Ophthalmic device

Abstract

This ophthalmic device performs an examination of an eye to be examined. The ophthalmic device comprises an irradiation optical system, a sensor, and a control unit. The irradiation optical system irradiates the eye to be examined with irradiation light. The sensor receives reflected light from the eye to be examined, the light being the irradiation light irradiated by the irradiation optical system. The control unit governs control of the ophthalmic device. The sensor is an event-based sensor that detects and outputs, for each pixel, a change exceeding a threshold value of the luminance of the received light. The control unit acquires analysis information indicating at least one of a position, a displacement, a shape, and a tissue state pertaining to the eye to be examined, on the basis of information output by the event-based sensor.

Description

ophthalmology equipment

[0001] The present disclosure relates to an ophthalmologic apparatus that examines an eye to be examined while its relative position with respect to the eye to be examined is adjusted.

[0002] Various ophthalmic devices are known for performing examinations of a subject's eye (e.g., at least one of photographing, observing, measuring, and detecting). Examples of known ophthalmic devices include an eye refractive power measuring device, a corneal curvature measuring device, an intraocular pressure measuring device, a fundus camera, an OCT device, and a scanning laser ophthalmoscope (SLO). Other ophthalmic devices (e.g., a laser treatment device and a cataract surgery device) treat or operate on the subject's eye while allowing an examiner to observe the eye. Examinations of the subject's eye using many ophthalmic devices must be performed with the relative position between the subject's eye and an ophthalmic examination unit provided in the ophthalmic device adjusted to an appropriate position.

[0003] Conventional ophthalmic apparatuses are equipped with two-dimensional imaging elements (e.g., CMOS image sensors) for various purposes. For example, the ophthalmic apparatus described in Patent Document 1 includes a two-dimensional imaging element that captures an image of the anterior segment of the subject's eye and an irradiation optical system that projects an alignment target onto the cornea of ​​the subject's eye. Alignment of the optometry unit with respect to the subject's eye is performed based on the position of the alignment target in the anterior segment image.

[0004] Japanese Patent Application Laid-Open No. 2020-124350

[0005] Conventional methods using two-dimensional imaging elements have sometimes resulted in inappropriate examination of the subject's eye. For example, in addition to reflections of light irradiated onto the subject's eye by the illumination optical system, reflections of unwanted ambient light may also appear in the image captured by the two-dimensional imaging element. When reflections of ambient light appear in the image, it becomes difficult to properly examine the subject's eye. Furthermore, an insufficient frame rate of the video captured by the two-dimensional imaging element may result in inappropriate examination of the subject's eye. An insufficient amount of light received by the two-dimensional imaging element, insufficient image contrast, and the like may also result in inappropriate examination. Therefore, there is a demand for an ophthalmic apparatus that can more appropriately examine the subject's eye.

[0006] A typical object of the present disclosure is to provide an ophthalmologic apparatus capable of more appropriately examining a subject's eye by solving at least one of the above problems.

[0007] An ophthalmic device provided by a typical embodiment of the present disclosure is an ophthalmic device for examining a test eye, and includes an irradiation optical system that irradiates the test eye with irradiation light, a sensor that receives light reflected by the test eye from the irradiation light irradiated by the irradiation optical system, and a control unit, wherein the sensor is an event-based sensor that detects and outputs changes in the brightness of the received light that exceed a threshold value for each pixel, and the control unit obtains analytical information indicating at least one of the position, displacement, shape, and tissue state of the test eye based on the information output by the event-based sensor.

[0008] According to the ophthalmologic apparatus according to the present disclosure, examination of the subject's eye can be performed more appropriately.

[0009] The ophthalmic apparatus exemplified in the present disclosure examines a subject's eye. The ophthalmic apparatus includes an irradiation optical system, a sensor, and a control unit. The irradiation optical system irradiates the subject's eye with irradiation light. The sensor receives light reflected by the subject's eye from the irradiation light irradiated by the irradiation optical system. The control unit controls the ophthalmic apparatus. The sensor is an event-based sensor that detects and outputs changes in the brightness of the received light that exceed a threshold for each pixel. The control unit obtains analytical information indicating at least one of the position, displacement, shape, and tissue state of the subject's eye based on information output by the event-based sensor.

[0010] The event-based sensor included in the ophthalmic device disclosed herein detects and outputs changes in the luminance of light received by each pixel (changes exceeding a positive or negative threshold), rather than the magnitude of the luminance of the light received by each pixel. Each pixel operates independently and immediately outputs information when it detects a change in the luminance of the received light that exceeds a threshold. As a result, changes in luminance exceeding the threshold are detected and output at ultra-high speed. Therefore, the event-based sensor detects changes in luminance with higher time resolution than conventionally used two-dimensional imaging elements. Furthermore, by utilizing the characteristics of the event-based sensor, which outputs changes in luminance rather than information on the magnitude of light, the control unit can obtain highly accurate analytical information (e.g., analytical information in which the influence of unnecessary ambient light with a substantially constant luminance is suppressed). Furthermore, the dynamic range of the event-based sensor is wider than that of conventionally used two-dimensional imaging elements, making it less susceptible to effects such as insufficient light intensity and contrast. Therefore, the use of the event-based sensor facilitates more appropriate examination of the subject's eye.

[0011] The event-based sensor (sometimes referred to as a "brightness value difference output sensor," "event-based vision sensor," etc.) disclosed herein detects changes over time in the brightness of light incident on each pixel and outputs information about the pixel whose brightness has changed asynchronously with that of other pixels. The information output from the event-based sensor may include, for example, position information indicating the position coordinates of the pixel where the brightness change occurred, positive / negative information indicating whether the brightness change is positive or negative (whether the brightness change is an increase or decrease), and time information indicating the time (or timing) when the brightness change occurred.

[0012] At least a portion of the techniques exemplified in the present disclosure can be applied to various ophthalmic devices that perform examinations of a subject's eye (e.g., at least one of photographing, observing, measuring, and detecting). For example, at least a portion of the techniques exemplified in the present disclosure may be applied to an eye refractive power measurement device, a corneal curvature measurement device, an intraocular pressure measurement device, a corneal thickness measurement device, a fundus camera, an OCT device, a laser scanning ophthalmoscope (SLO), a retinal observation device, a corneal endothelial cell photographing device, a goniography device, etc. Furthermore, at least a portion of the techniques exemplified in the present disclosure can also be applied to an ophthalmic device that performs examinations of a subject's eye (e.g., photographing or observing) and treatments or surgeries on the subject's eye.

[0013] The illumination optical system may perform flashing illumination by flashing illumination light to be irradiated onto the subject's eye while acquiring the analysis information. The control unit may acquire, as the analysis information, information on the distribution of light reflection characteristics of the subject's eye based on information output by the event-based sensor while flashing illumination is being performed by the illumination optical system.

[0014] An event-based sensor outputs changes in the luminance of the received light, but if the luminance of the received light does not change, no information is output even if there is a difference in luminance within the light-receiving area. In contrast, when the irradiated light is flashed, the luminance of the received light changes between when the light is on and when it is off at the area where the irradiated light is reflected in the direction received by the event-based sensor (i.e., the area where the irradiated light is reflected toward the event-based sensor). On the other hand, at the area where the irradiated light is not reflected toward the event-based sensor, the luminance of the received light naturally does not change even if the irradiated light is flashed. In other words, by flashing the irradiated light, the distribution of the light reflection characteristics of the test eye (e.g., whether or not light is reflected toward the event-based sensor) is reflected in the output result from the event-based sensor.

[0015] Therefore, by flashing the irradiated light, the ophthalmologic apparatus can appropriately acquire analytical information regarding the distribution of light reflection characteristics in the subject's eye based on the information output by the event-based sensor. Furthermore, by acquiring analytical information based on the output of the event-based sensor, the influence of unnecessary ambient light is suppressed, unlike when a two-dimensional imaging element is used. Therefore, the examination of the subject's eye can be more appropriately performed.

[0016] When flashing illumination is performed, the rate at which the light is switched on and off (the number of times the light is switched on and off per unit time) may be set to be higher than the frame rate (typically 100 fps) that can be achieved by a two-dimensional imaging element used in conventional ophthalmic devices. In this case, changes in luminance can be detected with a higher time resolution than in conventional ophthalmic devices that use a two-dimensional imaging element such as a general CMOS image sensor.

[0017] The control unit may acquire information on the distribution of light reflectance characteristics by processing information output by the event-based sensor at a rate corresponding to the rate at which the flashing illumination by the illumination optical system is switched on and off. In this case, processing of the information output by the event-based sensor is repeatedly performed at appropriate timing corresponding to the rate at which the illumination light is switched on and off. Therefore, information on the distribution of light reflectance characteristics is acquired with high time resolution. Furthermore, even when unnecessary disturbance light is flashing, if the flashing rate of the disturbance light and the flashing rate of the illumination light differ, the output information from the event-based sensor is processed according to the flashing rate of the illumination light, making it difficult for the influence of the disturbance light to be reflected in the analysis information. Therefore, it becomes easier to perform an examination of the subject's eye more appropriately.

[0018] The rate at which the information output from the event-based sensor is processed may be the same as the rate at which the irradiated light is switched on and off (i.e., N = 1). In this case, the influence of unwanted ambient light can be more easily eliminated when obtaining information about the distribution of light reflectance characteristics.

[0019] The irradiation optical system may include a plurality of light sources that emit irradiation light. The blinking periods of at least two of the light sources may be different from each other. In this case, the information on the distribution of the light reflection characteristics changes for each light source depending on the blinking period of each of the plurality of light sources. Therefore, the distribution of the light reflection characteristics (e.g., the distribution of reflection positions, which will be described later) can be distinguished for each light source that emits reflected light. This facilitates more appropriate examination of the subject's eye.

[0020] Note that a specific method for changing the blinking cycle of each of the plurality of light sources can be selected as appropriate. For example, the timing at which the blinking cycle is repeated (the timing at which the light is turned on and off) may be changed among the plurality of light sources. Also, the length of the blinking cycle may be changed among the plurality of light sources.

