# Patent

## Title
Ophthalmic apparatus, method for controlling ophthalmic apparatus, and storage medium

## Abstract

An ophthalmic apparatus comprising: an illumination optical system including a light source and configured to illuminate an eye to be examined; an imaging optical system including an image sensor and configured to image the eye illuminated by the illumination optical system; an optical member insertion/removal unit configured to insert/remove an optical member in/from at least one of optical paths in the illumination optical system and the imaging optical system; and a notification unit configured to notify an insertion/removal state of the optical member with respect to the optical path based on a signal output from the image sensor in synchronism with insertion/removal of the optical member in/from the optical path.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ophthalmic apparatus, a method for controlling the ophthalmic apparatus, and a storage medium.
2. Description of the Related Art
Recently, hospitals, doctor's offices, and the like widely use ophthalmic apparatuses. For example, as ophthalmic apparatuses which decide various conditions by using optical members in the apparatuses before imaging and measurement, ophthalmic apparatuses like those disclosed in Japanese Patent Laid-Open Nos. 2001-245848 and 2006-14904 have been known.
In the ophthalmic imaging apparatus disclosed in Japanese Patent Laid-Open No. 2001-245848, the diffusing plate inserted at a position in the optical path shared by the illumination optical system and the imaging optical system diffuses and scatters the light flux emitted by the fundus illumination unit, and the fundus image sensor provided in the imaging optical system images the scattered light. This literature discloses a technique of performing white balance adjustment by using the captured image.
The ocular refractive power measurement apparatus disclosed in Japanese Patent Laid-Open No. 2006-14904 has a reflecting member detachably placed at a fundus conjugate position in the optical path shared by the projection optical system and the light receiving optical system. This literature discloses a technique of reflecting the light flux projected from the measurement light source by using the reflecting member, and receiving the reflected light by using the light receiving element provided in the light receiving optical system, thereby acquiring correction data from changes in the reflected image due to changes in temperature.
However, the ophthalmic apparatus disclosed in Japanese Patent Laid-Open No. 2001-245848 or 2006-14904 does not detect the insertion/removal of the diffusing plate and reflecting member. For this reason, the apparatus cannot detect any failure of the insertion/removal of an optical member due to temporal deterioration. This may have adverse effects on ophthalmic imaging results.
SUMMARY OF THE INVENTION
In consideration of the above problem, the present invention provides a technique of finding a failure of the insertion/removal of an optical member due to temporal deterioration.
According to one aspect of the present invention, there is provided an ophthalmic apparatus comprising: an illumination optical system including a light source and configured to illuminate an eye to be examined; an imaging optical system including an image sensor and configured to image the eye illuminated by the illumination optical system; an optical member insertion/removal unit configured to insert/remove an optical member in/from at least one of optical paths in the illumination optical system and the imaging optical system; and a notification unit configured to notify an insertion/removal state of the optical member with respect to the optical path based on a signal output from the image sensor in synchronism with insertion/removal of the optical member in/from the optical path.
According to one aspect of the present invention, there is provided a method for controlling an ophthalmic apparatus, the method comprising the steps of: inserting/removing an optical member in/from at least one of optical paths in an illumination optical system including a light source and configured to illuminate an eye to be examined and an imaging optical system including an image sensor and configured to image the eye illuminated by the illumination optical system; and notifying of an insertion/removal state of the optical member with respect to the optical path based on a signal output from the image sensor in synchronism with insertion/removal of the optical member in/from the optical path.
Further features of the present invention will be apparent from the following description of exemplary embodiments with reference to the attached drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing an example of the arrangement of an ophthalmic apparatus;
FIG. 2 is a view for explaining a stop 207;
FIG. 3 is a view for explaining an alignment prism stop 223;
FIG. 4 is a block diagram showing the arrangement of the ophthalmic apparatus;
FIG. 5 is a view for explaining an observation image;
FIG. 6 is a flowchart showing a processing procedure concerning the detection of the operation of inserting/removing an optical member in/from an optical path; and
FIG. 7 is a view showing an example of the images captured by image sensors 210 and 220.



