvature of the cornea and the midpoint of the corneal surface when the working distance is appropriate. In such a configuration, the index image by the index light beam is reflected in the image obtained through the photographing optical system at and around the proper working distance. By adjusting the positional relationship between the apparatus and the eye to be examined with respect to the direction intersecting the working distance direction according to the position where the index image is formed on the observation image, alignment in the vertical and horizontal directions can be performed. Moreover, alignment in the working distance direction can be performed by adjusting the positional relationship between the apparatus and the eye to be examined with respect to the working distance direction according to the degree of blurring of the index image. For more details, refer to “Japanese Unexamined Patent Application Publication No. 2016-022261” by the present applicant. The control unit 70 may detect the alignment state with respect to at least one of the working distance direction and the direction intersecting the working distance direction based on an index image included in the observation image.

Note that the present invention is not necessarily limited to this, and an anterior ocular segment observation image (not shown) acquired by an anterior ocular segment observation system (anterior segment camera) (not shown) may be used for alignment. The device and the eye to be examined are adjusted to a positional relationship suitable for fundus photographing by moving the housing containing the photographing optical system with respect to the eye E while confirming the observation image of the anterior eye portion. May be.

Alignment as described above may be manual alignment that is manually adjusted by an examiner, or may be an automatic alignment method that is automatically adjusted by the control unit 70. In the auto alignment method, an actuator for adjusting the positional relationship between the imaging optical system 10 and the eye E so that the imaging optical system 10 and the eye E to be examined have a positional relationship suitable for imaging corresponds to the observation image. The drive is controlled by the controller 70.

Next, autofocus (diopter correction of the photographing optical system) is performed. First, the control unit 70 switches the number of pixels of the fundus image formed as the observation image. More specifically, the number of pixels is set smaller than that of the captured image (S4). Here, the fundus image having the number of pixels of 512 × 512 is set so as to be obtained as an observation image. Accordingly, the fundus image per frame is acquired in a shorter time than the captured image. In this state, diopter correction processing is executed (S5).

In the diopter correction process (S5), the control unit 70 controls the lens 14 to change the diopter correction amount and controls an observation image acquired at any time based on signals from the

light receiving elements

25, 27, and 29. The imaging state in each of these is evaluated.

For example, the control unit 70 may differentiate the image data of the observation image, and may evaluate the imaging state using differential histogram information based on the result of the differentiation process. The differential histogram information may be acquired as a histogram of the contour image after converting the image data of the observation image into a contour image by applying a filter for edge extraction (for example, Laplacian conversion, SOBEL, etc.), for example.

FIG. 8 is a diagram showing an example of the differential histogram. In FIG. 8, the horizontal axis represents the absolute value of differentiation (hereinafter abbreviated as differential value) d (d = 1, 2,... 254), and the vertical axis represents the corresponding number of pixels H (d) in each differential value. In addition, normalized values ((H (d) / H (dp)) of the number of pixels H (dp) in the differential value at which the number of pixels showed a peak are expressed in percentage (%). The histogram of 8 excludes the data of the two end points (d = 0, d = 255), where the differential value d represents the luminance value in the contour image in 255 gradations. .

Here, the control unit 70 uses the maximum value of the luminance value (differential value) having the number of pixels equal to or higher than a predetermined ratio in the entire image in the histogram information acquired as described above (SLO fundus image formation state ( Focus state) Evaluation value is calculated. For example, as the imaging state evaluation value C1 for evaluating the imaging state of the SLO fundus image, the difference between the maximum value Dmax and the minimum value Dmin of the differential value at a threshold S1 (for example, 20%) or more in the differential histogram is obtained. (C1 = Dmax−Dmin). The threshold value S1 is set to a value such that the evaluation value C1 changes sensitively to changes in the imaging state of the SLO fundus image while avoiding the influence of noise. In the above description, only the maximum differential value Dmax above the threshold S1 may be set as the imaging state evaluation value C1.

The imaging state evaluation value C1 shows a high value when the lens 14 is in the in-focus position (when the photographing optical system is in focus), and decreases as the lens 14 deviates from the in-focus position. It can be used to determine the focus state (image formation state) in SLO1.

The control unit 70 samples the imaging state evaluation value C1 while moving the position of the lens 14, determines the in-focus state based on the sampling result, and drives the lens 14 to the in-focus position.