[0021] Furthermore, at least two types of light sources whose blinking cycles are changed can be appropriately selected. For example, the blinking cycles may be changed between a light source that emits finitely distant light toward the cornea and a light source that emits infinitely distant light toward the same cornea. In this case, the distribution of reflection positions of finitely distant light on the cornea and the distribution of infinitely distant light can be appropriately distinguished.

[0022] The illumination optical system may perform increasing and decreasing illumination by increasing and decreasing the intensity of illumination light irradiated onto the subject's eye over time while acquiring the analysis information. The control unit may acquire, as the analysis information, information on the distribution of light reflection characteristics of the subject's eye based on information output by the event-based sensor while the illumination optical system is performing increasing and decreasing illumination.

[0023] As described above, an event-based sensor outputs changes in the luminance of received light. However, if the luminance of the received light does not change, no information is output even if there is a difference in luminance within the light-receiving area. In contrast, when the intensity of the irradiated light is increased or decreased linearly over time, the luminance of the received light changes in areas where the irradiated light is reflected toward the event-based sensor. On the other hand, in areas where the irradiated light is not reflected toward the event-based sensor, the luminance of the received light naturally does not change even if the intensity of the irradiated light is increased or decreased. In other words, by increasing or decreasing the intensity of the irradiated light, the distribution of the light reflection characteristics of the test eye (e.g., whether or not light is reflected toward the event-based sensor) is reflected in the output result from the event-based sensor.

[0024] Therefore, by increasing or decreasing the intensity of the irradiated light, the ophthalmic device can appropriately acquire analytical information regarding the distribution of light reflection characteristics in the subject's eye based on the information output by the event-based sensor. Furthermore, by acquiring analytical information based on the output of the event-based sensor, analytical information is acquired with the influence of unnecessary ambient light suppressed, unlike when using a two-dimensional imaging element. Furthermore, even though the intensity of the irradiated light is increased or decreased, the irradiated light continues to be emitted, so the control unit can continuously acquire analytical information with high time resolution. This makes it easier to perform a more appropriate examination of the subject's eye.

[0025] The event-based sensor may output positive / negative information for each pixel indicating whether the change in luminance is an increase or decrease. The illumination optical system may include multiple light sources that emit illumination light. The timing at which the intensity of the illumination light of at least two light sources increases or decreases (light intensity increase / decrease timing) may differ from each other. In this case, the positive / negative information output by the event-based sensor varies for each light source depending on the timing at which the light intensity of each of the multiple light sources increases or decreases. As a result, the acquired information on the distribution of light reflection characteristics varies for each light source. Therefore, the distribution of light reflection characteristics (e.g., the distribution of reflection positions, described below) can be distinguished for each light source that emits reflected light. It is also possible to distinguish and detect different detection targets. This facilitates more appropriate examination of the subject's eye.

[0026] Note that a specific method for changing the timing for increasing or decreasing the light intensity of each of the multiple light sources can be selected as appropriate. For example, when two types of light sources are provided (e.g., at least one light source emitting finitely distant light and at least one light source emitting infinitely distant light), the timing for increasing or decreasing the light intensity of each of the light sources can be set so that the period for increasing the light intensity of one type of light source coincides with the period for decreasing the light intensity of the other type of light source. In this case, the positive / negative information of one type of light source and the positive / negative information of the other type of light source are reversed. This makes it easier to more accurately distinguish the distribution of light reflectance characteristics according to the type of light source.

[0027] Furthermore, the types of at least two light sources for which the timing for increasing or decreasing the light intensity can be changed can be appropriately selected. For example, the timing for increasing or decreasing the light intensity can be changed between a light source that emits irradiation light at a finite distance toward the cornea and a light source that emits irradiation light at an infinite distance toward the same cornea. In this case, the distribution of the reflection positions of the irradiation light at a finite distance on the cornea and the distribution of the reflection positions of the irradiation light at an infinite distance can be appropriately distinguished.

[0028] The illumination optical system may illuminate the cornea of ​​the subject's eye with light. The event-based sensor may be positioned to receive light reflected by the cornea of ​​the subject's eye. The control unit may acquire, as the analysis information, information on a distribution of reflection positions on the cornea of ​​the subject's eye where the illumination light emitted by the illumination optical system is reflected in a direction received by the event-based sensor.

[0029] Assuming that the event-based sensor is replaced with a two-dimensional imaging element, an index (e.g., a bright spot) is formed on the cornea imaged by the two-dimensional imaging element at a position where the irradiated light is reflected toward the two-dimensional imaging element. The ophthalmic apparatus can perform various controls, such as adjusting the relative position of the optometry unit with respect to the subject's eye (so-called "alignment"), by using the distribution of the positions of the formed corneal index. However, the image of the cornea captured by the two-dimensional imaging element may include not only the corneal index formed by the irradiated light but also an image formed by unnecessary ambient light, making it difficult to accurately detect the position of the corneal index from the image.

[0030] Here, the distribution of positions (reflection positions) on the cornea of ​​the subject's eye where irradiated light is reflected toward the event-based sensor approximates or coincides with the distribution of corneal indices in the captured image when the event-based sensor is replaced with a two-dimensional imaging element. Furthermore, by using the event-based sensor, information on the distribution of reflection positions is acquired while suppressing the effects of ambient light. Therefore, by acquiring analytical information on the distribution of reflection positions on the cornea based on the information output by the event-based sensor, the ophthalmic apparatus can appropriately perform control similar to conventional control using the distribution of corneal indices.

[0031] The ophthalmologic apparatus may further include a two-dimensional imaging element. The two-dimensional imaging element captures an image of at least a region of the subject's eye that overlaps with a region in which a change in light luminance is detected by the event-based sensor. The control unit may superimpose a distribution of light reflection characteristics of the subject's eye (e.g., a luminance change distribution image described below) acquired based on output information from the event-based sensor on the image of the subject's eye captured by the two-dimensional imaging element and display the resulting image on the display unit.

[0032] In this case, the examiner can properly grasp the distribution of reflection characteristics acquired based on the output information of the event-based sensor on the captured image of the subject's eye. Therefore, for example, the examiner can properly perform alignment by manually adjusting the relative position of the optometry unit with respect to the subject's eye while checking the superimposed image.

[0033] In this case, the examiner can properly grasp the distribution of reflection characteristics acquired based on the output information of the event-based sensor on the captured image of the subject's eye. For example, it becomes easier to visually grasp the positional deviation of the distribution of reflection characteristics. Therefore, for example, the examiner can properly perform alignment by manually adjusting the relative position of the optometry unit with respect to the subject's eye while checking the superimposed image. Furthermore, when processing an image of the subject's eye on which the distribution of reflection characteristics is superimposed, processing results (e.g., at least one of the processing results, such as the direction and amount of positional deviation) can be easily obtained with high accuracy.

[0034] A specific method for changing the threshold value depending on the object for which the distribution information of reflection characteristics is to be acquired can be appropriately set. For example, the amount of reflected light from the cornea tends to be greater than the amount of reflected light from other parts of the test eye (e.g., the iris). Therefore, when flashing or increasing / decreasing illumination is performed on the test eye, the amount of change in the reflected light reflected from the cornea toward the event-based sensor tends to be greater than the amount of change in the reflected light reflected from other parts toward the event-based sensor. Therefore, when the object for which the distribution information of reflection characteristics is to be acquired is the cornea, the control unit may set a first threshold value of a predetermined magnitude. On the other hand, when the object for which the distribution information of reflection characteristics is to be acquired includes not only the cornea but also parts other than the cornea, the control unit may set a second threshold value smaller than the first threshold value. Note that the control unit can also identify or separate the distribution information of reflection characteristics for parts of the test eye other than the cornea by comparing the distribution information of reflection characteristics acquired when the second threshold value is set with the distribution information of reflection characteristics acquired when the first threshold value is set. This makes it easier to perform an appropriate examination of the test eye. Furthermore, by using a similar method, it is also possible to distinguish or separate distribution information of reflection positions caused by irradiated light at a finite distance from distribution information of reflection positions caused by irradiated light at an infinite distance.

[0035] Furthermore, when the brightness of the installation environment of the ophthalmologic apparatus changes, the threshold value suitable for acquiring the analytical information also changes. Therefore, the control unit may acquire information about the brightness of the installation environment of the ophthalmologic apparatus and set the threshold value based on the acquired brightness information. In this case, the accuracy of acquiring the analytical information is likely to be improved regardless of changes in the brightness of the installation environment. Furthermore, the control unit may improve the accuracy of acquiring the analytical information by changing the threshold value according to individual differences in the subject's eye.

[0036] The ophthalmic device may include multiple event-based sensors. In this case, the information obtained about the subject's eye can be further diversified, making it easier to perform an appropriate eye examination. For example, by setting different threshold values ​​for the pixels of the event-based sensors to detect changes in light luminance among the multiple event-based sensors, it is possible to simultaneously acquire the distributions of reflectance characteristics for multiple targets, even if there are multiple targets for which the distributions of reflectance characteristics are to be acquired. Furthermore, by arranging the light-receiving optical axes of the multiple event-based sensors at an angle to the examination axis, it is possible to acquire the state of changes in light luminance from multiple directions.

[0037] The ophthalmologic apparatus may further include an optometry unit and an examination position moving unit. The optometry unit performs an examination on the subject's eye. The examination position moving unit moves the examination position of the optometry unit. The event-based sensor may output positive / negative information for each pixel indicating whether a change in luminance that has occurred is an increase or a decrease. The irradiation optical system may constantly irradiate the subject's eye with irradiation light of a constant intensity while acquiring the analysis information. The control unit may acquire, as the analysis information, displacement information indicating a displacement of a specific portion of the subject's eye based on the position of the pixel that output the positive / negative information. The control unit may drive the examination position moving unit based on the acquired displacement information, thereby causing the examination position to follow the displacement of the specific portion. In other words, tracking of the examination position with respect to the specific portion of the subject's eye may be performed based on the displacement information.

[0038] As described above, the event-based sensor detects changes in luminance with a higher temporal resolution than conventional two-dimensional imaging devices. Therefore, the control unit can obtain displacement information (e.g., vector information) indicating the displacement of a specific part of the subject's eye based on the position of the pixel that outputs positive / negative information, thereby grasping the displacement of the subject's eye (e.g., the direction and amount of displacement) with high temporal resolution. Tracking the examination position relative to the specific part based on the obtained displacement information appropriately improves tracking accuracy.