DESCRIPTION OF THE EMBODIMENTS
An exemplary embodiment(s) of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.
(Arrangement of Ophthalmic Apparatus)
The schematic arrangement of an ophthalmic refractive power measuring device as an example of an ophthalmic apparatus will be described with reference to FIG. 1. A lens 202, a stop 203 almost conjugate to a pupil Ep of an eye E to be examined, a perforated mirror 204, a diffusing plate 222, a lens 205, and a dichroic mirror 206 which totally reflects infrared light and visible light, from the eye E side, which have wavelengths equal to or less than 880 nm and partly reflects a light flux having a wavelength equal to or more than 880 nm are sequentially arranged to form a measurement light projection optical system on an optical path 01 extending from an ocular refractive power measurement light source 201, which emits light having a wavelength of 880 nm, to the eye E. Also, the measurement light projection optical system can be referred to as an illumination optical system in the specification.
A stop 207 having an annular aperture almost conjugate to a cornea Ec, a light flux spectral prism 208, a lens 209, and an image sensor 210 are sequentially arranged to form a measurement light receiving optical system on an optical path 02 in the reflecting direction of the perforated mirror 204. Also, the measurement light receiving optical system can be referred to as an imaging optical system in the specification.
The above optical system is used for ocular refractive power measurement. The stop 203 limits the light flux emitted by the measurement light source 201. The lens 202 performs primary image formation of the light in front of the lens 205. The resultant light is then transmitted through the lens 205 and the dichroic mirror 206 to be projected on the pupil center of the eye E.
A fundus Er of the eye E reflects the projected light flux. The fundus reflected light strikes the lens 205 again through the pupil center. The incident light flux is transmitted through the lens 205 and then reflected by the periphery of the perforated mirror 204.
The reflected light flux is separated by the conical light flux spectral prism 208 using the Gullstrand's principle through the stop 207 provided at a position almost conjugate to the cornea Ec of the eye to be examined. The resultant light is projected as a ring image on the light receiving surface of the image sensor 210. If the eye E is an emmetropic eye, this ring image becomes a predetermined circular shape. If the eye E is a myopic eye, the projected image has a circular shape smaller than that of the emmetropic eye. If the eye E is a hyperopic eye, the projected image has a circular shape larger than that of the emmetropic eye. If the eye E has astigmatism, the ring image has an elliptic shape. The angle defined by the horizontal axis and the ellipse indicates an astigmatic axis angle. It is possible to obtain a refractive power based on this elliptic coefficient.
A diffusing plate insertion/removal unit 301 (to be described later with reference to FIG. 4) allows the diffusing plate 222 to be detachably inserted/removed in/from a position in an optical path shared by the measurement light projection optical system and the measurement light receiving optical system. Inserting/removing operation will be described in detail later.
As shown in FIG. 2, the stop 207 is constituted by two stops including annular aperture portions having different sizes. Each stop has upper and lower holding portions k for holding a central portion d1. This apparatus performs measurement upon switching two stops 207a and 207b of the stop 207 in accordance with the size of the cornea Ec (or the pupil Ep) of the eye E.
The stops 207a and 207b have apertures with orbicular zone shapes. Inner diameters d1 of these stops are the same. The outer diameters of the stops are expressed as d2>d3. In general, the apparatus performs measurement while the stop 207a is inserted in the optical path 02. If, however, the pupil Ep of the eye E is small in size and the outer diameter d2 of an image formed on the pupil Ep has a size d2′ expressed as d2′>size of pupil Ep, the ring image on the image sensor 210 changes in brightness and size. This leads to incorrect measurement. In such a case, the apparatus performs measurement upon making a stop insertion/removal unit 302 (to be described later with reference to FIG. 4) switch from the stop 207a to the stop 207b. 
A fixation target projection optical system and an alignment light receiving optical system commonly used for the anterior ocular segment observation of the eye E and alignment detection are arranged in the reflecting direction of the dichroic mirror 206. A lens 211, a dichroic mirror 212, a lens 213, a folding mirror 214, a lens 215, a fixation target 216, and a fixation target illumination light source 217 are sequentially arranged on an optical path 03 of the fixation target projection optical system.
At the time of eye fixation induction, a projection light flux from the turned-on fixation target illumination light source 217 illuminates the fixation target 216 from its rear side and is projected on the fundus Er of the eye E through the lens 215, the folding mirror 214, the lens 213, the dichroic mirror 212, and the lens 211. Note that a fixation induction motor 224 can move the lens 215 in the optical axis direction to implement a fogging state by performing diopter induction of the eye E.
An alignment prism stop 223 to be inserted/removed by an alignment prism stop insertion/removal unit 303 (to be described with reference to FIG. 4), a lens 218, a kerato stop 503 for kerato measurement which is detachably inserted/removed in/from the optical path by a kerato stop insertion/removal unit 304 (to be described later with reference to FIG. 4), and an image sensor 220 are sequentially arranged on an optical path 04 in the reflecting direction of the dichroic mirror 212.
Inserting/removing the alignment prism stop 223 allows performance of alignment when the alignment prism stop 223 is located on the optical path 04 and performance of anterior ocular segment observation or transillumination observation when the alignment prism stop 223 is removed from the optical path. Anterior ocular segment illumination light sources 221a and 221b, each having a wavelength of about 780 nm, are arranged diagonally forward of the eye E.
The shape of the alignment prism stop 223 will be described with reference to FIG. 3. A disc-like stop plate of the alignment prism stop 223 is provided with three aperture portions 223a, 223b, and 223c for the restriction of light fluxes. Alignment prisms 301a and 301b which transmit only light fluxes near a wavelength of 880 nm are respectively bonded to the aperture portions 223a and 223b on the two sides which are located on the dichroic mirror 212 side.
The kerato stop 503 is a stop for corneal shape measurement. The kerato stop insertion/removal unit 304 inserts the kerato stop 503 in the optical path when the apparatus measures the curvature radius of the cornea Ec of the eye E. The kerato stop 503 is a small aperture stop which is provided so as to select the same principal ray (light flux) of the light fluxes emitted by a kerato measurement light source 290, which illuminates the cornea Ec of the eye E in a ring form, and reflected by the cornea Ec, even if the distance (operating distance) between the cornea Ec of the eye E and the kerato measurement light source 290 slightly deviates from a set value. This makes the size of the ring image captured by the image sensor 220 remain the same regardless of whether the operating distance slightly deviates, and hence can obtain an accurate curvature radius value (kerato value).