For example, in order to search for an appropriate focus position, the control unit 70 drives and controls the drive mechanism 40a to move the lens 14 to a plurality of discretely set movement positions within the movable range of the lens 14. Acquire a fundus image at the moving position. For example, -12D to + 12D
The lens 14 is moved within the range of. Then, the control unit 70 creates a differential histogram of each fundus image acquired for each movement position, and calculates an imaging state evaluation value C1. In this case, the control unit 70 may continuously move the lens 14 and continuously calculate the imaging state evaluation value C1.

The imaging state evaluation value C1 is a jump value for each position of the lens 14 on which sampling has been performed. The control unit 70 may select a position having the largest imaging state evaluation value C1 as the in-focus position from the positions of the lens 14 where sampling has been performed. However, it is not necessarily limited to this. For example, the imaging state evaluation value C1 corresponding to the intermediate position of each lens 14 that has been sampled may be derived by performing interpolation processing such as curve approximation on the sampling result. Then, a more accurate in-focus position may be estimated from the result of the interpolation process. In addition, as a method for detecting the in-focus position by the interpolation process as described above, a function approximation, a center of gravity, an average value calculation, or the like may be used.

As described above, autofocus is roughly performed using a fundus image having a relatively small number of pixels. Further, in this embodiment, after that, more precise autofocus may be performed using a fundus image having a larger number of pixels. That is, the control unit 70 increases the number of pixels of the fundus image formed as the observation image when rough autofocus is executed. In the case of the present embodiment, since the fundus image having 512 × 512 pixels is used in rough autofocus, for example, the control unit 70 has any number of pixels of 1024 × 1024, 2048 × 2048, 4096 × 4096. To form a fundus image. Then, while moving the lens 14 in the vicinity of the in-focus position obtained by rough autofocus, the imaging state of each fundus image obtained with the movement of the lens 14 is evaluated (in this embodiment, the result is An image state evaluation value C1 is obtained). Then, for example, the in-focus position may be detected again by comparing the image formation state of the fundus image at each position of the lens 14 with each other. By moving the lens 14 to this in-focus position, the focus adjustment in this embodiment is completed. In this embodiment, after the focus adjustment is completed, the control unit 70 sets the number of pixels of the observation image to 1024 × 1024 (S7).

Note that when the imaging state evaluation value C1 is sampled as described above, the movement of the lens 14 may be stopped when the imaging state evaluation value C1 starts to decrease after the increase.

The diopter correction start trigger may be, for example, that the control unit 70 has automatically detected completion of alignment, or that a predetermined operation has been input by the examiner.

Thereafter, other shooting conditions are set (S8). For example, an examiner's operation is input to specify imaging conditions. For example, an imaging method selected from infrared imaging, color imaging, IA (indocyanine green fluorescence imaging), FA (fluorescein fluorescence imaging), and FAF (fundus autofluorescence imaging) is selected, and the selected imaging method is selected. The control unit 70 may set the shooting conditions corresponding to. Specific examples of imaging conditions include laser light wavelength, illumination light quantity, received light signal gain, and the like.

The control unit 70 captures a fundus image based on a trigger signal (for example, a release operation signal or the like). The shooting conditions and image forming conditions at the time of capture reflect the results of various adjustments so far. For example, in the present embodiment, the in-focus position at the time of capture is a position set by adjustment by the process of S5. As described above, in the present embodiment, a still image having the number of pixels: 2048 × 2048 is acquired as a result of the eyelid capture.

In the fundus image, when a shift between the pixel row by the forward scan and the pixel row by the backward scan becomes a problem, an image in which the shift is corrected may be acquired as a result of the capture.

As mentioned above, although it demonstrated based on embodiment, when implementing this indication, the content of embodiment can be changed suitably.

For example, in the embodiment, the focus (the diopter of the apparatus) has been described as being adjusted based on the second image. However, the present invention is not necessarily limited to this, and the second image is adjusted when other conditions are adjusted. May be used. For example, a positional shift between a pixel row by forward scanning and a pixel row by backward scanning may be detected based on the second image. Further, the positional relationship between the eye to be examined and the imaging optical system (SLO1 alignment state) may be detected based on the second image. The control unit 70 may switch the image acquisition control so that the second image is temporarily acquired as an observation image when performing each detection. Thereby, each condition is easily adjusted in a short time.

