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

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 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.

DESCRIPTION OF THE EMBODIMENTS

The schematic arrangement of an ophthalmic refractive power measuring device as an example of an ophthalmic apparatus will be described with reference toFIG. 1. A lens202, a stop203almost conjugate to a pupil Ep of an eye E to be examined, a perforated mirror204, a diffusing plate222, a lens205, and a dichroic mirror206which 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 path01extending from an ocular refractive power measurement light source201, 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 stop207having an annular aperture almost conjugate to a cornea Ec, a light flux spectral prism208, a lens209, and an image sensor210are sequentially arranged to form a measurement light receiving optical system on an optical path02in the reflecting direction of the perforated mirror204. 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 stop203limits the light flux emitted by the measurement light source201. The lens202performs primary image formation of the light in front of the lens205. The resultant light is then transmitted through the lens205and the dichroic mirror206to 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 lens205again through the pupil center. The incident light flux is transmitted through the lens205and then reflected by the periphery of the perforated mirror204.

The reflected light flux is separated by the conical light flux spectral prism208using the Gullstrand's principle through the stop207provided 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 sensor210. 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 unit301(to be described later with reference toFIG. 4) allows the diffusing plate222to 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 inFIG. 2, the stop207is 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 stops207aand207bof the stop207in accordance with the size of the cornea Ec (or the pupil Ep) of the eye E.

The stops207aand207bhave apertures with orbicular zone shapes. Inner diameters d1of these stops are the same. The outer diameters of the stops are expressed as d2>d3. In general, the apparatus performs measurement while the stop207ais inserted in the optical path02. If, however, the pupil Ep of the eye E is small in size and the outer diameter d2of an image formed on the pupil Ep has a size d2′ expressed as d2′>size of pupil Ep, the ring image on the image sensor210changes in brightness and size. This leads to incorrect measurement. In such a case, the apparatus performs measurement upon making a stop insertion/removal unit302(to be described later with reference toFIG. 4) switch from the stop207ato the stop207b.

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 mirror206. A lens211, a dichroic mirror212, a lens213, a folding mirror214, a lens215, a fixation target216, and a fixation target illumination light source217are sequentially arranged on an optical path03of 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 source217illuminates the fixation target216from its rear side and is projected on the fundus Er of the eye E through the lens215, the folding mirror214, the lens213, the dichroic mirror212, and the lens211. Note that a fixation induction motor224can move the lens215in the optical axis direction to implement a fogging state by performing diopter induction of the eye E.

An alignment prism stop223to be inserted/removed by an alignment prism stop insertion/removal unit303(to be described with reference toFIG. 4), a lens218, a kerato stop503for kerato measurement which is detachably inserted/removed in/from the optical path by a kerato stop insertion/removal unit304(to be described later with reference toFIG. 4), and an image sensor220are sequentially arranged on an optical path04in the reflecting direction of the dichroic mirror212.

Inserting/removing the alignment prism stop223allows performance of alignment when the alignment prism stop223is located on the optical path04and performance of anterior ocular segment observation or transillumination observation when the alignment prism stop223is removed from the optical path. Anterior ocular segment illumination light sources221aand221b, each having a wavelength of about 780 nm, are arranged diagonally forward of the eye E.

The shape of the alignment prism stop223will be described with reference toFIG. 3. A disc-like stop plate of the alignment prism stop223is provided with three aperture portions223a,223b, and223cfor the restriction of light fluxes. Alignment prisms301aand301bwhich transmit only light fluxes near a wavelength of 880 nm are respectively bonded to the aperture portions223aand223bon the two sides which are located on the dichroic mirror212side.

The kerato stop503is a stop for corneal shape measurement. The kerato stop insertion/removal unit304inserts the kerato stop503in the optical path when the apparatus measures the curvature radius of the cornea Ec of the eye E. The kerato stop503is 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 source290, 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 source290slightly deviates from a set value. This makes the size of the ring image captured by the image sensor220remain the same regardless of whether the operating distance slightly deviates, and hence can obtain an accurate curvature radius value (kerato value).

FIG. 5shows an example of an observation image displayed on an LCD monitor403(to be described later with reference toFIG. 4). Anterior ocular segment image light fluxes from the eye E illuminated by the anterior ocular segment illumination light sources221aand221bare formed into images on the light receiving sensor surface of the image sensor220through the dichroic mirror206, the lens211, the dichroic mirror212, and the central aperture portion223cof the alignment prism stop223.