FIG. 5 shows an example of an observation image displayed on an LCD monitor 403 (to be described later with reference to FIG. 4). Anterior ocular segment image light fluxes from the eye E illuminated by the anterior ocular segment illumination light sources 221a and 221b are formed into images on the light receiving sensor surface of the image sensor 220 through the dichroic mirror 206, the lens 211, the dichroic mirror 212, and the central aperture portion 223c of the alignment prism stop 223.
The ocular refractive power measurement light source 201 also serves as a light source for alignment detection. At the time of alignment, the diffusing plate insertion/removal unit 301 inserts the translucent diffusing plate 222 in the optical path 01. The insertion position of the diffusing plate 222 almost coincides with the primary image formation position of the projection lens 202 of the measurement light source 201 described above and also coincides with the focal position of the lens 205. This temporarily forms light from the measurement light source 201 into an image on the diffusing plate 222. This image then serves as a secondary light source and is projected as a thick parallel light flux propagating from the lens 205 to the eye E.
The cornea Ec of the eye E reflects this parallel light flux to form a bright spot image. The dichroic mirror 206 partly reflects this light flux again. The light fluxes is reflected by the dichroic mirror 212 through the lens 211, and is transmitted through the aperture portions 223a, 223b, and 223c of the alignment prism stop 223 and the alignment prisms 301a and 301b. The lens 218 focuses the light fluxes to form images Ta, Tb, and Tc on the image sensor 220.
The central aperture portion 223c of the alignment prism stop 223 is designed to transmit light fluxes having a wavelength of 780 nm or more from the anterior ocular segment illumination light sources 221a and 221b. The reflected light fluxes of the anterior ocular segment images illuminated by the anterior ocular segment illumination light sources 221a and 221b propagate along same path in the observation optical system as that of the reflected light fluxes from the cornea Ec. The imaging lens 218 then forms these reflected light fluxes into images 221a′ and 221b′ on the image sensor 220 through the aperture portion 223c of the alignment prism stop 223. It is possible to align the eye E based on the positional relationship between the respective light fluxes obtained through these stops.
Referring to FIG. 1, a mask 501 provided on an optical path 05 and a light source 502 which is located near the diffusing plate and illuminates the mask 501 constitute a temperature-compensation optical system on the transmission side of the optical path 04 relative to the dichroic mirror 206. As indicated by “707” in FIG. 7, the mask 501 has four aperture portions around the optical axis and is placed at a position almost conjugate to the cornea Ec of the eye E on the optical path 05.
When, for example, the housing or the like expands or shrinks due to a change in ambient temperature, the optical imaging relationship changes at the time of kerato measurement. This will change the size of a kerato image formed on the image sensor 220. The temperature-compensation optical system is an optical system for compensating for a change in measurement value due to a change in the size of the kerato image. The apparatus turns on the light source 502 before kerato measurement and performs imaging by using the image sensor 220 while a kerato stop 503 is inserted in the optical path. The apparatus compares the intervals between the four aperture portions of the mask 501, whose image has been captured, with the intervals of the aperture portions which have been analyzed and stored in advance, and corrects the kerato measurement value based on the change amount. This makes it possible to calculate a correct kerato measurement value even if the ambient temperature changes.
FIG. 4 is a block diagram of the ophthalmic apparatus. The ophthalmic apparatus includes a control unit 401, a light source driving circuit 402, the LCD monitor 403, a storage unit 404, a memory 405, the diffusing plate insertion/removal unit 301, the stop insertion/removal unit 302, the alignment prism stop insertion/removal unit 303, the kerato stop insertion/removal unit 304, a notification unit 305, and a temporal change storage unit 306.
The control unit 401 controls the overall ophthalmic apparatus, and includes a program storage unit, a data storage unit which stores data for the correction of ocular refractive power values, an input/output control unit which controls input/output operation with respect to various types of devices, and an arithmetic processing unit which computes data obtained from various types of devices (none of which are shown). The light source driving circuit 402 controls ON/OFF operation or change in light amount for the measurement light source 201, the anterior ocular segment illumination light source 221a, the anterior ocular segment illumination light source 221b, the fixation target illumination light source 217, the kerato measurement light source 290, and the light source 502 in accordance with commands from the control unit 401. The LCD monitor 403 displays the anterior ocular segment image captured by the image sensor 220, measurement values, and the like under the control of the control unit 401 which functions as a display control unit. The storage unit 404 stores predetermined values for the determination of the quality of images captured at the time of the insertion and removal of various optical members (the diffusing plate 222, the stop 207, the alignment prism stop 223, the kerato stop 503, and the like) which are inserted/removed in/from optical paths (to be described later). The memory 405 stores the anterior ocular segment image of the eye E captured by the image sensor 220. The apparatus performs alignment detection by extracting the pupil Ep of the eye E and a cornea reflection image from the image stored in the memory 405. The anterior ocular segment image of the eye E captured by the image sensor 220 is combined with character data and graphic data. The LCD monitor 403 then displays the combined anterior ocular segment image, measurement values, and the like. The memory 405 stores the ocular refractive power calculation ring image captured by the image sensor 210.