Further, for example, in the above embodiment, the diopter adjustment unit 40 is driven when correcting the reading timing of the pixels in the forward scanning and the backward scanning using the reflected image of the lens. And shooting becomes difficult. Therefore, for example, the SLO 1 may further include a second correction control process for detecting and correcting a deviation between the first pixel row and the second pixel row based on the image of the eye to be examined. For example, the second correction control process may be repeatedly executed at regular intervals during the acquisition of the observation image. On the other hand, the correction process using the reflected image of the lens is an imaging method in which imaging is performed continuously with a different imaging method when the apparatus is started up, when the subject is changed, and when the apparatus returns from the sleep state. It may be executed at the time of switching.

When the deviation between the first pixel row and the second pixel row is detected and corrected based on the image of the eye to be examined, the detection and correction of the deviation need not be performed every time the image of the eye to be examined is acquired. No. For example, when the acquired image is displayed or analyzed, the image of the eye to be examined acquired in advance may be processed to detect and correct the deviation. In this case, the correction amount of the shift in each eye image may be set based on a plurality of frames of the eye image obtained in time series.

For example, as described above, the SLO 1 according to the embodiment may be integrated with an optical coherence tomography (OCT). In this case, the control unit 70 may reflect the above-described focus adjustment result of SLO1 on the OCT optical system. Specifically, at least the diopter adjustment unit 40 may be shared by the SLO1 photographing optical system and the OCT optical system. In addition, the diopter adjustment unit in the OCT optical system is not limited thereto, and may be a separate body from the diopter adjustment unit 40 of SLO1. In this case, for example, the diopter adjusting unit in the OCT optical system is mechanically linked to the diopter adjusting unit 40 of SLO1 and the diopter adjusting unit 40 of SLO1 so that the diopter correction amounts are the same as each other. It may be.

DESCRIPTION OF SYMBOLS 10 Irradiation optical system 11 Light source 16 Scan part 20 Light reception

optical system

25,27,29 Light receiving element 70 Control part

Claims

An imaging optical system having an irradiation optical system that irradiates the eye to be examined while scanning light from a light source by a scanning unit, and a light receiving optical system that has at least a light receiving element that receives return light from the eye to be examined;
Image forming means for acquiring a captured image of the eye to be examined based on a signal from the light receiving element;
A second image having a smaller number of pixels than the captured image or a time required for forming an image per frame compared to the captured image is formed in the image forming means, and at least a condition regarding the captured image is set. Condition setting means for setting one based on the second image;
An ophthalmic imaging apparatus comprising: an imaging execution unit that captures the captured image according to the set condition.
The condition setting means forms a plurality of the second images while temporarily changing the at least one condition after the condition adjustment start trigger is issued, and the plurality of the second images. The ophthalmologic photographing apparatus according to claim 1, wherein the condition is set based on the condition.
3. The ophthalmologic photographing apparatus according to claim 1, wherein the condition setting unit causes the image forming unit to acquire the second image by making the operation of the scanning unit different from that at the time of acquiring the captured image.
4. The ophthalmic imaging apparatus according to claim 1, wherein the condition is a focus adjustment amount of the ophthalmic imaging apparatus.
4. The ophthalmologic photographing apparatus according to claim 1, wherein the condition is at least one of an output of light from the light source and an amplification factor of a signal from the light receiving element.
The said condition setting means makes the said image formation means acquire the said 2nd image by making at least one of the scanning range and scanning speed in the said scanning part differ with respect to the time of acquisition of the said picked-up image. Ophthalmic photography device.
The scanning unit includes at least an optical scanner for scanning the light in the sub-scanning direction on the eye to be examined.
The ophthalmologic photographing apparatus according to claim 6, wherein the condition setting unit causes the image forming unit to acquire the second image by adjusting at least one of a scanning range and a scanning speed in the sub-scanning direction.
The condition setting means forms the second image by adjusting a scanning speed in the sub-scanning direction,
Further, the condition setting unit performs rough adjustment of the condition based on the second image, and then performs fine adjustment by the image forming unit, and has a larger number of pixels than the second image. The ophthalmologic photographing apparatus according to claim 7, which is performed based on three images.