ophthalmic devices

Abstract

The present invention provides an ophthalmic device that can expand the detection range of the eye under examination in the direction along the principal optical axis of the optical head with a simple configuration. [Solution] The ophthalmic apparatus 1 comprises an optical head 5, one or more parallel light projection units 30A to 30C that project parallel light onto the eye E under examination, and an observation system 12 having an objective lens 12a and an image sensor 12g. The range in the direction along the principal optical axis of the optical head 5, where a bright spot image is captured by the image sensor 12g, includes at least an area outside a predetermined range based on a position that is the working distance of the objective lens 12a from the eye E under examination.

Description

Technical Field

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[0003]

[0001] The present invention relates to an ophthalmic device equipped with an optical head.

Background Art

[0002] In ophthalmology, various eye characteristics such as the refractive power of the eye to be examined, the corneal shape, the intraocular pressure, and the number of corneal endothelial cells are acquired (measured, photographed, observed, etc.) using an ophthalmic device. Before acquiring the eye characteristics of the eye to be examined by this ophthalmic device, alignment of the optical head of the ophthalmic device with respect to the eye to be examined is performed. This alignment of the optical head includes Z alignment, which is alignment in the direction along the principal optical axis of the optical head (operating distance direction), and XY alignment, which is alignment in two directions perpendicular to this direction. When performing Z alignment, the Z-direction distance between the eye to be examined and the optical head is measured, and based on this measurement result, the position adjustment of the optical head in the Z direction is performed.

[0003] For example, the ophthalmic device described in Patent Document 1 is an auto-refractokeratometer, and a pair of parallel light projection units that emit parallel light and a keratometry light source that emits keratometry light are provided on the front surface of its optical head. This ophthalmic device projects the parallel light emitted from the pair of parallel light projection units and the keratometry light emitted from the keratometry light source obliquely onto the anterior eye segment of the eye to be examined, and photographs the anterior eye segment image of this anterior eye segment through an objective lens having a principal optical axis. Then, the ophthalmic device measures the Z-direction distance between the eye to be examined and the optical head based on the ratio between the interval of the bright spots corresponding to the pair of parallel lights in the anterior eye segment image and the interval of the keratometry image in the anterior eye segment image, and performs Z alignment of the optical head based on this measurement result.

[0004] In addition, the ophthalmic device (auto-refractokeratometer) described in Patent Document 2 separately provides a Z alignment system of the lever type to the optical head, measures the Z-direction distance between the eye to be examined and the optical head, and performs Z alignment of the optical head based on this measurement result.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-127648 [Patent Document 2] Japanese Patent Publication No. 2024-60915 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the ophthalmic apparatus described in Patent Document 1, the irradiation range of parallel light from a pair of parallel light projection units to the eye under examination depends on the lens diameter of the parallel light projection units. Therefore, the Z-direction position range of the optical head capable of measuring distance in the Z-direction, in other words, the detection range of the eye under examination in the Z-direction of the optical head, is limited. For this reason, depending on the Z-direction positional relationship between the eye under examination and the optical head at the start of alignment, Z-alignment may not be possible.

[0007] In the ophthalmic device described in Patent Document 2, a separate optical lever-type Z-alignment system must be provided on the optical head in order to perform Z-alignment, which leads to problems of increased cost and larger device size.

[0008] This invention has been made in view of these circumstances, and aims to provide an ophthalmic device that can expand the detection range of the eye under examination in the direction along the principal optical axis of the optical head with a simple configuration. [Means for solving the problem]

[0009] An ophthalmic apparatus for achieving the object of the present invention comprises an optical head, one or more parallel light projection units provided on the optical head for projecting parallel light onto the eye under examination, and an observation system having an objective lens and an image sensor, wherein when reflected parallel light projected onto the eye under examination enters the image sensor through the objective lens, the image sensor captures a bright spot image of the reflected light, wherein the range in the direction along the principal optical axis of the optical head from which the bright spot image is captured by the image sensor includes at least a range outside a predetermined range based on a position that is a distance from the eye under examination equal to the working distance of the objective lens. [Effects of the Invention]