The diffusing plate insertion/removal unit 301, the stop insertion/removal unit 302, the alignment prism stop insertion/removal unit 303, and the kerato stop insertion/removal unit 304 perform inserting/removing operation for the respective insertion/removal targets under the control of the control unit 401. The diffusing plate insertion/removal unit 301 functions as an optical member insertion/removal unit, and inserts/removes the diffusing plate 222 in/from a position in the optical path which is shaped by the measurement light projection optical system and the measurement light receiving optical system. The stop insertion/removal unit 302 functions as an optical member insertion/removal unit, and inserts/removes the stops 207a and 207b of the stop 207 in/from the optical path upon switching between them. The alignment prism stop insertion/removal unit 303 functions as an optical member insertion/removal unit and inserts/removes the alignment prism stop 223 in/from the optical path. The alignment prism stop insertion/removal unit 303 functions as an optical member insertion/removal unit, and inserts/removes the kerato stop 503 for kerato measurement in/from the optical path. The notification unit 305 has a function of notifying an examiner of an abnormality at the time of checking of the insertion/removal of an optical member under the control of the control unit 401. The notification unit 305 may perform notification by sound or displaying an insertion/removal check result on the LCD monitor 403. Alternatively, the notification unit 305 may be configured to notify the examiner of normal operation instead of an abnormality. That is, the notification unit 305 may perform notification in any manner as long as it is configured to notify the state of insertion/removal of an optical member in/from an optical path. The temporal change storage unit 306 stores a normal/abnormal determination result on inserting/removing operation for each optical member. Upon receiving a request to output temporal change information from the examiner or another user, the control unit 401 reads out the corresponding temporal change information from the temporal change storage unit 306, and outputs a display form indicating the temporal change via the LCD monitor 403 or a separately provided output terminal.
A processing procedure at the time of the inserting/removing operation for each of the diffusing plate 222, the stop 207, the alignment prism stop 223, and the kerato stop 503 will be described below with reference to the flowchart of FIG. 6. When the examiner turns on the power supply of the ophthalmic apparatus before the processing, the control unit 401 performs an operation check on each driving unit.
First Embodiment
Detection of Inserting/Removing Operation for Diffusing Plate 222 with Respect to Optical Path
The first embodiment will be described below with reference to FIG. 6, in which inserting/removing operation for the diffusing plate 222 as an example of an optical member with respect to the optical path is detected.
(Processing to be Performed when Diffusing Plate 222 is Removed from Optical Path)
A processing procedure at the time of the removal of the diffusing plate 222 will be described with reference to the flowchart of FIG. 6. In step S601, the control unit 401 controls the light source driving circuit 402 to turn on the measurement light source 201 to emit a predetermined amount of light, and controls the stop insertion/removal unit 302 to insert the stop 207a in the optical path. The control unit 401 then controls the diffusing plate insertion/removal unit 301 to remove the diffusing plate 222 out of the optical path.
In step S602, the image sensor 210 performs imaging in synchronism with the removal of the diffusing plate 222. The memory 405 stores a captured image. The image obtained in this case depicts nothing as indicated by “701” in FIG. 7 because measurement light is transmitted through the lens 205 and emerges out of the ophthalmic apparatus and hence no reflected light reaches the image sensor 210.
In step S603, the control unit 401 reads out a predetermined value at the time of the removal of the diffusing plate 222 from the storage unit 404. As the predetermined value at the time of removal, the standard deviation, maximum luminance value, or the like of the luminance distribution of the acquired image is set.
In step S604, the control unit 401 compares the image analysis result obtained in step S602 with the predetermined value read out in step S603 to determine, based on the comparison result, whether the operation (the removing operation for the diffusing plate 222) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation result is normal (YES in step S604), and the process advances to step S605. If the control unit 401 determines that the operation result is abnormal (NO in step S604), the process advances to step S606.
In step S605, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S606, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal. With the above operation, each process in the flowchart of FIG. 6 is complete.
(Processing to be Performed when Diffusing Plate 222 is Inserted in Optical Path)
A processing procedure at the time of the insertion of the diffusing plate 222 will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S611 to S615. In step S611, the control unit 401 controls the light source driving circuit 402 to turn on the measurement light source 201 to emit a predetermined amount of light, and controls the stop insertion/removal unit 302 to insert the stop 207a in the optical path. The control unit 401 then controls the diffusing plate insertion/removal unit 301 to insert the diffusing plate 222 in the optical path.
In step S612, the image sensor 210 performs imaging in synchronism with the insertion of the diffusing plate 222. The memory 405 stores a captured image. If the diffusing plate 222 is correctly inserted in the optical path, the light flux emitted by the measurement light source 201 is diffused by the diffusing plate 222. The diffusing plate 222 then serves as a diffusing light source. The reflected light from this light source is transmitted through the perforated mirror 204, the stop 207 (assume that the stop 207a is inserted in the optical path), the light flux spectral prism 208, and the lens 209 to be captured by the image sensor 210. The image obtained in this case has a ring-like shape as indicated by “702” in FIG. 7. Since the stop 207 has the holding portions k, the captured image has the shadows of the holding portions k at upper and lower positions.
In step S613, the control unit 401 reads out a predetermined value at the time of the insertion of the diffusing plate 222 from the storage unit 404. Since the position of the diffusing plate 222 on the optical axis is determined in advance, the size or luminance of the ring image to be captured when the diffusing plate 222 is normally inserted in the optical path is known. For this reason, the diameter or luminance distribution of an approximate circle of the ring image is set as the predetermined value at the time of insertion.
In step S614, the control unit 401 compares the image analysis result obtained in step S612 with the predetermined value read out in step S613 to determine, based on the comparison result, whether the operation (the inserting operation for the diffusing plate 222) has been normally performed. The control unit 401 compares the analyzed diameter or luminance distribution with the diameter or luminance distribution stored in the storage unit 404. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S614), the process advances to step S615. If the control unit 401 determines that the operation result is abnormal (NO in step S614), the process advances to step S616.
In step S615, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S616, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
Second Embodiment
Detection of Inserting/Removing Operation for Stop 207 with Respect to Optical Path
The second embodiment will be described below with reference to FIG. 6, in which inserting/removing operation for the stop 207 as an example of an optical member with respect to the optical path is detected.
(Processing to be Performed when Stop 207a is Inserted in Optical Path)
A processing procedure at the time of the insertion of the stop 207a will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S801 to S805. In step S801, the control unit 401 controls the light source driving circuit 402 to turn on the measurement light source 201 to emit a predetermined amount of light, and controls the diffusing plate insertion/removal unit 301 to remove the diffusing plate 222 from the optical path. The control unit 401 then controls the stop insertion/removal unit 302 to insert the stop 207a in the optical path. Note that the control unit 401 may detect that the stop 207b is removed from the optical path.