[0039] Tracking based on displacement information can be used to track the examination position relative to the anterior segment of the subject's eye, or to track the examination position relative to the fundus of the subject's eye. Furthermore, when acquiring displacement information, the subject's eye is constantly irradiated with constant-intensity light, allowing for high-time resolution. However, it is also possible to acquire displacement information while performing flashing or increasing / decreasing illumination.

[0040] The specific configuration of the examination position moving unit can be selected as appropriate. For example, the optometry unit may include an irradiation position moving unit (e.g., an optical scanner that changes the deflection direction of light) that moves the irradiation position of light for examination. In this case, the irradiation position moving unit can be used as the examination position moving unit. Furthermore, a relative position moving unit that moves the relative position of the optometry unit with respect to the subject's eye can be used as the examination position moving unit.

[0041] In conventional ophthalmic devices using a two-dimensional imaging element, a light source for capturing an image using the two-dimensional imaging element is installed inside the housing. When the light is irradiated toward the subject's eye through an optical element (e.g., a lens), the reflected light from the optical element may be captured by the two-dimensional imaging element. Therefore, methods such as exposing the light source to the outside of the housing have been adopted. However, when an event-based sensor is used, the change in the luminance of the light received by each pixel (a change exceeding a threshold) is detected, rather than the magnitude of the luminance of the light received by each pixel. Therefore, even if light reflected from an optical element enters the event-based sensor, there is no effect as long as the intensity of the incident reflected light is constant. Therefore, when using a light source that constantly irradiates light with a constant intensity, the ophthalmic device may have the light source installed inside the housing and irradiate the light toward the subject's eye through the optical element. In this case, the light can be appropriately irradiated toward the subject's eye from inside the housing without being affected by the reflected light from the optical element.

[0042] In the event-based sensor, multiple pixels may be arranged in a two-dimensional region intersecting the optical axis of the received light. The control unit may process information output by each of the multiple pixels to generate a luminance change distribution image showing a two-dimensional distribution of changes in luminance of the received light. In this case, the two-dimensional distribution of changes in luminance of the light can be appropriately understood by the luminance change distribution image. Therefore, the distribution of light reflection characteristics in the test eye can be more appropriately understood.

[0043] For example, when the illumination optical system is caused to perform blinking illumination or increasing and decreasing illumination, the luminance change distribution image represents a two-dimensional distribution of the light reflection characteristics of the subject's eye. Therefore, the luminance change distribution image can be treated in the same way as an image captured using a two-dimensional imaging element. That is, the luminance change distribution image can also be used as a substitute for an anterior segment image of the subject's eye captured using a two-dimensional imaging element. For example, the control unit may detect the position of the pupil, which is located at the center of the iris, by processing the luminance change distribution image containing information on the luminance change of light reflected by the iris.

[0044] The installation position of the event-based sensor can also be selected appropriately. For example, the optometry unit may perform an examination of the subject's eye with the examination axis aligned with the subject's eye. The event-based sensor may be provided inside the housing of the ophthalmic device. The light-receiving optical axis of the event-based sensor may be made coaxial with the examination axis by an optical member. In this case, the event-based sensor can appropriately receive light propagating along the examination axis. Furthermore, the light-receiving optical axis of the event-based sensor may be disposed obliquely with respect to the examination axis. The light-receiving optical axis of each of the multiple event-based sensors may be disposed obliquely with respect to the examination axis.

[0045] The method of acquiring and using the analysis information can also be selected as appropriate. For example, the ophthalmologic apparatus may further include an optometry unit and a relative position movement unit. The optometry unit performs an examination on the subject's eye. The relative position movement unit moves the relative position of the optometry unit with respect to the subject's eye. The control unit may acquire, as the analysis information, information on the distribution of reflection positions on the cornea of ​​the subject's eye where irradiated light is reflected in a direction received by the event-based sensor. The control unit may automatically adjust the relative position of the optometry unit with respect to the subject's eye (so-called alignment) by driving the relative position movement unit based on the information on the distribution of reflection positions. In this case, alignment can be performed with high accuracy while suppressing the effects of unnecessary ambient light, etc.

[0046] It is also possible to use information about the distribution of reflection positions when the alignment of the optometry unit with respect to the subject's eye is performed manually by the examiner. For example, the control unit may cause the subject to manually perform alignment by displaying an image related to the acquired distribution of reflection positions (e.g., an image showing the distribution of reflection positions, or a two-dimensional image of the subject's eye superimposed with the distribution of reflection positions) on the display unit.

[0047] Furthermore, as described above, the control unit may detect the position of the pupil located at the center of the iris by processing distribution information of the reflection characteristics of light reflected by the iris (which may be a luminance change distribution image including information on luminance changes in light reflected by the iris). The control unit may automatically adjust the position (alignment) of the optometry unit relative to the pupil of the subject's eye by driving the relative position moving unit based on the information on the pupil position. This also makes it easier to perform alignment with high accuracy.

[0048] The luminance change distribution image may also be used when the alignment of the optometry unit with respect to the subject's eye is performed manually by the examiner. For example, the control unit may cause the subject to manually perform the alignment by displaying the luminance change distribution image or a two-dimensional image of the subject's eye superimposed on the luminance change distribution image on the display unit.

[0049] The control unit may process distribution information of the reflection characteristics of light reflected by a specific tissue (e.g., the crystalline lens) of the subject's eye that may be opacified, or a brightness change distribution image including information on the brightness change of the light reflected by the specific tissue, to obtain analytical information indicating the state of the specific tissue (e.g., whether or not opacification has occurred in the specific tissue, or the degree of opacification in the specific tissue). If no opacification has occurred, the intensity of the light reflected by the specific tissue will be low, but the more opacification there is, the greater the intensity of the light reflected by the specific tissue. Therefore, by processing the distribution information of the reflection characteristics or the brightness change distribution image, the state of opacity in the specific tissue can be appropriately determined. Furthermore, the control unit may process the distribution information of the reflection characteristics or the brightness change distribution image to obtain information on the location of opacification in the specific tissue as analytical information.

[0050] Furthermore, the front and back surfaces of the cornea have different reflectances for light irradiated from outside the cornea. Therefore, by appropriately adjusting the threshold for detecting changes in light brightness by the pixels of the event-based sensor, it is possible to acquire distribution information of the reflectance characteristics of only the front surface of the cornea, or to acquire distribution information of the reflectance characteristics of both the front and back surfaces of the cornea. For example, the control unit may acquire distribution information of the reflectance characteristics of the front surface of the cornea by setting a third threshold of a predetermined magnitude. The control unit may acquire distribution information of the reflectance characteristics of both the front and back surfaces of the cornea by setting a fourth threshold smaller than the third threshold. The control unit may acquire the position or shape, etc., of the back surface of the cornea by comparing the distribution information of the reflectance characteristics acquired when the fourth threshold is set with the distribution information of the reflectance characteristics acquired when the third threshold is set.

[0051] FIG. 1 is a side view showing the external configuration of an ophthalmic apparatus 1 of a first embodiment. FIG. 2 is a schematic diagram of an optical system provided in an optometry unit 12 of the ophthalmic apparatus 1 of the first embodiment. FIG. 3 is a schematic diagram of an event-based sensor 20 and an enlarged single pixel 21 viewed from the light-receiving area side. FIG. 4 is a flowchart of a first examination process performed by the ophthalmic apparatus 1 of the first embodiment. FIG. 5 is a diagram showing an example of a superimposed image of luminance change distribution images generated in the first examination process. FIG. 6 is a flowchart of a second examination process performed by the ophthalmic apparatus 1 of the first embodiment. FIG. 7 is a diagram showing an example of a superimposed image of luminance change distribution images generated in the second examination process. FIG. 8 is a diagram showing a schematic configuration of an ophthalmic apparatus 60 of a second embodiment. FIG. 9 is a flowchart of a tracking process performed by the ophthalmic apparatus 60 of the second embodiment.

[0052] First Embodiment A first embodiment, which is one of typical embodiments according to the present disclosure, will be described below. An ophthalmic apparatus 1 examines an eye E. The ophthalmic apparatus 1 of the first embodiment projects measurement light onto the fundus of the eye E and measures characteristics of the eye E (e.g., at least one of ocular refractive power and aberration) based on the reflected measurement light from the fundus. That is, in the first embodiment, an ophthalmic apparatus for examining the eye E is exemplified as an ophthalmic apparatus for examining the eye E. However, at least a portion of the techniques exemplified in the present disclosure can also be applied to ophthalmic apparatuses other than ophthalmic refractive power measurement apparatuses (e.g., corneal curvature measurement apparatuses, ocular pressure measurement apparatuses, corneal thickness measurement apparatuses, fundus cameras, OCT apparatuses, laser scanning ophthalmoscopy (SLO), retinal observation apparatuses, corneal endothelial cell imaging apparatuses, goniophotography apparatuses, surgical apparatuses, treatment apparatuses, etc.). The examination of the eye E is performed with the eye E and the examination axis LA relatively aligned.

[0053] (External Configuration) An example of the external configuration of the ophthalmic apparatus 1 of the first embodiment will be described with reference to Fig. 1. The ophthalmic apparatus 1 of the first embodiment includes a base 11, an eye examination unit 12, a relative position movement unit 13, a face support unit 15, a monitor 16, an operation unit 17, and a control unit 50.

[0054] The base 11 supports the entire ophthalmic apparatus 1. The optometry unit 12 houses the optical system and other components used to examine the subject's eye E. The face support unit 15 is fixed to the base 11. The face support unit 15 supports the subject's face to fix the position of the subject's eye E. The relative position movement unit 13 moves the optometry unit 12 relative to the base 11 in the X direction (left-right direction), Y direction (up-down direction), and Z direction (front-back direction), thereby changing the relative position of the optometry unit 12 (more specifically, the examination axis LA (see FIG. 2 ) extending from the optometry unit 12 toward the subject's eye E) with respect to the subject's eye E. The monitor 16 can display various information. The operation unit 17 is operated by a user to input instructions from the user to the control unit 50. As an example, the operation unit 17 in the first embodiment is a touch panel provided on the monitor 16. The control unit 50 controls the ophthalmic apparatus 1.