The ocular refractive power measurement light source201also serves as a light source for alignment detection. At the time of alignment, the diffusing plate insertion/removal unit301inserts the translucent diffusing plate222in the optical path01. The insertion position of the diffusing plate222almost coincides with the primary image formation position of the projection lens202of the measurement light source201described above and also coincides with the focal position of the lens205. This temporarily forms light from the measurement light source201into an image on the diffusing plate222. This image then serves as a secondary light source and is projected as a thick parallel light flux propagating from the lens205to the eye E.

The cornea Ec of the eye E reflects this parallel light flux to form a bright spot image. The dichroic mirror206partly reflects this light flux again. The light fluxes is reflected by the dichroic mirror212through the lens211, and is transmitted through the aperture portions223a,223b, and223cof the alignment prism stop223and the alignment prisms301aand301b. The lens218focuses the light fluxes to form images Ta, Tb, and Tc on the image sensor220.

The central aperture portion223cof the alignment prism stop223is designed to transmit light fluxes having a wavelength of 780 nm or more from the anterior ocular segment illumination light sources221aand221b. The reflected light fluxes of the anterior ocular segment images illuminated by the anterior ocular segment illumination light sources221aand221bpropagate along same path in the observation optical system as that of the reflected light fluxes from the cornea Ec. The imaging lens218then forms these reflected light fluxes into images221a′ and221b′ on the image sensor220through the aperture portion223cof the alignment prism stop223. It is possible to align the eye E based on the positional relationship between the respective light fluxes obtained through these stops.

Referring toFIG. 1, a mask501provided on an optical path05and a light source502which is located near the diffusing plate and illuminates the mask501constitute a temperature-compensation optical system on the transmission side of the optical path04relative to the dichroic mirror206. As indicated by “707” inFIG. 7, the mask501has 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 path05.

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 sensor220. 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 source502before kerato measurement and performs imaging by using the image sensor220while a kerato stop503is inserted in the optical path. The apparatus compares the intervals between the four aperture portions of the mask501, 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. 4is a block diagram of the ophthalmic apparatus. The ophthalmic apparatus includes a control unit401, a light source driving circuit402, the LCD monitor403, a storage unit404, a memory405, the diffusing plate insertion/removal unit301, the stop insertion/removal unit302, the alignment prism stop insertion/removal unit303, the kerato stop insertion/removal unit304, a notification unit305, and a temporal change storage unit306.

The control unit401controls 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 circuit402controls ON/OFF operation or change in light amount for the measurement light source201, the anterior ocular segment illumination light source221a, the anterior ocular segment illumination light source221b, the fixation target illumination light source217, the kerato measurement light source290, and the light source502in accordance with commands from the control unit401. The LCD monitor403displays the anterior ocular segment image captured by the image sensor220, measurement values, and the like under the control of the control unit401which functions as a display control unit. The storage unit404stores 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 plate222, the stop207, the alignment prism stop223, the kerato stop503, and the like) which are inserted/removed in/from optical paths (to be described later). The memory405stores the anterior ocular segment image of the eye E captured by the image sensor220. 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 memory405. The anterior ocular segment image of the eye E captured by the image sensor220is combined with character data and graphic data. The LCD monitor403then displays the combined anterior ocular segment image, measurement values, and the like. The memory405stores the ocular refractive power calculation ring image captured by the image sensor210.

The diffusing plate insertion/removal unit301, the stop insertion/removal unit302, the alignment prism stop insertion/removal unit303, and the kerato stop insertion/removal unit304perform inserting/removing operation for the respective insertion/removal targets under the control of the control unit401. The diffusing plate insertion/removal unit301functions as an optical member insertion/removal unit, and inserts/removes the diffusing plate222in/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 unit302functions as an optical member insertion/removal unit, and inserts/removes the stops207aand207bof the stop207in/from the optical path upon switching between them. The alignment prism stop insertion/removal unit303functions as an optical member insertion/removal unit and inserts/removes the alignment prism stop223in/from the optical path. The alignment prism stop insertion/removal unit303functions as an optical member insertion/removal unit, and inserts/removes the kerato stop503for kerato measurement in/from the optical path. The notification unit305has 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 unit401. The notification unit305may perform notification by sound or displaying an insertion/removal check result on the LCD monitor403. Alternatively, the notification unit305may be configured to notify the examiner of normal operation instead of an abnormality. That is, the notification unit305may 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 unit306stores 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 unit401reads out the corresponding temporal change information from the temporal change storage unit306, and outputs a display form indicating the temporal change via the LCD monitor403or a separately provided output terminal.

A processing procedure at the time of the inserting/removing operation for each of the diffusing plate222, the stop207, the alignment prism stop223, and the kerato stop503will be described below with reference to the flowchart ofFIG. 6. When the examiner turns on the power supply of the ophthalmic apparatus before the processing, the control unit401performs an operation check on each driving unit.