In step S802, the image sensor 210 performs imaging in synchronism with the insertion of the stop 207a. The memory 405 stores a captured image. The image obtained in this case has a ring-like shape as indicated by “702” in FIG. 7. Since the stop 207 has the holding portions k, the captured image has the shadows of the holding portions k at upper and lower positions.
In step S803, the control unit 401 reads out a predetermined value at the time of the insertion of the stop 207a from the storage unit 404. The luminance value or the like of the acquired image is set as the predetermined value at the time of insertion. The stops 207a and 207b have different aperture areas. Even if, therefore, the sizes of the ring images are the same, they differ in luminance. For this reason, a luminance value is set as the predetermined value. Assume that some problem has occurred at the stop insertion/removal unit 302, and the stop 207a is not completely inserted or removed in or from the optical path. In this case, as indicated by “708” in FIG. 7, since the shadows of the holding portions k of the stop 207a on the ring image change in position, the position of a shadow on the ring image may be set as the predetermined value. Alternatively, when the diffusing plate 222 is inserted at a position deviating from the focal position of the lens 205, the size of the captured ring image changes. Therefore, the diameter of an approximate circle of the ring image may be set as the predetermined value.
In step S804, the control unit 401 compares the image analysis result obtained in step S802 with the predetermined value read out in step S803 to determine, based on the comparison result, whether the operation (the inserting operation for the stop 207a) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S804), the process advances to step S805. If the control unit 401 determines that the operation result is abnormal (NO in step S804), the process advances to step S806.
In step S805, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S806, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
(Processing to be Performed when Stop 207b is Inserted in Optical Path)
A processing procedure at the time of the insertion of the stop 207b will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S811 to S815. In step S811, the control unit 401 controls the light source driving circuit 402 to turn on the measurement light source 201 to emit a predetermined amount of light, and controls the diffusing plate insertion/removal unit 301 to remove the diffusing plate 222 from the optical path. The control unit 401 then controls the stop insertion/removal unit 302 to switch from the stop 207a to the stop 207b having a smaller outer diameter and insert the stop 207b in the optical path. Note that the control unit 401 may detect that the stop 207a is removed from the optical path.
In step S812, the image sensor 210 performs imaging in synchronism with the insertion of the stop 207b. The memory 405 stores a captured image. The image obtained in this case has a ring-like shape as indicated by “703” in FIG. 7. Since the stop 207b has the holding portions k, the captured image has the shadows of the holding portions k at upper and lower positions. Note however that since the stop 207b is smaller in aperture area than the stop 207a, the luminance of the ring image is lower than that of the ring image indicated by “702”.
In step S813, the control unit 401 reads out a predetermined value at the time of the insertion of the stop 207b from the storage unit 404. The luminance value or the like of the acquired image is set as the predetermined value at the time of insertion as in the case of the stop 207a. In step S814, the control unit 401 compares the image analysis result obtained in step S812 with the predetermined value read out in step S813 to determine, based on the comparison result, whether the operation (the inserting operation for the stop 207b) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S814), the process advances to step S815. If the control unit 401 determines that the operation result is abnormal (NO in step S814), the process advances to step S816.
In step S815, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S816, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
Note that the above operation detection processing for the stop 207 may be performed following the operation detection processing for the diffusing plate 222. For example, this operation may be performed during aligning operation for the eye to be examined.
Third Embodiment
Detection of Inserting/Removing Operation for Alignment Prism Stop 223 with Respect to Optical Path
The third embodiment will be described below with reference to FIG. 6, in which inserting/removing operation for the alignment prism stop 223 as an example of an optical member with respect to the optical path is detected.
(Processing to be Performed when Alignment Prism Stop 223 is Removed from Optical Path)
A processing procedure at the time of the removal of the alignment prism stop 223 will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S901 to S905. In step S901, the control unit 401 controls the light source driving circuit 402 to turn off the measurement light source 201 and the kerato measurement light source 290 and turn on the light source 502. The control unit 401 also controls the kerato stop insertion/removal unit 304 to insert the kerato stop 503 in the optical path. In addition, the control unit 401 controls the alignment prism stop insertion/removal unit 303 to remove the alignment prism stop 223 from the optical path. Note that the position of the diffusing plate 222 is arbitrary.
In step S902, the image sensor 220 images the mask 501 of the temperature-compensation optical system in synchronism with the removal of the alignment prism stop 223. The memory 405 stores a captured image. The image obtained in this case clearly depicts the four aperture portions of the mask 501 as indicated by “704” in FIG. 7.
In step S903, the control unit 401 reads out a predetermined value at the time of the removal of the alignment prism stop 223 from the storage unit 404. The distance among the centroids of four aperture portion images, a luminance value, the difference between the left and right or the upper and lower aperture portion images, vignetting of a bright spot, or the like is set as the predetermined value at the time of removal.
In step S904, the control unit 401 compares the image analysis result obtained in step S902 with the predetermined value read out in step S903 to determine, based on the comparison result, whether the operation (the removing operation for the alignment prism stop 223) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the alignment prism stop 223 has not been normally removed, since the left and right or the upper and lower of four aperture portion images differ in luminance value or vignetting occurs, it is possible to detect normal/abnormal removal. If the control unit 401 determines that the operation result is normal (YES in step S904), the process advances to step S905. If the control unit 401 determines that the operation result is abnormal (NO in step S904), the process advances to step S906.
In step S905, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S906, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