[0055] (Optical System) An example of the schematic configuration of the optical system included in the ophthalmic examination unit 12 of the ophthalmic apparatus 1 will be described with reference to FIGS. 2 and 3 . In this disclosure, the term "conjugate position" also includes a substantially conjugate position. "Substantially conjugate" does not necessarily mean that the positions are completely conjugate, but rather that they are conjugate with the required accuracy in relation to measurement accuracy. Furthermore, "nearby" means that the positions are close to each other with the required accuracy in relation to measurement accuracy. The ophthalmic examination unit 12 of the ophthalmic apparatus 1 of the first embodiment includes a measurement optical system 100, a fixation target presenting optical system 150, a luminance change detection optical system 200, an irradiation optical system 400, and the like. The ophthalmic examination unit 12 also includes half mirrors 501 and 502 that branch and combine the optical paths of the respective optical systems, an objective lens 505, and the like.

[0056] (Measurement Optical System) The measurement optical system 100 is used to objectively measure characteristics (e.g., ocular refractive power) of the subject's eye E. The measurement optical system 100 includes a light-projecting optical system 110 and a light-receiving optical system 120. The light-projecting optical system 110 projects measurement light onto the fundus of the subject's eye E via an objective lens 505. As an example, the light-projecting optical system 110 of the first embodiment projects spot-shaped measurement light onto the fundus of the subject's eye E through the center of the pupil of the subject's eye E. The light-receiving optical system 120 causes the light-receiving element 126 to receive the reflected light of the measurement light that is reflected by the fundus and passes through the pupil and the objective lens 505.

[0057] The projection optical system 110 includes a measurement light source 111, a relay lens 112, a hole mirror 113, an objective lens 505, and the like, all arranged on an optical axis L1. The measurement light source 111 is disposed at a fundus-conjugate position on the optical axis L1 of the projection optical system 110 and emits measurement light for measuring the characteristics of the subject's eye E. The measurement light source 111 may be, for example, a superluminescent diode (SLD) light source or a light-emitting diode (LED) light source. The measurement light source 111 of the first embodiment is an infrared light source that emits infrared light. As an example, the measurement light source 111 of the first embodiment emits near-infrared light having a peak wavelength between 800 nm and 900 nm as measurement light. The opening of the hole mirror 113 is disposed at a pupil-conjugate position. The measurement light emitted by the measurement light source 111 passes through the relay lens 112, the opening of the hole mirror 113, the half mirror 502, the half mirror 501, and the objective lens 505, and is projected onto the fundus of the eye E to be examined.

[0058] The light-receiving optical system 120 includes an objective lens 505, a hole mirror 113, relay lenses 121 and 122, a light-receiving diaphragm 123, a collimator lens 124, a ring lens 125, and a light-receiving element 126, all arranged on an optical axis L2. Reflected light from the fundus, which is necessary for measuring the characteristics of the subject's eye E, passes through the objective lens 505, the half mirror 501, and the half mirror 502, is reflected by the hole mirror 113, and passes through the relay lens 121, the light-receiving diaphragm 123, the collimator lens 124, and the ring lens 125 before being received by the light-receiving element 126. The light-receiving diaphragm 123 is positioned at a conjugate position with the fundus. The ring lens 125 is positioned at a conjugate position with the pupil of the subject's eye E. The light-receiving element 126 is positioned at a conjugate position with the fundus.

[0059] The hole mirror 113 passes the measurement light emitted by the measurement light source 111 of the light-projecting optical system 110 through an opening, and reflects the measurement light reflected from the fundus. As a result, the optical axis L1 of the light-projecting optical system 110 and the optical axis L2 of the light-receiving optical system 120 are made coaxial by the hole mirror 113. Furthermore, the hole mirror 113 passes, through an opening, the corneal reflected light reflected by the cornea of ​​the subject's eye E and traveling along the optical axis L2 of the light-receiving optical system 120 toward the light-receiving element 126. Therefore, the hole mirror 113 is an example of a corneal reflected light removing unit that removes the corneal reflected light traveling along the optical axis L2 of the light-receiving optical system 120 toward the light-receiving element 126.

[0060] The light receiving optical system 120 of the first embodiment also includes a mask 130. The mask 130 is disposed at a conjugate position with respect to the pupil of the subject's eye E, thereby blocking light within a predetermined range including the optical axis L2, of light traveling along the optical axis L2 of the light receiving optical system 120 toward the light receiving element 126. The mask 130 is an example of a corneal reflection light removing unit that removes corneal reflection light traveling along the optical axis L2 of the light receiving optical system 120 toward the light receiving element 126. The mask 130 of the first embodiment is disposed at a conjugate position with respect to the ring lens 125 or in the vicinity of the ring lens 125.

[0061] (Fixation Target Presenting Optical System) The fixation target presenting optical system 150 presents a fixation target to the subject's eye E, causing the subject's eye E to fixate. The fixation target presenting optical system 150 may also be used to apply fogging and accommodative load to the subject's eye E. The fixation target presenting optical system 150 includes a fixation light source 151, a fixation target plate 155, lenses 156 and 157, and an objective lens 505. The fixation light source 151 is disposed on the optical axis L4 of the fixation target presenting optical system 150. The fixation target plate 155 is disposed at a position conjugate with the fundus. A fixation light beam from the fixation light source 151 passes through the fixation target plate 155, lenses 156 and 157, then passes through the half mirror 502, is reflected by the half mirror 501, becomes coaxial with the optical axis L1, and further passes through the objective lens 505 to reach the fundus.

[0062] (Brightness Change Detection Optical System) The brightness change detection optical system 200 detects a change in brightness of light from the subject's eye E (e.g., light reflected by the subject's eye E from the light irradiated by the irradiation optical system 400). The change in brightness of light from the subject's eye E detected by the brightness change detection optical system 200 is used, for example, for relative alignment of the examination axis LA with respect to the subject's eye E, tracking of the examination axis LA relative to the movement of the subject's eye E, detection of tissues of the subject's eye E (e.g., the pupil or the posterior surface of the cornea), and acquisition of the state of specific tissues of the subject's eye E (e.g., the opacity state of the crystalline lens). The brightness change detection optical system 200 includes an event-based sensor 20, a lens 202, and an objective lens 505. The event-based sensor 20 of the first embodiment is disposed at a pupil conjugate position. Details of the event-based sensor 20 will be described later.

[0063] The luminance change detection optical system 200 is further equipped with a two-dimensional imaging element 204 and a lens 205. The two-dimensional imaging element 204 and the lens 205 are located on an optical axis branched by a half mirror from the optical axis L3 of the luminance change detection optical system 200. The two-dimensional imaging element 204 images the subject's eye E (the anterior segment of the subject's eye E in the first embodiment). The imaging range of the subject's eye E by the two-dimensional imaging element 204 overlaps with the range in which luminance changes are detected by the event-based sensor 20. More specifically, in the first embodiment, the imaging range of the subject's eye E by the two-dimensional imaging element 204 coincides with the range in which luminance changes are detected by the event-based sensor 20. Therefore, the positional relationship between two-dimensional information detected by the event-based sensor 20 (e.g., information on the distribution of light reflection characteristics in the subject's eye E) and the position of the subject's eye E imaged by the two-dimensional imaging element 204 is uniquely determined. Therefore, the control unit 50 can, for example, overlap information detected by the event-based sensor 20 (e.g., a brightness change distribution image described later) with the image of the subject's eye E captured by the two-dimensional imaging element 204 while aligning the position.

[0064] (Irradiation Optical System) The irradiation optical system 400 irradiates irradiation light onto the subject's eye E. The irradiation optical system 400 includes an infinity light irradiating optical system 401 and a finite light irradiating optical system 402.

[0065] The infinity light emitting optical system 401 emits collimated infinite light beams toward the cornea of ​​the subject's eye E from the front side facing the subject's eye E. The infinity light emitting optical system 401 includes a plurality of point light sources 410 that emit infinity light. The plurality of point light sources 410 are arranged symmetrically in the vertical and horizontal directions with respect to the examination axis LA. As an example, in the first embodiment, two point light sources 410 are provided on each side. This allows four infinity point-like indices (bright spots) to be projected onto the cornea. Note that the number of infinity point-like indices projected onto the cornea by the infinity light emitting optical system 401 is not limited to four, as long as it is three or more. Furthermore, the shape of the infinity indices projected onto the cornea by the infinity light emitting optical system 401 is not limited to a point shape, and may include a linear indices or the like. Note that the ophthalmic apparatus 1 can also easily measure the corneal shape using the indices projected onto the cornea by the infinity light emitting optical system 401.

[0066] The finite light irradiating optical system 402 irradiates finitely distant irradiation light, which is a diverging light beam, toward the cornea of ​​the test eye E from the front side facing the test eye E. The finite light irradiating optical system 402 includes a plurality of point light sources 420 that irradiate finitely distant light. The plurality of point light sources 420 are arranged symmetrically above and below the examination axis LA. As an example, in the first embodiment, point light sources 420 are provided above, below, to the right, and below the examination axis LA. As a result, four finitely distant point-like indices (bright spots) are projected onto the cornea. Note that the number of finitely distant point-like indices projected onto the cornea by the finite light irradiating optical system 402 is not limited to four. Furthermore, the shape of the finitely distant indices projected onto the cornea by the finite light irradiating optical system 402 is not limited to a point shape, and may include a linear (e.g., ring-shaped) indices.