[0010] This invention allows for an expansion of the detection range of the eye under examination in the direction along the principal optical axis of the optical head with a simple configuration. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view of the ophthalmic device according to the first embodiment. [Figure 2] This is a diagram showing the configuration of the optical head. [Figure 3] Figure IIIA shows the relationship between the Z-direction distance between the optical head and the eye under examination and the size of the bright spot image, and figure IIIB shows the relationship between this Z-direction distance and the size of the keratling image. [Figure 4] This is a perspective view of the keratin plate and parallel light projection unit (13A) located on the front of the optical head. [Figure 5] This is a front view of the keratin plate and parallel light projection unit (13A) located on the front of the optical head. [Figure 6] This diagram illustrates the Z-direction position range of the optical head that satisfies the imaging conditions corresponding to the two parallel light projection units (13A). [Figure 7] This diagram illustrates the Z-direction position range of the optical head that satisfies the imaging conditions corresponding to the parallel light projection unit (13B). [Figure 8] This diagram illustrates the Z-direction position range of the optical head that satisfies the imaging conditions corresponding to the parallel light projection unit (13C). [Figure 9] It is a functional block diagram of a control device. [Figure 10] It is an explanatory diagram for explaining an example of a method for calculating the Z-direction distance between an optical head and an eye to be examined based on a captured image. [Figure 11] It is a flowchart showing the measurement process of the eye characteristics of an eye to be examined, particularly the flow of Z-alignment processing, by the ophthalmic device of the first embodiment. [Figure 12] It is an explanatory diagram for explaining the parallel light projection units (13B, 13C) of the ophthalmic device of the second embodiment. [Figure 13] It is an explanatory diagram for explaining the parallel light projection unit (13D) of the ophthalmic device of the third embodiment. [Figure 14] It is an explanatory diagram for explaining a modified example of the parallel light projection unit (13D) of the ophthalmic device of the third embodiment. [Figure 15] It is an explanatory diagram for explaining a modified example of the parallel light projection unit (13D) of the ophthalmic device of the third embodiment. [Figure 16] It is a perspective view of the front surface of the optical head of the ophthalmic device of the fourth embodiment. [Figure 17] It is a front view of the front surface of the optical head of the ophthalmic device of the fourth embodiment. [Figure 18] It is a diagram showing a modified example of an observation system. [Figure 19] It is an explanatory diagram for explaining the calculation of the Z-direction distance between an eye to be examined and an optical head based on a captured image obtained when there is one parallel light projection unit (13A).

Embodiments for Carrying Out the Invention

[0012] [First Embodiment] FIG. 1 is a side view of the ophthalmic device 1 of the first embodiment. Among the XYZ directions (three directions) orthogonal to each other in the figure, the Y direction is the vertical direction, the Z direction is the front-back direction parallel to the front direction approaching the eye to be examined E (subject) and the back direction moving away from the subject (also referred to as the operating distance direction), and the X direction is the left-right direction perpendicular to both the vertical direction and the front-back direction.

[0013] <Overall configuration of ophthalmic device 1> The ophthalmic device 1 is an autorefractometer / keratometer capable of measuring the refractive power and corneal shape of the eye E being examined as ocular characteristics. This ophthalmic device 1 comprises a base 2, a face support unit 3, a drive mechanism 4, an optical head 5 (also called a measuring head or device body), and a display unit 6.

[0014] The drive mechanism 4 is composed of an actuator (not shown), such as a motor. This drive mechanism 4 moves the optical head 5 in the XYZ directions relative to the base 2. This allows the optical head 5 to be moved relative to the eye under examination E in the XYZ directions, thus enabling XYZ alignment of the optical head 5 with respect to the eye under examination E.

[0015] The optical head 5 has a function for measuring the ocular characteristics (refractive power and corneal shape) of the eye E under examination. A display unit 6 is attached to the optical head 5. The optical head 5 also contains various optical systems (including an image sensor, various light sources, and various drive units) corresponding to the observation of the eye E under examination, the XYZ alignment of the optical head 5 with respect to the eye E under examination, and the measurement of refractive power and corneal shape, as well as a control device 9 (see Figure 2).

[0016] The display unit 6 may be, for example, a touch panel monitor. The display unit 6 is rotatably held by the optical head 5, and its position and orientation can be manually adjusted. The display unit 6 displays the observed image of the eye E acquired by the optical head 5, the measurement results of ocular characteristics such as refractive power and corneal shape of the eye E, a setting menu screen for making various settings, and an operation menu screen for making various operations.

[0017] The display surface of the display unit 6 accepts input operations by the examiner via touch, and therefore functions as an operating unit. Note that the ophthalmic device 1 may also be equipped with other known operating units besides the display unit 6.

[0018] <Configuration of Optical Head 5> Figure 2 shows the configuration of the optical head 5. As shown in Figure 2, the optical head 5 includes an observation system 12, a parallel light projection system 13, an XY alignment system 14, a target projection system 15, a measurement pattern projection system 16, and a light receiving system 17.

[0019] Observation system 12 is used for observing the anterior segment of the eye E under examination, and for photographing this anterior segment. Observation system 12 is an object-side telecentric optical system including an objective lens 12a having a principal optical axis O1 parallel to the Z direction. In this observation system 12, the following components are arranged in order from the eye E side along the principal optical axis O1: objective lens 12a, dichroic filter 12b, half mirror 12c, relay lens 12d, dichroic filter 12e, imaging lens 12f, and a CMOS (complementary metal oxide semiconductor) or CCD (Charge Coupled Device) type image sensor 12g. Observation system 12 also has an illumination light source (not shown). Since each component of observation system 12 is based on publicly known technology, a detailed explanation thereof is omitted.