(Processing to be Performed when Alignment Prism Stop 223 is Inserted in Optical Path)
A processing procedure at the time of the insertion of the alignment prism stop 223 will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S911 to S915. In step S911, the control unit 401 controls the light source driving circuit 402 to turn off the measurement light source 201 and the kerato measurement light source 290 and turn on the light source 502. The control unit 401 also controls the kerato stop insertion/removal unit 304 to insert the kerato stop 503 in the optical path. The control unit 401 also controls the alignment prism stop insertion/removal unit 303 to insert the alignment prism stop 223 from the optical path. Note that the position of the diffusing plate 222 is arbitrary.
In step S912, the image sensor 220 performs imaging in synchronism with the insertion of the alignment prism stop 223. The memory 405 stores a captured image. The three stops of the aperture portions 223a, 223b, and 223c of the alignment prism stop 223 receive light fluxes. Since the alignment prisms 301a and 301b are respectively bonded to the aperture portions 223a and 223b, the light fluxes passing through the aperture portions 223a and 223b are separated to the right and left. For this reason, the image obtained in this case depicts the four aperture portions of the mask 501 with each being separated into three portions, as indicated by 705 in FIG. 7.
In step S913, the control unit 401 reads out a predetermined value at the time of the insertion of the alignment prism stop 223 from the storage unit 404. The number of separated portions of the four aperture portion images, the distance among the centroids of the four aperture portion images formed by the light fluxes transmitted through the aperture portion 223c of the alignment prism stop 223, a luminance value, the difference in luminance value between the left and right or the upper and lower portions of 12 aperture portion images, a vignetting amount, or the like is set as the predetermined value at the time of insertion.
In step S914, the control unit 401 compares the image analysis result obtained in step S912 with the predetermined value read out in step S913 to determine, based on the comparison result, whether the operation (the inserting operation for the alignment prism stop 223) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S914), the process advances to step S915. If the control unit 401 determines that the operation result is abnormal (NO in step S914), the process advances to step S916.
In step S915, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S916, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
Note that the control unit 401 may be configured to check insertion/removal by comparing the image captured in step S902 with the image captured in step S912 and performing determination operation by determining the normal/abnormal operation of the alignment prism stop 223 based on the number of aperture portion images detected or a luminance value difference.
Fourth Embodiment
Detection of Inserting/Removing Operation for Kerato Stop 503 with Respect to Optical Path
The fourth embodiment will be described below with reference to FIG. 6, in which inserting/removing operation for the kerato stop 503 as an example of an optical member with respect to the optical path is detected.
(Processing to be Performed when Kerato Stop 503 is Inserted in Optical Path)
A processing procedure at the time of the insertion of the kerato stop 503 will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S1101 to S1105. In step S1101, the control unit 401 controls the light source driving circuit 402 to turn off the measurement light source 201 and the kerato measurement light source 290 and turn on the light source 502. The control unit 401 also controls the alignment prism stop insertion/removal unit 303 to remove the alignment prism stop 223 from the optical path. Note that the position of the diffusing plate 222 is arbitrary. In addition, the control unit 401 controls the kerato stop insertion/removal unit 304 to insert the kerato stop 503 in the optical path. In step S1102, the image sensor 220 images the mask 501 of the temperature-compensation optical system in synchronism with the insertion of the kerato stop 503. The memory 405 stores a captured image. The image obtained in this case is the same as that obtained in step S902. If, therefore, the processing in step S902 has already been performed, the corresponding image may also be used in this processing. That is, the processing in step S1102 may be omitted.
In step S1103, the control unit 401 reads out a predetermined value at the time of the insertion of the kerato stop 503 from the storage unit 404. The distance among the centroids of four aperture portion images, a luminance value, the difference in luminance value between the left and right or the upper or lower images of the four aperture portion images, a vignetting amount, or the like is set as the predetermined value at the time of insertion.
In step S1104, the control unit 401 compares the image analysis result obtained in step S1102 with the predetermined value read out in step S1103 to determine, based on the comparison result, whether the operation (the inserting operation for the kerato stop 503) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S1104), the process advances to step S1105. If the control unit 401 determines that the operation result is abnormal (NO in step S1104), the process advances to step S1106.
In step S1105, the control unit 401 stores the current image analysis result in the temporal change storage unit 306. In step S1106, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
(Processing to be Performed when Kerato Stop 503 is Removed from Optical Path)
A processing procedure at the time of the removal of the kerato stop 503 will be described next, with the operations in steps S601 to S605 in the flowchart of FIG. 6 being replaced with those in steps S1111 to S1115. In step S1111, the control unit 401 controls the light source driving circuit 402 to turn off the measurement light source 201 and the kerato measurement light source 290 and turn on the light source 502. The control unit 401 also controls the alignment prism stop insertion/removal unit 303 to remove the alignment prism stop 223 from the optical path. Note that the position of the diffusing plate 222 is arbitrary. In addition, the control unit 401 controls the kerato stop insertion/removal unit 304 to remove the kerato stop 503 from the optical path.
In step S1112, the image sensor 220 images the mask 501 of the temperature-compensation optical system in synchronism with the removal of the kerato stop 503. The memory 405 stores a captured image. The image obtained in this case depicts aperture images at four portions as in the case of the image indicated by “704” in FIG. 7, as indicated by 706 in FIG. 7. Larger aperture images are observed from this image for the following reason. The pupil diameter has increased upon removal of the alignment prism stop 223 from the optical path, and the light amount has increased to increase the luminance value.
In step S1113, the control unit 401 reads out a predetermined value at the time of the removal of the kerato stop 503 from the storage unit 404. The luminance value of an aperture portion image, the difference in luminance value between the left and right or the upper and lower images of the fourth aperture portion images, a vignetting amount, or the like is set as the predetermined value at the time of removal.