[0067] The control unit 50 of the ophthalmologic apparatus 1 acquires, as analytical information, information on the distribution of reflection positions on the cornea of ​​the subject's eye E where the irradiated light is reflected in the direction received by the event-based sensor 20 (i.e., the distribution of indices (bright spots in the first embodiment) formed on the cornea by the irradiated light), based on the luminance change detected by the event-based sensor 20. The control unit 50 performs alignment in the X, Y, and Z directions of the optometry unit 12 (more specifically, the examination axis LA extending from the optometry unit 12 toward the subject's eye E) with respect to the cornea of ​​the subject's eye E, based on the distribution of reflection positions of the irradiated light. For example, the control unit 50 calculates the center of the reflection positions (four reflection positions in the first embodiment) of the finitely distant irradiation light irradiated by the finitely distant light irradiating optical system 402 as a reference position predicted to be the position of the corneal apex in directions intersecting the optometry unit 12 (X and Y directions in the first embodiment), and aligns the position of the examination axis LA (e.g., the center position of the light receiving area of ​​the event-based sensor 20) with the calculated reference position, thereby performing alignment in the X and Y directions. Furthermore, the control unit 50 can perform alignment in the Z direction of the optometry unit 12 with respect to the eye E based on the relative positional relationship between the reflection position of the finitely distant irradiation light irradiated by the finitely distant light irradiating optical system 402 and the reflection position of the infinitely distant irradiation light irradiated by the infinitely distant light irradiating optical system 401. When the distance in the Z direction between the eye E and the optometry unit 12 changes, the reflection position of the infinitely distant irradiation light on the cornea remains almost unchanged, but the reflection position of the finitely distant irradiation light changes. Therefore, by utilizing the relative positional relationship between the reflection position of the irradiated light at a finite distance and the reflection position of the irradiated light at an infinite distance, alignment in the Z direction can be performed appropriately.

[0068] (Diopter Correction Unit) The ophthalmologic apparatus 1 of the first embodiment includes a diopter correction unit. The diopter correction unit includes a drive unit 160 and a drive unit 161. The drive unit 160 can integrally move the measurement light source 111, the ring lens 125, and the light receiving element 126 in the measurement optical system 100, and the fixation light source 151 and the fixation target plate 155 in the fixation target presenting optical system 150 along the direction of the examination axis LA. The drive unit 161 moves the drive unit 160. For example, by moving the drive unit 160 according to the ocular refractive power of the subject's eye E (i.e., the diopter of the subject's eye), the presentation distance of the fixation target plate 155 relative to the subject's eye E (i.e., the presentation position of the fixation target) can be changed. The ring lens 125 and the light receiving element 126 of the light receiving optical system 120 are moved together so that the light receiving element 126 is near a conjugate position with respect to the fundus of the subject's eye E, and the imaging state (focus state) of the ring image received by the light receiving element 126 is adjusted according to the diopter of the subject's eye E.

[0069] (Control System) The control unit 50 includes a CPU (processor), RAM, and ROM. The CPU performs various controls on the ophthalmic apparatus 1. The RAM temporarily stores various pieces of information. The ROM stores various programs executed by the CPU. The control unit 50 may be configured with multiple processors. The control unit 50 is electrically connected to the relative position movement unit 13 (see FIG. 1 ), the monitor 16, the operation unit 17, a nonvolatile memory 55 (hereinafter referred to as memory 55), the light sources of the optometry unit 12, the light receiving elements (including the event-based sensor 20), and the drive units. The memory 55 is a non-transitory storage medium that can retain its contents even when the power supply is interrupted. For example, the memory 55 may be a hard disk drive, a flash ROM, a USB memory, or the like. An ophthalmic apparatus control program that controls the ophthalmic apparatus 1 may be stored in the memory 55.

[0070] (Event-Based Sensor) The event-based sensor 20 used in the ophthalmologic apparatus 1 of this embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic diagram of the event-based sensor 20 and an enlarged view of one pixel 21 viewed from the light-receiving area side. The event-based sensor 20 detects changes over time in the luminance of light incident on each pixel 21, and outputs information about the pixel 21 whose luminance has changed asynchronously with the other pixels 21.

[0071] As shown in FIG. 3 , in the event-based sensor 20, multiple pixels 21 are arranged (in a grid pattern in this embodiment) within a two-dimensional region extending in a direction intersecting the optical axis of the received light. Each pixel 21 includes a photodiode 23, a voltage conversion circuit 24, an asynchronous difference detection circuit 25, and a comparator 26. When the photodiode 23 receives light, it generates a current corresponding to the luminance of the received light. The voltage conversion circuit 24 converts the current generated by the photodiode 23 into a voltage. The asynchronous difference detection circuit 25 detects the difference between the voltage converted by the voltage conversion circuit 24 and a reference voltage asynchronously with respect to the other pixels 21. The comparator 26 outputs positive / negative information (event information) when the voltage difference detected by the asynchronous difference detection circuit 25 exceeds a positive threshold or a negative threshold. Specifically, when the voltage difference detected by the asynchronous difference detection circuit 25 exceeds the positive threshold, the comparator 26 outputs positive event information indicating that an "increasing (positive)" luminance change has occurred. Furthermore, when the voltage difference detected by the asynchronous difference detection circuit 25 exceeds a negative threshold, the comparator 26 outputs negative event information indicating that a "decreasing (negative)" luminance change has occurred.

[0072] When a positive or negative luminance change (event) occurs, the reference voltage is reset so that the luminance level at that time becomes the reference, and a positive (bright change) threshold and a negative (dark change) threshold are set based on the reference voltage. Each pixel 21 outputs, along with the positive / negative information, position information indicating the position coordinates of the pixel 21 where the luminance change exceeding the threshold occurred and time information indicating the time (or timing) when the luminance change exceeding the threshold occurred.

[0073] As described above, the event-based sensor 20 detects and outputs not the magnitude of the luminance of the light received by each pixel 21, but rather a change in the luminance of the light received by each pixel 21 that exceeds a threshold. Each pixel 21 operates independently, and immediately outputs information when it detects a change in the luminance of the received light that exceeds a threshold. As a result, changes in luminance that exceed the threshold are detected and output at ultra-high speed. Furthermore, the dynamic range of the event-based sensor 20 is wider than that of conventionally used two-dimensional imaging elements.

[0074] 4 and 5 , the first examination process executed by the ophthalmic apparatus 1 of the first embodiment will be described. In the first examination process, the distribution of reflection positions of irradiated light on the cornea (the distribution of indices projected on the cornea) is acquired as analysis information based on information output by the event-based sensor 20. Based on the acquired information on the distribution of reflection positions, a relative position adjustment (alignment) of the optometry unit 12 with respect to the subject's eye E is performed. The first examination process is executed by the control unit 50 of the ophthalmic apparatus 1 in accordance with an ophthalmic apparatus control program stored in a storage device (such as the memory 55).

[0075] 4 , the control unit 50 sets the threshold value for each pixel 21 of the event-based sensor 20 to detect changes in light luminance to a threshold value corresponding to the target for which distribution information on the reflectance characteristics of light is to be acquired (in the first testing process, the distribution of reflection positions of irradiated light on the cornea) (S1). By increasing the threshold value, information on the distribution of reflectance characteristics is acquired for areas where the changes in luminance of light received by the pixel 21 are large. On the other hand, by decreasing the threshold value, information on the distribution of reflectance characteristics is acquired for areas where the changes in luminance of light are small. Therefore, by changing the threshold value, the control unit 50 can appropriately change the target for which information on the distribution of reflectance characteristics is to be acquired.

[0076] The amount of reflection of the irradiated light by the cornea tends to be greater than the amount of reflection of the irradiated light by a part of the subject's eye other than the cornea (for example, the iris, etc.). Therefore, in S1, the threshold value set when the target for acquiring distribution information of reflection characteristics is the cornea is greater than the threshold value set when the target is a part of the subject's eye other than the cornea (for example, the threshold value set in S21 (see FIG. 6) described later).

[0077] Furthermore, when the brightness of the environment in which the ophthalmic apparatus 1 is installed changes, the threshold value of the event-based sensor 20 suitable for acquiring the analytical information also changes. Therefore, the control unit 50 may acquire information about the brightness of the environment in which the ophthalmic apparatus 1 is installed from a sensor or the like and set the threshold value based on the acquired brightness information. In this case, the accuracy of acquiring the analytical information is likely to be improved regardless of changes in the brightness of the installation environment. Furthermore, the control unit 50 may improve the accuracy of acquiring the analytical information by changing the threshold value according to individual differences in the subject's eye E.

[0078] The control unit 50 executes flashing irradiation, flashing the irradiation light irradiated from the irradiation optical system 400 onto the subject's eye E (S2). The event-based sensor 20 outputs changes in the luminance of the received light, but if the luminance of the received light does not change, no information is output even if a difference in luminance occurs within the light-receiving area. In contrast, when the irradiation light is flashed, the luminance of the received light changes between when the light is on and when it is off in areas where the irradiation light is reflected toward the event-based sensor 20. On the other hand, in areas where the irradiation light is not reflected toward the event-based sensor 20, the luminance of the received light naturally does not change even if the irradiation light is flashed. In other words, by flashing the irradiation light, the distribution of the light reflection characteristics of the subject's eye (e.g., characteristics of whether or not light is reflected toward the event-based sensor 20) is reflected in the output result from the event-based sensor 20.

[0079] In S2 of the first embodiment, the control unit 50 blinks at least two types of light sources included in the irradiation optical system 400 at different cycles. Specifically, in S2 of the first embodiment, the control unit 50 blinks the light sources included in the infinite light irradiation optical system 401 and the finite light irradiation optical system 402 at different cycles. As a result, information on the distribution of light reflection characteristics varies for each type of light source depending on the blinking cycle of each of the multiple types of light sources. Therefore, the distribution of light reflection characteristics (e.g., the distribution of reflection positions, which will be described later) can be distinguished for each type of light source that emitted the reflected light. In other words, in the first embodiment, the distribution of reflection characteristics due to the infinitely distant irradiation light irradiated by the infinite light irradiation optical system 401 and the distribution of reflection characteristics due to the finitely distant irradiation light irradiated by the finite light irradiation optical system 402 can be appropriately distinguished.

[0080] In addition, the rate at which the light is switched on and off (the number of times the light is switched on and off per unit time) during flashing illumination is set to a rate greater than the frame rate (typically 100 fps) achievable with two-dimensional imaging elements used in conventional ophthalmic devices. Therefore, changes in luminance can be detected with higher time resolution than in conventional ophthalmic devices that detect corneal landmarks using two-dimensional imaging elements such as general CMOS image sensors. Furthermore, a specific method for changing the flashing cycle of each of the multiple types of light sources can be selected as appropriate. For example, the timing at which the flashing cycle is repeated (the timing at which the light is turned on and off) may be changed between the multiple types of light sources. Furthermore, the length of the flashing cycle may be changed between the multiple types of light sources.