First Embodiment

Detection of Inserting/Removing Operation for Diffusing Plate222with Respect to Optical Path

The first embodiment will be described below with reference toFIG. 6, in which inserting/removing operation for the diffusing plate222as an example of an optical member with respect to the optical path is detected.

(Processing to be Performed when Diffusing Plate222is Removed from Optical Path)

A processing procedure at the time of the removal of the diffusing plate222will be described with reference to the flowchart ofFIG. 6. In step S601, the control unit401controls the light source driving circuit402to turn on the measurement light source201to emit a predetermined amount of light, and controls the stop insertion/removal unit302to insert the stop207ain the optical path. The control unit401then controls the diffusing plate insertion/removal unit301to remove the diffusing plate222out of the optical path.

In step S602, the image sensor210performs imaging in synchronism with the removal of the diffusing plate222. The memory405stores a captured image. The image obtained in this case depicts nothing as indicated by “701” inFIG. 7because measurement light is transmitted through the lens205and emerges out of the ophthalmic apparatus and hence no reflected light reaches the image sensor210.

In step S603, the control unit401reads out a predetermined value at the time of the removal of the diffusing plate222from the storage unit404. 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 unit401compares the image analysis result obtained in step S602with the predetermined value read out in step S603to determine, based on the comparison result, whether the operation (the removing operation for the diffusing plate222) 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 unit401determines that the operation result is abnormal (NO in step S604), the process advances to step S606.

In step S605, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S606, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal. With the above operation, each process in the flowchart ofFIG. 6is complete.

(Processing to be Performed when Diffusing Plate222is Inserted in Optical Path)

A processing procedure at the time of the insertion of the diffusing plate222will be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S611to S615. In step S611, the control unit401controls the light source driving circuit402to turn on the measurement light source201to emit a predetermined amount of light, and controls the stop insertion/removal unit302to insert the stop207ain the optical path. The control unit401then controls the diffusing plate insertion/removal unit301to insert the diffusing plate222in the optical path.

In step S612, the image sensor210performs imaging in synchronism with the insertion of the diffusing plate222. The memory405stores a captured image. If the diffusing plate222is correctly inserted in the optical path, the light flux emitted by the measurement light source201is diffused by the diffusing plate222. The diffusing plate222then serves as a diffusing light source. The reflected light from this light source is transmitted through the perforated mirror204, the stop207(assume that the stop207ais inserted in the optical path), the light flux spectral prism208, and the lens209to be captured by the image sensor210. The image obtained in this case has a ring-like shape as indicated by “702” inFIG. 7. Since the stop207has 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 unit401reads out a predetermined value at the time of the insertion of the diffusing plate222from the storage unit404. Since the position of the diffusing plate222on the optical axis is determined in advance, the size or luminance of the ring image to be captured when the diffusing plate222is 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 unit401compares the image analysis result obtained in step S612with the predetermined value read out in step S613to determine, based on the comparison result, whether the operation (the inserting operation for the diffusing plate222) has been normally performed. The control unit401compares the analyzed diameter or luminance distribution with the diameter or luminance distribution stored in the storage unit404. If the comparison result falls within a predetermined range, it is possible to determine that the operation has been normally performed. If the control unit401determines that the operation result is normal (YES in step S614), the process advances to step S615. If the control unit401determines that the operation result is abnormal (NO in step S614), the process advances to step S616.

In step S615, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S616, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

Second Embodiment

Detection of Inserting/Removing Operation for Stop207with Respect to Optical Path

The second embodiment will be described below with reference toFIG. 6, in which inserting/removing operation for the stop207as an example of an optical member with respect to the optical path is detected.

(Processing to be Performed when Stop207ais Inserted in Optical Path)

A processing procedure at the time of the insertion of the stop207awill be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S801to S805. In step S801, the control unit401controls the light source driving circuit402to turn on the measurement light source201to emit a predetermined amount of light, and controls the diffusing plate insertion/removal unit301to remove the diffusing plate222from the optical path. The control unit401then controls the stop insertion/removal unit302to insert the stop207ain the optical path. Note that the control unit401may detect that the stop207bis removed from the optical path.