In step S1114, the control unit 401 compares the image analysis result obtained in step S1112 with the predetermined value read out in step S1113 to determine, based on the comparison result, whether the operation (the removing operation for the kerato stop 503) has been normally performed. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit 401 determines that the operation result is normal (YES in step S1114), the process advances to step S1115. If the control unit 401 determines that the operation result is abnormal (NO in step S1114), the process advances to step S1116.
In step S1115, the control unit 401 stores the current image analysis result in the temporal change storage unit 306 as the second storage unit. In step S1116, the control unit 401 controls the notification unit 305 to notify the examiner that the operation is abnormal.
Note that the control unit 401 may be configured to check insertion/removal by comparing the image captured in step S1102 with the image captured in step S1112 and performing determination operation by determining the normal/abnormal operation of the kerato stop 503 based on the number of aperture portion images detected or a luminance value difference.
Note that an operation check is not limited to the order of processing described above. The time when an operation check is performed is not limited to the time of power-on. That is, an operation check may be performed before the execution of measurement or for each examiner. The apparatus may be configured to make the notification unit notify a temporal change when an abnormality has occurred or to notify a temporal change at a periodic check. Although the above description has exemplified the arrangement for performing insertion/removal determination based on an image analysis result, it is possible to perform insertion/removal determination based on a signal acquired from the image sensor in synchronism with insertion/removal. The apparatus may perform insertion/removal determination by comparing a signal acquired from the image sensor with a signal held in advance which should be acquired. Alternatively, the apparatus may perform insertion/removal determination based on the difference between signals obtained from the image sensor at time of insertion and the time of removal.
Note that the ophthalmic apparatus which measures the ocular refractive power of the eye to be examined may include a detection unit such as a dedicated microswitch or photointerrupter to check whether an optical member such as a stop or diffusing plate is reliably inserted or removed, when implementing an arrangement suitable for a measurement mode by inserting or removing the optical member in or from the optical path. In contrast to this, this apparatus may not include any dedicated detection unit as in this embodiment.
As described above, the ophthalmic apparatus according to this embodiment checks inserting/removing operation for an optical member with respect to the optical path by using the light source for ocular characteristic measurement and the image sensor for detection, and hence it is possible to find a failure of the insertion/removal of the optical member due to temporal deterioration. In addition, this apparatus need not separately include any dedicated detection unit, and hence allows decreasing of the number of components. It is also unnecessary to ensure any space for the installation of a detection unit. It is therefore possible to downsize the apparatus. Furthermore, since the notification unit notifies the examiner of an operation failure, the examiner can avoid a measurement error. This can reduce measurement errors and burden on the examiner.
In addition, it is possible to check inserting/removing operation at the time of power-on. This makes it possible to perform an operation check as a part of initialization for the ophthalmic apparatus. Furthermore, it is possible to avoid the prolongation of measurement because an operation check is not frequently performed.
An inserting/removing operation check may be performed before the projection of a light flux. This can prevent the occurrence of a measurement error at the time of the use of the ophthalmic apparatus.
If an optical member for which an inserting/removing operation check is performed is a diffusing plate, it is possible to eliminate any measurement errors when performing ocular refractive power measurement and to avoid problems such as a decrease in the detection range of bright spot images at the time of alignment.
Assume that optical members for which an inserting/removing operation check is to be performed are a plurality of stops (stops 207a and 207b) which are used for ocular refractive power measurement and can be switched. In this case, if the pupil diameter of an object is small, it is possible to switch to a more suitable stop.
In addition, the apparatus may execute an inserting/removing operation check for the ocular refractive power measurement stop while performing alignment (aligning operation). At the time of alignment, an optical member such as the diffusing plate is inserted in the optical path, and the light source for ocular refractive power measurement is turned on. This makes it possible to easily perform a check by using the ocular refraction measurement image sensor. It is therefore possible to shorten the initialization time or the time for checking operation before measurement.
Using aperture portion images illuminated by light, as an operation check light flux, from the optical system light source of the temperature-compensation optical system will eliminate the necessity to provide any new light source.
Assume that an optical member for which an insertion/removal check is to be performed is the alignment prism stop. In this case, if an anterior ocular segment image is free from overexposure, and an alignment aperture and a prism are integrated, since it is possible to check that the alignment aperture is located at a correct position, it is possible to perform accurate alignment.
In addition, if an optical member for which an insertion/removal check is to be performed is a kerato stop for kerato measurement, the apparatus is free from any kerato measurement errors due to stop insertion/removal failures.
Furthermore, since the ophthalmic apparatus checks a temporal change and stores the operation check result, it is possible to easily check the state of the ophthalmic apparatus when performing maintenance. Since the operation check light source and the image sensor also serve as a measurement light source and an image sensor, it is possible to avoid the complexity of the ophthalmic apparatus.
Note that the present invention may execute each embodiment described above or all the embodiments. The present invention may execute at least one of the embodiments. For example, it is possible to execute both detection of inserting/removing operation for the alignment prism stop 223 with respect to the optical path and detection of inserting/removing operation for the kerato stop 503 with respect to the optical path.
According to the present invention, it is possible to find a failure of the insertion/removal of an optical member due to temporal deterioration.
Other Embodiments
Aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment(s), and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment(s). For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (for example, computer-readable storage medium).
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-031045 filed on Feb. 15, 2012, which is hereby incorporated by reference herein in its entirety.