[0081] The control unit 50 starts capturing an image (a moving image in the first embodiment) of the subject's eye E using the two-dimensional image capturing element 204 (S3). As described above, at least a portion of the image capturing area of ​​the two-dimensional image capturing element 204 overlaps with the area in which the event-based sensor 20 detects a change in the luminance of light.

[0082] Next, the control unit 50 acquires analytical information indicating at least one of the position, displacement, shape, and tissue state of the subject's eye E (in the first examination process, distribution information of light reflection characteristics indicating the position and shape of the subject's eye E) based on the information output by the event-based sensor 20 (S5 to S7). By utilizing the characteristics of the event-based sensor 20, which outputs changes in luminance rather than light magnitude information, the control unit 50 can acquire highly accurate analytical information (e.g., analytical information with a substantially constant luminance and suppressing the influence of unnecessary ambient light) with high temporal resolution. Furthermore, the dynamic range of the event-based sensor 20 is wider than that of conventionally used two-dimensional imaging elements, making it less susceptible to influences such as insufficient light quantity and contrast.

[0083] In the first test process, the control unit 50 acquires information (the above-described positive / negative information (event information), position information, and time information) output by the event-based sensor 20 at a timing corresponding to the rate at which the flashing irradiation by the irradiation optical system 400 is switched on and off (S5). Next, the control unit 50 acquires distribution information of the reflection characteristics of the subject's eye E at the same rate as S5 based on the information acquired in S5 (S6). Therefore, processing of the information output by the event-based sensor 20 is repeatedly executed at an appropriate timing corresponding to the rate at which the irradiation light is switched on and off. Therefore, information regarding the distribution of the reflection characteristics of light is acquired with high time resolution. Furthermore, even when unnecessary disturbance light is flashing, if the flashing rate of the disturbance light and the flashing rate of the irradiation light differ, the output information from the event-based sensor 20 is processed according to the flashing rate of the irradiation light, making it difficult for the influence of the disturbance light to be reflected in the analysis information (in the first test process, the distribution information of the reflection characteristics). In the first inspection process, the rate at which the information output from event-based sensor 20 is processed is the same as the rate at which the irradiated light is switched on and off. In this case, the influence of unnecessary ambient light is more easily eliminated when obtaining information about the distribution of light reflectance characteristics.

[0084] As described above, in the first embodiment, the blinking period of the infinitely distant light irradiated by the infinitely distant light irradiating optical system 401 is different from the blinking period of the finitely distant light irradiated by the finitely distant light irradiating optical system 402. S5 and S6 in the first embodiment are executed at a timing corresponding to the switching rate between blinking and turning off of the infinitely distant light, and at a timing corresponding to the switching rate between blinking and turning off of the finitely distant light, respectively. As a result, the distribution of reflectance characteristics due to the infinitely distant light and the distribution of reflectance characteristics due to the finitely distant light can be appropriately distinguished.

[0085] In S6 of the first examination process, the control unit 50 acquires, as analytical information, information on the distribution of reflection positions on the cornea of ​​the subject's eye E where the illumination light emitted by the illumination optical system 400 is reflected toward the event-based sensor 20. The distribution of reflection positions on the cornea of ​​the subject's eye E where the illumination light is reflected toward the event-based sensor 20 approximates or matches the distribution of corneal index positions that would appear in a captured image if the event-based sensor 20 were replaced with a two-dimensional imaging element. Therefore, by acquiring analytical information on the distribution of reflection positions on the cornea based on the information output by the event-based sensor 20, the ophthalmologic apparatus 1 can appropriately perform control similar to conventional control that uses the distribution of corneal index positions (e.g., alignment control, which will be described later in S29).

[0086] The control unit 50 processes the output information from the event-based sensor 20 acquired in S5 to generate a luminance change distribution image (S7) that shows the two-dimensional distribution of luminance changes in the light received by the event-based sensor 20. The luminance change distribution image allows the two-dimensional distribution of luminance changes in the subject's eye E (the cornea in the first testing process) to be properly understood. Note that in S7 of this embodiment, the control unit 50 generates the luminance change distribution image by visualizing the distribution information of the light reflection characteristics acquired in S6.

[0087] The control unit 50 superimposes the light reflection characteristic distribution acquired in S6 (in this embodiment, the brightness change distribution image generated in S7) on the image of the subject's eye E captured by the two-dimensional imaging element 204 and displays the superimposed image on a display unit (e.g., the monitor 16) (S8). This allows the examiner to properly grasp the reflection characteristic distribution acquired based on the output information of the event-based sensor 20 on the captured image of the subject's eye E. For example, it also becomes easier to visually grasp misalignment of the reflection characteristic distribution. Therefore, for example, the examiner can properly perform alignment by manually adjusting the relative position of the optometry unit 12 with respect to the subject's eye E while checking the displayed superimposed image. Furthermore, when processing an image of the subject's eye on which the reflection characteristic distribution is superimposed, processing results can be more easily obtained with high accuracy.

[0088] 5 shows an example of a superimposed image of the luminance change distribution image generated in the first examination process. As shown in Fig. 5, in the superimposed image generated in the first examination process, the distribution of the reflection positions of the irradiated light on the cornea is superimposed on the photographed image of the anterior segment of the eye E to be examined.

[0089] The control unit 50 automatically adjusts (aligns) the relative position of the optometry unit 12 with respect to the subject's eye E (S9) by driving the relative position moving unit 13 (see FIG. 1) based on the distribution of reflection positions on the cornea acquired in S6 and S7. As a result, alignment with high time resolution is performed while the influence of unnecessary ambient light is suppressed.

[0090] As described above, in steps S5 to S7 of this embodiment, the distribution of reflection characteristics due to light irradiated at infinity and the distribution of reflection characteristics due to light irradiated at a finite distance are appropriately distinguished. Therefore, in step S9, the control unit 50 can perform alignment with high precision by clearly distinguishing between the reflection positions of light irradiated at a finite distance and the reflection positions of light irradiated at infinity.

[0091] Next, the control unit 50 determines whether a trigger to start the examination of the subject's eye E (for example, an instruction to start the examination from the user, an alignment completion signal, etc.) has been input (S11). If a trigger has not been input (S11: NO), the process returns to S5, and the processes of S5 to S11 are repeated to continue the alignment. When a trigger to start the examination is input (S11), the control unit 50 performs an examination of the subject's eye E using the optometry unit 12 (S12), and the first examination process ends.

[0092] (Second Examination Process) The second examination process executed by the ophthalmic apparatus 1 of the first embodiment will be described with reference to Figures 6 and 7. In the second examination process, the position of the pupil located at the center of the iris is detected based on information output by the event-based sensor 20. Based on the detected pupil position, a relative position adjustment (alignment) of the optometry unit 12 with respect to the subject's eye E is performed. The second examination process is executed by the control unit 50 of the ophthalmic apparatus 1 in accordance with an ophthalmic apparatus control program stored in a storage device (such as the memory 55). Note that in the following description, explanations of parts that can employ techniques similar to those described in the first examination process will be omitted or simplified.

[0093] 6, the control unit 50 sets the threshold value for detecting a change in light luminance by each pixel 21 of the event-based sensor 20 to a threshold value corresponding to the target for which distribution information on the reflectance characteristics of light is to be obtained (in the second test process, the distribution of the reflectance characteristics of irradiated light on the iris) (S21). As described above, the threshold value set in S21 is smaller than the threshold value set in S1 of the first test process (see FIG. 4).

[0094] The control unit 50 executes an increasing / decreasing illumination process, repeatedly increasing / decreasing the intensity of the illumination light irradiated onto the subject's eye E from the illumination optical system 400 over time (S22). When the intensity of the illumination light is linearly increased / decreased over time, the luminance of the received light changes in response to the increase / decrease in the intensity of the illumination light at the portion where the illumination light is reflected toward the event-based sensor 20. On the other hand, at the portion where the illumination light is not reflected toward the event-based sensor 20, the luminance of the received light naturally does not change even if the intensity of the illumination light is increased / decreased. In other words, by increasing / decreasing the intensity of the illumination light, the distribution of the light reflection characteristics of the subject's eye E (in the first embodiment, the characteristics of the degree to which light is reflected toward the event-based sensor) is reflected in the output result from the event-based sensor 20. Therefore, by increasing / decreasing the intensity of the illumination light, the ophthalmic apparatus 1 can appropriately acquire analytical information regarding the distribution of the light reflection characteristics of the subject's eye E based on the information output by the event-based sensor 20. Furthermore, by acquiring analytical information based on the output of event-based sensor 20, analytical information is acquired with the influence of unnecessary ambient light suppressed, unlike when a two-dimensional imaging element is used. Furthermore, although the intensity of the irradiated light increases or decreases, the irradiated light continues to be emitted, so that control unit 50 can continuously acquire analytical information with high time resolution.

[0095] In S22 of this embodiment, the control unit 50 sets different timings for increasing and decreasing the intensity of the illumination light from each of the at least two types of light sources included in the illumination optical system 400. Specifically, in S22 of this embodiment, the control unit 50 increases and decreases the illumination light intensity of the light sources included in the infinite light illumination optical system 401 and the finite light illumination optical system 402 at different timings. As a result, the positive / negative information output by the event-based sensor 20 changes for each light source depending on the timing for increasing and decreasing the light intensity of each of the multiple types of light sources. Therefore, the acquired information on the distribution of the light reflectance characteristics changes for each light source. Therefore, the distribution of the light reflectance characteristics is distinguished for each light source that emits the reflected light. In other words, in this embodiment, the distribution of the reflectance characteristics resulting from the infinitely distant illumination light illuminated by the infinite light illumination optical system 401 and the distribution of the finitely distant illumination light illuminated by the finite light illumination optical system 402 are appropriately distinguished.

[0096] Note that the specific method for changing the timing for increasing and decreasing the light intensity of each of the multiple types of light sources can be selected as appropriate. In this embodiment, the timing for increasing and decreasing the light intensity of each of the two types of light sources (a light source emitting light at an infinite distance and a light source emitting light at a finite distance) is set so that the period for increasing the light intensity of one type of light source coincides with the period for decreasing the light intensity of the other type of light source. Therefore, if the position where light emitted by one type of light source is reflected toward the event-based sensor 20 does not overlap with the position where light emitted by the other type of light source is reflected toward the event-based sensor 20, the positive / negative information of one type of light source and the positive / negative information of the other type of light source will be reversed. This makes it easier to more accurately distinguish the distribution of light reflection characteristics according to the type of light source.