In step S802, the image sensor210performs imaging in synchronism with the insertion of the stop207a. The memory405stores a captured image. The image obtained in this case has a ring-like shape as indicated by “702” inFIG. 7. Since the stop207has 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 unit401reads out a predetermined value at the time of the insertion of the stop207afrom the storage unit404. The luminance value or the like of the acquired image is set as the predetermined value at the time of insertion. The stops207aand207bhave 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 unit302, and the stop207ais not completely inserted or removed in or from the optical path. In this case, as indicated by “708” inFIG. 7, since the shadows of the holding portions k of the stop207aon 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 plate222is inserted at a position deviating from the focal position of the lens205, 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 unit401compares the image analysis result obtained in step S802with the predetermined value read out in step S803to determine, based on the comparison result, whether the operation (the inserting operation for the stop207a) 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 unit401determines that the operation result is normal (YES in step S804), the process advances to step S805. If the control unit401determines that the operation result is abnormal (NO in step S804), the process advances to step S806.

In step S805, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S806, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

(Processing to be Performed when Stop207bis Inserted in Optical Path)

A processing procedure at the time of the insertion of the stop207bwill be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S811to S815. In step S811, the control unit401controls the light source driving circuit402to turn on the measurement light source201to emit a predetermined amount of light, and controls the diffusing plate insertion/removal unit301to remove the diffusing plate222from the optical path. The control unit401then controls the stop insertion/removal unit302to switch from the stop207ato the stop207bhaving a smaller outer diameter and insert the stop207bin the optical path. Note that the control unit401may detect that the stop207ais removed from the optical path.

In step S812, the image sensor210performs imaging in synchronism with the insertion of the stop207b. The memory405stores a captured image. The image obtained in this case has a ring-like shape as indicated by “703” inFIG. 7. Since the stop207bhas 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 stop207bis smaller in aperture area than the stop207a, the luminance of the ring image is lower than that of the ring image indicated by “702”.

In step S813, the control unit401reads out a predetermined value at the time of the insertion of the stop207bfrom the storage unit404. 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 stop207a. In step S814, the control unit401compares the image analysis result obtained in step S812with the predetermined value read out in step S813to determine, based on the comparison result, whether the operation (the inserting operation for the stop207b) 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 unit401determines that the operation result is normal (YES in step S814), the process advances to step S815. If the control unit401determines that the operation result is abnormal (NO in step S814), the process advances to step S816.

In step S815, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S816, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

Note that the above operation detection processing for the stop207may be performed following the operation detection processing for the diffusing plate222. 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 Stop223with Respect to Optical Path

The third embodiment will be described below with reference toFIG. 6, in which inserting/removing operation for the alignment prism stop223as an example of an optical member with respect to the optical path is detected.

(Processing to be Performed when Alignment Prism Stop223is Removed from Optical Path)

A processing procedure at the time of the removal of the alignment prism stop223will be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S901to S905. In step S901, the control unit401controls the light source driving circuit402to turn off the measurement light source201and the kerato measurement light source290and turn on the light source502. The control unit401also controls the kerato stop insertion/removal unit304to insert the kerato stop503in the optical path. In addition, the control unit401controls the alignment prism stop insertion/removal unit303to remove the alignment prism stop223from the optical path. Note that the position of the diffusing plate222is arbitrary.

In step S902, the image sensor220images the mask501of the temperature-compensation optical system in synchronism with the removal of the alignment prism stop223. The memory405stores a captured image. The image obtained in this case clearly depicts the four aperture portions of the mask501as indicated by “704” inFIG. 7.

In step S903, the control unit401reads out a predetermined value at the time of the removal of the alignment prism stop223from the storage unit404. 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 unit401compares the image analysis result obtained in step S902with the predetermined value read out in step S903to determine, based on the comparison result, whether the operation (the removing operation for the alignment prism stop223) 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 stop223has 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 unit401determines that the operation result is normal (YES in step S904), the process advances to step S905. If the control unit401determines that the operation result is abnormal (NO in step S904), the process advances to step S906.

In step S905, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S906, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

(Processing to be Performed when Alignment Prism Stop223is Inserted in Optical Path)

A processing procedure at the time of the insertion of the alignment prism stop223will be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S911to S915. In step S911, the control unit401controls the light source driving circuit402to turn off the measurement light source201and the kerato measurement light source290and turn on the light source502. The control unit401also controls the kerato stop insertion/removal unit304to insert the kerato stop503in the optical path. The control unit401also controls the alignment prism stop insertion/removal unit303to insert the alignment prism stop223from the optical path. Note that the position of the diffusing plate222is arbitrary.

In step S912, the image sensor220performs imaging in synchronism with the insertion of the alignment prism stop223. The memory405stores a captured image. The three stops of the aperture portions223a,223b, and223cof the alignment prism stop223receive light fluxes. Since the alignment prisms301aand301bare respectively bonded to the aperture portions223aand223b, the light fluxes passing through the aperture portions223aand223bare separated to the right and left. For this reason, the image obtained in this case depicts the four aperture portions of the mask501with each being separated into three portions, as indicated by705inFIG. 7.