## Claims

1. An ophthalmic apparatus comprising:
an illumination optical system including a light source and configured to illuminate an eye to be examined;
an imaging optical system including an image sensor, the image sensor imaging the eye illuminated by the illumination optical system;
a plurality of optical member insertion/removal units configured to insert/remove a plurality of optical members in/from at least one of optical paths in the illumination optical system and the imaging optical system;
a control unit configured to control the optical member insertion/removal units so as to insert/remove the optical members in/from the at least one optical path;
a determination unit configured to determine whether or not insertion/removal of each optical member in/from an optical path has been normally performed, based on an analysis result of an image corresponding to each optical member obtained by the image sensor in synchronism with insertion/removal of each optical member in/from the optical path; and
a notification unit configured to notify an abnormality in a case where the determination unit has determined that insertion/removal of at least one of the plurality of optical members in/from the optical path has not been normally performed.

2. The apparatus according to claim 1, wherein the determination unit determines whether the inserting/removing operation has been normally performed, based on comparison between a predetermined value and an analysis result on an image captured by the image sensor in synchronism with the inserting/removing operation.

3. The apparatus according to claim 2, further comprising:
a storage unit configured to store, as a temporal change, a comparison result between a predetermined value and an analysis result on an image captured by the image sensor; and
a display control unit configured to cause a display unit to display a display form indicating the comparison result stored in the storage unit.

4. The apparatus according to claim 1, wherein the control unit controls the optical member insertion/removal units so as to insert/remove the optical members in/from the optical path at the time of power-on of the ophthalmic apparatus.

5. The apparatus according to claim 1, wherein the control unit controls the optical member insertion/removal units so as to insert/remove the optical members in/from the optical path before the illumination optical system illuminates the eye.

6. The apparatus according to claim 1, wherein one of the optical members comprises a diffusing plate provided on an optical path shared by the illumination optical system and the imaging optical system, and
wherein the image sensor comprises an image sensor for ocular refractive power measurement.

7. The apparatus according to claim 1, wherein one of the optical members comprises a plurality of stops which are configured to be switchable and provided at a position substantially conjugate to the eye in the imaging optical system configured to perform ocular refractive power measurement, and
wherein the image sensor comprises an image sensor for ocular refractive power measurement.

8. The apparatus according to claim 7, wherein the determination unit performs determination at the time of aligning operation for the eye.

9. The apparatus according to claim 2, further comprising a temperature-compensation optical system including a mask which includes a plurality of aperture portions and placed at a position conjugate to a cornea of the eye and an optical system light source configured to illuminate the mask,
wherein the imaging optical system is commonly used as an imaging optical system of the temperature-compensation optical system, and
wherein the determination unit determines whether the inserting/removing operation has been normally performed, based on a comparison between a predetermined value and an analysis result on an image obtained by causing the image sensor to capture a light from the optical system light source in synchronism with inserting/removing operation for the optical member.

10. The apparatus according to claim 9, wherein one of the optical members comprises an alignment prism stop which is provided in the imaging optical system and configured to restrict a light flux.

11. The apparatus according to claim 9, wherein one of the optical members comprises a stop for cornea shape measurement which is provided between an imaging lens of the imaging optical system and the image sensor and configured to measure a curvature radius value of the cornea of the eye.

12. The apparatus according to claim 1, wherein a light source and an image sensor which are configured to check inserting/removing operation for the optical members are commonly used as a measurement light source and an image sensor which are configured to measure an ocular characteristic of the eye.

13. A method for controlling an ophthalmic apparatus, the method comprising:
controlling a plurality of optical member insertion/removal units configured to insert/remove a plurality of optical members in/from at least one of optical paths in an illumination optical system including a light source and configured to illuminate an eye to be examined and an imaging optical system including an image sensor, the image sensor imaging the eye illuminated by the illumination optical system;
determining whether or not insertion/removal of each optical member in/from the at least one optical path has been normally performed, based on an analysis result of an image corresponding to each optical member obtained by the image sensor in synchronism with insertion/removal of each optical member in/from the at least one optical path; and
notifying an abnormality in a case where it is determined in the step of determining that insertion/removal of at least one of the plurality of optical members in/from the at least one optical path has not been normally performed.

14. The apparatus according to claim 1, wherein the control unit controls the optical member insertion/removal units so as to insert/remove the optical members in/from the optical path when performing an alignment of the ophthalmic apparatus with respect to the eye to be examined.

15. The method according to claim 13, wherein in the step of controlling, the optical member insertion/removal units is controlled so as to insert/remove the optical members in/from the optical path when performing an alignment of the ophthalmic apparatus with respect to the eye to be examined.

16. The method according to claim 13, wherein in the step of controlling, the optical member insertion/removal units is controlled so as to insert/remove the optical members in/from the optical path at the time of power-on of the ophthalmic apparatus.