[0097] The control unit 50 starts capturing an image (a moving image in this embodiment) of the subject's eye E using the two-dimensional imaging element 204 (S23). Next, the control unit 50 acquires analytical information indicating at least one of the position, displacement, shape, and tissue state of the subject's eye E based on the information output by the event-based sensor 20 (S25, S26). In particular, the control unit 50 acquires the distribution information of the reflection characteristics of the subject's eye E as analytical information based on the information output by the event-based sensor 20 (S25).

[0098] The control unit 50 processes the output information from the event-based sensor 20 to generate a luminance change distribution image that shows the two-dimensional distribution of luminance changes in the light received by the event-based sensor 20 (S26). The luminance change distribution image allows the two-dimensional distribution of luminance changes in the subject's eye E (the iris in the second examination process) to be properly understood. Note that in S26 of this embodiment, the control unit 50 generates the luminance change distribution image by visualizing the distribution information of the light reflection characteristics acquired in S25.

[0099] The control unit 50 superimposes the distribution of light reflection characteristics acquired in S25 (in this embodiment, the brightness change distribution image generated in S26) on the image of the subject's eye E captured by the two-dimensional imaging element 204 and displays the superimposed image on the display unit (e.g., the monitor 16) (S27). This allows the examiner to properly grasp the distribution of reflection characteristics acquired based on the output information of the event-based sensor 20 on the captured image of the subject's eye E. Therefore, for example, the examiner can properly perform alignment by manually adjusting the relative position of the optometry unit 12 with respect to the subject's eye E while checking the displayed superimposed image. Furthermore, when processing an image of the subject's eye on which the distribution of reflection characteristics is superimposed, results can be more easily obtained with higher accuracy.

[0100] Fig. 7 shows an example of a superimposed image of the luminance change distribution image generated in the second examination process. As shown in Fig. 7, in the superimposed image generated in the second examination process, the distribution of the reflection positions of the irradiated light on the iris is superimposed on the photographed image of the anterior segment of the subject's eye E. Furthermore, in the superimposed image shown in Fig. 7, the position of the pupil in the center of the iris is clearly shown.

[0101] The control unit 50 detects the position of the pupil in the center of the iris based on the distribution information of the reflection characteristics acquired in S25 or the luminance change distribution image generated in S26 (S28). The detection of the pupil position can be performed using, for example, known image processing (edge ​​detection, etc.). The control unit 50 automatically adjusts (aligns) the position of the optometry unit 12 relative to the pupil of the subject's eye E by driving the relative position moving unit 13 (see FIG. 1) based on the information on the pupil position detected in S28 (S29). As a result, alignment with high time resolution is performed while the effects of unnecessary ambient light are suppressed.

[0102] Next, the control unit 50 determines whether a trigger to start the examination of the subject's eye E has been input (S31). If a trigger has not been input (S31: NO), the process returns to S25, and the processes of S25 to S31 are repeated to continue alignment. When a trigger to start the examination is input (S31), the control unit 50 performs an examination of the subject's eye E using the optometry unit 12 (S32), and the second examination process ends.

[0103] 8 and 9, an ophthalmic apparatus 60 according to a second embodiment will be described. The ophthalmic apparatus 60 according to the second embodiment can acquire a tomographic image of the fundus by processing an OCT signal acquired using biological tissue of the fundus of an eye E as a subject.

[0104] 1, the schematic configuration of an ophthalmic apparatus 60 according to the second embodiment will be described. The ophthalmic apparatus 60 according to the second embodiment includes an OCT section (ophthalmic examination unit) 70 and a control section 90. The OCT section 70 includes an OCT light source 71, a coupler (light splitter) 72, a measurement optical system 73, a reference optical system 80, a light receiving element 82, an irradiation optical system 83, and an event-based sensor 84.

[0105] The OCT light source 71 emits light (OCT light) for acquiring an OCT signal. The coupler 72 splits the OCT light emitted from the OCT light source 71 into measurement light and reference light. The coupler 72 of this embodiment combines the measurement light reflected by the subject's biological tissue (in this embodiment, the fundus tissue of the subject's eye E) with the reference light generated by the reference optical system 80 to cause interference. That is, the coupler 72 of this embodiment serves both as a branching optical element that branches the OCT light into measurement light and reference light, and as a combining optical element that combines the reflected light of the measurement light with the reference light. It is also possible to change the configuration of at least one of the branching optical element and the combining optical element. For example, an element other than a coupler (e.g., a circulator, a beam splitter, etc.) may be used.

[0106] The measurement optical system 73 guides the measurement light split by the coupler 72 to the subject and returns the measurement light reflected by the subject to the coupler 72. The measurement optical system 73 includes an examination position moving unit 74 and a focus adjusting unit 77. The examination position moving unit 74 moves the examination position of the OCT unit (ophthalmology unit) 70. As an example, the examination position moving unit 74 in this embodiment is an irradiation position moving unit that moves the irradiation position of the light (OCT measurement light) used for examination. More specifically, the examination position moving unit 74 in this embodiment is a scanning unit (optical scanner) that is driven by a driving unit 75 to scan (deflect) the measurement light in a two-dimensional direction intersecting the optical axis of the measurement light. In this embodiment, two galvanometer mirrors capable of deflecting the measurement light in different directions are used as the examination position moving unit 74. However, another device that deflects light (e.g., at least one of a polygon mirror, a resonant scanner, an acousto-optical element, etc.) may also be used as the examination position moving unit 74. The focus adjustment unit 77 adjusts the focus of the measurement light by moving an optical member (for example, a lens) included in the irradiation optical system 76 in a direction along the optical axis of the measurement light.

[0107] The reference optical system 80 generates reference light and returns it to the coupler 72. The reference optical system 80 of this embodiment generates the reference light by reflecting the reference light split by the coupler 72 using a reflective optical system (e.g., a reference mirror). However, the configuration of the reference optical system 80 can also be changed. For example, the reference optical system 80 may transmit the light incident from the coupler 72 without reflecting it and return it to the coupler 72. The reference optical system 80 includes an optical path length difference adjustment unit 81 that changes the optical path length difference between the measurement light and the reference light. In this embodiment, the optical path length difference is changed by moving the reference mirror in the optical axis direction. Note that the configuration for changing the optical path length difference may be provided in the optical path of the measurement optical system 73.

[0108] The light-receiving element 82 detects an interference signal by receiving interference light between the measurement light and the reference light generated by the coupler 72. In this embodiment, the principle of Fourier-domain OCT is adopted. In Fourier-domain OCT, the spectral intensity of the interference light (spectral interference signal) is detected by the light-receiving element 82, and a complex OCT signal is acquired by Fourier transforming the spectral intensity data. Examples of Fourier-domain OCT that can be adopted include spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). It is also possible to adopt, for example, time-domain OCT (TD-OCT).

[0109] Furthermore, in this embodiment, the measurement light spot is scanned within a two-dimensional measurement region by the inspection position moving unit 74, thereby acquiring three-dimensional OCT data (e.g., a three-dimensional tomographic image). However, the principle of acquiring three-dimensional OCT data can be changed. For example, three-dimensional OCT data may be acquired using the principle of line-field OCT (hereinafter referred to as "LF-OCT"). In LF-OCT, measurement light is simultaneously irradiated onto an irradiation line extending in a one-dimensional direction in tissue, and the reflected light of the measurement light and the interference light of the reference light are received by a one-dimensional light-receiving element (e.g., a line sensor) or a two-dimensional light-receiving element. The measurement light is scanned within the two-dimensional measurement region in a direction intersecting the irradiation line, thereby acquiring three-dimensional OCT data.

[0110] The irradiation optical system 83 irradiates the subject's eye E with irradiation light. The event-based sensor 84 detects changes in the luminance of light incident on each pixel over time and outputs information about pixels whose luminance has changed asynchronously with that of other pixels. The event-based sensor 84 of the second embodiment can be a sensor similar to the event-based sensor 20 of the first embodiment (see FIG. 3 ). Therefore, a detailed description of the event-based sensor 84 will be omitted in the second embodiment. Note that the irradiation optical system 83 of the second embodiment constantly irradiates irradiation light with a constant intensity. In this case, even if the irradiation light emitted from the irradiation optical system 83 is reflected by an optical element (e.g., a lens) in the optical path and the reflected light enters the event-based sensor 84, the intensity of the reflected light is constant, so the reflection of the irradiation light by the optical element does not affect the detection of changes in luminance by the event-based sensor 84. Therefore, in the ophthalmic apparatus 60 of the second embodiment, the light source of the irradiation optical system 83 is provided inside the housing. The irradiation optical system 83 irradiates the subject's eye E with irradiation light via the optical element.

[0111] The control unit 90 includes a CPU (processor), RAM, and ROM. The CPU performs various controls in the ophthalmic apparatus 60. The RAM temporarily stores various types of information. The ROM stores various programs executed by the CPU. An ophthalmic apparatus control program that controls the ophthalmic apparatus 60 may be stored in the ROM, etc.

[0112] (Tracking Process) The tracking process executed by the ophthalmic apparatus 60 of the second embodiment will be described with reference to Fig. 9. In the tracking process, tracking is performed to cause the examination position of the OCT section (ophthalmological unit) 70 to follow the displacement of a specific part of the subject's eye E (the fundus in the second embodiment) based on information output by the event-based sensor 84. The tracking process is executed by the control section 90 of the ophthalmic apparatus 60 in accordance with an ophthalmic apparatus control program stored in the storage device.

[0113] First, the control unit 90 sets a threshold value for detecting a change in light luminance by each pixel of the event-based sensor 84 to a threshold value corresponding to the target (the fundus in the second embodiment) from which analysis information (displacement information indicating the displacement of the fundus in the present embodiment) is to be acquired (S41). The control unit 90 constantly irradiates the fundus of the subject's eye E with irradiation light of a constant intensity from the irradiation optical system 83 (S42).