In step S913, the control unit401reads out a predetermined value at the time of the insertion of the alignment prism stop223from the storage unit404. 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 portion223cof the alignment prism stop223, 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 unit401compares the image analysis result obtained in step S912with the predetermined value read out in step S913to determine, based on the comparison result, whether the operation (the inserting operation for the alignment prism stop223) 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 unit401determines that the operation result is normal (YES in step S914), the process advances to step S915. If the control unit401determines that the operation result is abnormal (NO in step S914), the process advances to step S916.

In step S915, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S916, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

Note that the control unit401may be configured to check insertion/removal by comparing the image captured in step S902with the image captured in step S912and performing determination operation by determining the normal/abnormal operation of the alignment prism stop223based on the number of aperture portion images detected or a luminance value difference.

Fourth Embodiment

Detection of Inserting/Removing Operation for Kerato Stop503with Respect to Optical Path

The fourth embodiment will be described below with reference toFIG. 6, in which inserting/removing operation for the kerato stop503as an example of an optical member with respect to the optical path is detected.

(Processing to be Performed when Kerato Stop503is Inserted in Optical Path)

A processing procedure at the time of the insertion of the kerato stop503will be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S1101to S1105. In step S1101, the control unit401controls the light source driving circuit402to turn off the measurement light source201and the kerato measurement light source290and turn on the light source502. The control unit401also controls the alignment prism stop insertion/removal unit303to remove the alignment prism stop223from the optical path. Note that the position of the diffusing plate222is arbitrary. In addition, the control unit401controls the kerato stop insertion/removal unit304to insert the kerato stop503in the optical path. In step S1102, the image sensor220images the mask501of the temperature-compensation optical system in synchronism with the insertion of the kerato stop503. The memory405stores a captured image. The image obtained in this case is the same as that obtained in step S902. If, therefore, the processing in step S902has already been performed, the corresponding image may also be used in this processing. That is, the processing in step S1102may be omitted.

In step S1103, the control unit401reads out a predetermined value at the time of the insertion of the kerato stop503from the storage unit404. 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 unit401compares the image analysis result obtained in step S1102with the predetermined value read out in step S1103to determine, based on the comparison result, whether the operation (the inserting operation for the kerato stop503) 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 unit401determines that the operation result is normal (YES in step S1104), the process advances to step S1105. If the control unit401determines that the operation result is abnormal (NO in step S1104), the process advances to step S1106.

In step S1105, the control unit401stores the current image analysis result in the temporal change storage unit306. In step S1106, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

(Processing to be Performed when Kerato Stop503is Removed from Optical Path)

A processing procedure at the time of the removal of the kerato stop503will be described next, with the operations in steps S601to S605in the flowchart ofFIG. 6being replaced with those in steps S1111to S1115. In step S1111, the control unit401controls the light source driving circuit402to turn off the measurement light source201and the kerato measurement light source290and turn on the light source502. The control unit401also controls the alignment prism stop insertion/removal unit303to remove the alignment prism stop223from the optical path. Note that the position of the diffusing plate222is arbitrary. In addition, the control unit401controls the kerato stop insertion/removal unit304to remove the kerato stop503from the optical path.

In step S1112, the image sensor220images the mask501of the temperature-compensation optical system in synchronism with the removal of the kerato stop503. The memory405stores 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” inFIG. 7, as indicated by706inFIG. 7. Larger aperture images are observed from this image for the following reason. The pupil diameter has increased upon removal of the alignment prism stop223from the optical path, and the light amount has increased to increase the luminance value.

In step S1113, the control unit401reads out a predetermined value at the time of the removal of the kerato stop503from the storage unit404. 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 unit401compares the image analysis result obtained in step S1112with the predetermined value read out in step S1113to determine, based on the comparison result, whether the operation (the removing operation for the kerato stop503) 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 unit401determines that the operation result is normal (YES in step S1114), the process advances to step S1115. If the control unit401determines that the operation result is abnormal (NO in step S1114), the process advances to step S1116.

In step S1115, the control unit401stores the current image analysis result in the temporal change storage unit306as the second storage unit. In step S1116, the control unit401controls the notification unit305to notify the examiner that the operation is abnormal.

Note that the control unit401may be configured to check insertion/removal by comparing the image captured in step S1102with the image captured in step S1112and performing determination operation by determining the normal/abnormal operation of the kerato stop503based 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 (stops207aand207b) 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 stop223with respect to the optical path and detection of inserting/removing operation for the kerato stop503with 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

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.