[0114] Next, the control unit 90 acquires, as analysis information, displacement information indicating the displacement of a specific site (fundus) based on the information output by the event-based sensor 84 (S43). Specifically, the control unit 90 acquires displacement information indicating the displacement of the fundus of the subject's eye E based on the position information of pixels from the event-based sensor 84 that output positive / negative event information (positive event information or negative event information). As described above, the event-based sensor 84 detects changes in luminance with higher temporal resolution than conventional two-dimensional imaging devices. Therefore, the control unit 90 can grasp the displacement of the fundus (e.g., the displacement direction and displacement amount) with high temporal resolution by acquiring displacement information (e.g., vector information) indicating the displacement of the fundus based on the positions of the pixels that output positive / negative event information. The control unit 90 drives the examination position moving unit 74 based on the displacement information acquired in S43, thereby causing the examination position to track the displacement of the fundus (S44). The processes of S43 to S45 are repeated until a trigger to end tracking is input (S45: NO). When the termination trigger is input (S45: YES), the tracking process ends.

[0115] <Modifications> The techniques disclosed in the above embodiments are merely examples. Therefore, the techniques exemplified in the above embodiments can be modified. First, it is possible to selectively adopt only some of the techniques exemplified in the above embodiments in the ophthalmic apparatus. Furthermore, in the first examination process, the ophthalmic apparatus 1 blinks the irradiation light emitted from the irradiation optical system 400 to acquire distribution information on the reflection positions of the irradiation light on the cornea. However, the ophthalmic apparatus 1 may increase or decrease the intensity of the irradiation light emitted from the irradiation optical system 400 over time to acquire distribution information on the reflection positions of the irradiation light on the cornea. Furthermore, in the second examination process, the intensity of the irradiation light emitted from the irradiation optical system 400 increases or decreases over time to acquire distribution information on the reflection characteristics of the irradiation light on the iris. However, the ophthalmic apparatus 1 may blink the irradiation light emitted from the irradiation optical system 400 to acquire distribution information on the reflection characteristics of the irradiation light on the iris.

[0116] In the second embodiment, an irradiation position moving unit that moves the irradiation position of light for examination is used as the examination position moving unit 74 that moves the examination position of the fundus by the OCT unit (ophthalmology unit) 70. However, a relative position moving unit that moves the relative position of the ophthalmology unit with respect to the subject's eye E may also be used as the examination position moving unit. Furthermore, it is also possible to employ the technology exemplified in the present disclosure to cause the examination position to follow the displacement of the anterior segment of the subject's eye E.

[0117] The ophthalmic apparatuses of the first and second embodiments each include one event-based sensor. However, the ophthalmic apparatus may include multiple event-based sensors. For example, in the first embodiment, an event-based sensor may be installed instead of the two-dimensional image sensor 204, and information on changes in light luminance in the same area of ​​the subject's eye may be acquired by each of the multiple event-based sensors. The use of multiple event-based sensors may also be selected as appropriate. For example, by setting different threshold values ​​for the pixels of the event-based sensors to detect changes in light luminance, even if there are multiple targets for which the distribution of reflectance characteristics is to be acquired, it is possible to simultaneously acquire the distributions of reflectance characteristics for the multiple targets.

[0118] As illustrated in the first examination process, when the target for acquiring distribution information on the reflectance characteristics of irradiated light is the cornea, the control unit of the ophthalmic device may set the threshold of the event-based sensor to a first threshold of a predetermined magnitude. On the other hand, when the target for acquiring distribution information on the reflectance characteristics includes not only the cornea but also other regions, the control unit may set a second threshold smaller than the first threshold. Here, the control unit may identify or separate distribution information on the reflectance characteristics of regions of the test eye other than the cornea by comparing the distribution information on the reflectance characteristics acquired when the second threshold is set with the distribution information on the reflectance characteristics acquired when the first threshold is set. This makes it easier to perform an appropriate examination of the test eye. Furthermore, a similar method may be used to identify or separate distribution information on the reflectance positions due to irradiated light at a finite distance from distribution information on the reflectance positions due to irradiated light at an infinite distance.

[0119] Furthermore, the control unit of the ophthalmologic apparatus can obtain analytical information indicating the state of the specific tissue (e.g., whether or not the specific tissue is opaque, or the degree of opacity in the specific tissue) by processing distribution information (which may be a luminance change distribution image including information on luminance changes in the light reflected by the specific tissue) of the reflection characteristics of light reflected by the specific tissue, which may be a tissue of the subject's eye that may be opaque (e.g., the crystalline lens). If no opacity is present, the intensity of the light reflected by the specific tissue is low, but the more opacity there is, the greater the intensity of the light reflected by the specific tissue. Therefore, by processing the distribution information of the reflection characteristics or the luminance change distribution image, the state of opacity in the specific tissue can be appropriately determined. Furthermore, the control unit can obtain analytical information, such as information on the location of opacity in the specific tissue, by processing the distribution information of the reflection characteristics or the luminance change distribution image.

[0120] The control unit of the ophthalmic apparatus may acquire distribution information of the reflectance characteristics of the anterior surface of the cornea by setting the threshold of the event-based sensor to a third threshold of a predetermined magnitude. The control unit may acquire distribution information of the reflectance characteristics of both the anterior and posterior surfaces of the cornea by setting a fourth threshold smaller than the third threshold. The control unit may acquire the position, shape, etc. of the posterior surface of the cornea by comparing the distribution information of the reflectance characteristics acquired when the fourth threshold is set with the distribution information of the reflectance characteristics acquired when the third threshold is set.

[0121] REFERENCE SIGNS LIST 1 Ophthalmic apparatus 12 Ophthalmological examination unit 13 Relative position moving unit 20 Event-based sensor 21 Pixel 50 Control unit 60 Ophthalmological apparatus 70 OCT unit (ophthalmological examination unit) 74 Examination position moving unit 83 Irradiation optical system 84 Event-based sensor 90 Control unit 200 Brightness change detection optical system 204 Two-dimensional imaging element 400 Irradiation optical system

Claims

1. An ophthalmic device for examining an eye to be examined, comprising: an illumination optical system that irradiates the eye to be examined with illumination light; a sensor that receives the light irradiated by the illumination optical system and reflected by the eye to be examined; and a control unit, wherein the sensor is an event-based sensor that detects and outputs changes in the brightness of the received light that exceed a threshold value for each pixel, and the control unit obtains analytical information indicating at least one of the position, displacement, shape, and tissue state of the eye to be examined based on the information output by the event-based sensor.

2. An ophthalmic device according to claim 1, wherein the irradiation optical system performs flashing irradiation by flashing the irradiation light irradiated onto the subject's eye while the analysis information is being acquired, and the control unit acquires, as the analysis information, information on the distribution of the light reflection characteristics of the subject's eye based on information output by the event-based sensor while the flashing irradiation is being performed by the irradiation optical system.

3. An ophthalmic device according to claim 2, characterized in that the control unit processes information output by the event-based sensor at a rate corresponding to the rate at which the flashing irradiation by the irradiation optical system is switched on and off, to obtain information on the distribution of the reflection characteristics of the light.

4. An ophthalmic device according to claim 2 or 3, wherein the irradiation optical system comprises a plurality of light sources that emit irradiation light, and the blinking periods of at least two of the light sources are different from each other.

5. An ophthalmic device according to claim 1, wherein the irradiation optical system performs increasing and decreasing irradiation, increasing and decreasing the intensity of the irradiation light irradiated onto the subject's eye over time while the analysis information is being acquired, and the control unit acquires, as the analysis information, information on the distribution of the light reflection characteristics of the subject's eye based on information output by the event-based sensor while the irradiation optical system is performing the increasing and decreasing irradiation.

6. An ophthalmic device according to claim 5, wherein the event-based sensor outputs positive / negative information for each pixel indicating whether the change in luminance that has occurred is an increase or a decrease, the irradiation optical system comprises a plurality of light sources that emit irradiation light, and the timing at which the intensity of the irradiation light of each of at least two of the light sources increases or decreases is different from each other.

7. An ophthalmic device according to any one of claims 2 to 6, wherein the irradiation optical system irradiates irradiation light onto the cornea of ​​the subject's eye, the event-based sensor is positioned so as to be able to receive reflected light reflected by the cornea of ​​the subject's eye, and the control unit acquires, as the analysis information, information on the distribution of reflection positions on the cornea of ​​the subject's eye where the irradiation light is reflected in a direction received by the event-based sensor.

8. An ophthalmic device according to any one of claims 2 to 7, further comprising a two-dimensional imaging element that captures at least an area of ​​the subject's eye that overlaps with an area in which a change in light luminance is detected by the event-based sensor, and wherein the control unit displays on a display unit the distribution of light reflection characteristics of the subject's eye, acquired based on output information from the event-based sensor, superimposed on the image of the subject's eye captured by the two-dimensional imaging element.

9. An ophthalmic device according to any one of claims 2 to 8, wherein the control unit changes the threshold value used by the pixels of the event-based sensor to detect changes in light luminance depending on the object for which information on the distribution of reflection characteristics is to be obtained.

10. An ophthalmic apparatus according to any one of claims 1 to 9, characterized in that it comprises a plurality of the event-based sensors.

11. An ophthalmic apparatus according to claim 1, further comprising an optometry unit that performs an examination on the subject's eye, and an examination position movement unit that moves the examination position of the optometry unit, wherein the event-based sensor outputs positive / negative information for each pixel that indicates whether a change in luminance that has occurred is an increase or a decrease, the irradiation optical system constantly irradiates the subject's eye with irradiation light of a constant intensity while acquiring the analysis information, and the control unit acquires, as the analysis information, displacement information that indicates a displacement of a specific part of the subject's eye based on the position of the pixel that output the positive / negative information, and drives the examination position movement unit based on the acquired displacement information, thereby causing the examination position to follow the displacement of the specific part.

12. An ophthalmic device according to any one of claims 1 to 11, wherein the event-based sensor has a plurality of pixels arranged in a two-dimensional area that intersects with the optical axis of the received light, and the control unit processes information output by each of the plurality of pixels to generate a brightness change distribution image that shows the two-dimensional distribution of changes in brightness of the received light.

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