[0020] The illumination light emitted from the illumination light source of the observation system 12 illuminates the anterior segment of the eye E under examination and is reflected from the anterior segment. This reflected light enters the objective lens 12a, passes through various parts of the observation system 12, and enters the imaging surface of the image sensor 12g. As a result, the reflected light is imaged by the image sensor 12g, and the image sensor 12g acquires an observation image (image data) of the anterior segment of the eye E under examination. The image sensor 12g outputs the observation image to the control device 9.

[0021] A keratin plate 12h and a keratin light source 12i are provided around the objective lens 12a, which are used to measure the corneal shape of the cornea Ec of the eye E under examination. The keratin plate 12h and the keratin light source 12i project a single or multiple (double in this embodiment) ring-shaped light beam onto the cornea Ec. The keratin light source 12i is a finite-distance illumination light source of the present invention that illuminates the eye E under examination from a finite distance. The ring-shaped light beam reflected by the cornea Ec enters the imaging surface of the image sensor 12g via the objective lens 12a and the dichroic filter 12b, etc. As a result, a keratin image 32 (see Figure 6) is captured by the image sensor 12g. The image sensor 12g outputs the keratin image 32 (image data) to the control device 9.

[0022] The parallel light projection system 13 is part of the configuration necessary for detecting the alignment state of the optical head 5 in the Z direction (direction along the principal optical axis O1) relative to the eye E under examination, and projects parallel light onto the eye E under examination. The detection of the alignment state here includes detecting the position of the optical head 5 in the Z direction and detecting the distance in the Z direction between the eye E under examination and the optical head 5. The parallel light projection system 13 includes two parallel light projection units 13A and parallel light projection units 13B and 13C.

[0023] Each parallel light projection unit 13A to 13C has a light source 130 and a projection lens 131. Each light source 130 emits a light beam toward the projection lens 131. The light beam emitted from each light source 130 is converted into parallel light (collimated light) by each projection lens 131. Therefore, each parallel light projection unit 13A to 13C performs infinite distance illumination by emitting parallel light. The parallel light emitted from each parallel light projection unit 13A to 13C is projected obliquely onto the cornea Ec of the eye E under examination and reflected by the cornea Ec.

[0024] The reflected parallel light reflected by the cornea Ec enters the objective lens 12a of the optical head 5 along the principal optical axis O1 when the Z-direction position of the optical head 5 relative to the eye E of the eye under examination satisfies predetermined conditions (set for each parallel light projection unit 13A to 13C), and then enters the imaging surface of the image sensor 12g via the objective lens 12a and the dichroic filter 12b, etc. As a result, along with the keratling image 32 (see Figure 6), two bright spot images 30A (see Figure 6) corresponding to the reflected parallel light projected by the two parallel light projection units 13A are captured by the image sensor 12g, or one bright spot image 30B, 30C (see Figures 7 and 8) corresponding to the reflected parallel light projected by either the parallel light projection unit 13B or 13C is captured by the image sensor 12g.

[0025] In Figure 3, the symbol IIIA shows the relationship between the Z-direction distance between the optical head 5 and the eye under examination E (the Z-direction position of the eye under examination E in the figure) and the size of the bright spot images 30A to 30C, while the symbol IIIB shows the relationship between this Z-direction distance and the size of the keratling image 32. The symbol 12j in the figure represents the aperture, which is positioned at the focal length of the objective lens 12a.

[0026] As shown by the symbol IIIA in Figure 3, when parallel light is projected onto the eye E from each parallel light projection unit 13A to 13C, which are infinite-distance illumination sources, and the reflected light is captured by the image sensor 12g of the observation system 12, which is an object-side telecentric optical system, the size of the bright spot images 30A to 30C remains approximately constant even when the Z-direction distance between the eye E and the optical head 5 changes. On the other hand, as shown by the symbol IIIB in Figure 3, when a ring-shaped beam of light is projected onto the eye E from a finite-distance illumination source keratling light source 12i, and the reflected light is captured by the image sensor 12g of the observation system 12, the size of the keratling image 32 changes according to the Z-direction distance between the eye E and the optical head 5.

[0027] Returning to Figure 2, when the optical head 5 is performing Z-alignment, the image sensor 12g outputs an image 34 (image data) containing at least one of the bright spot images 30A to 30C and the keratin image 32 to the control device 9 (see Figure 7). Then, as will be described in more detail later, the control device 9 calculates the distance in the Z direction between the eye E under examination and the optical head 5 based on this image 34, and performs Z-alignment by moving the optical head 5 in the Z direction based on this calculation result.

[0028] The XY alignment system 14 is used to detect the alignment state of the optical head 5 in the X and Y directions relative to the eye E under examination. The XY alignment system 14 forms an optical path branched from the observation system 12 via a half mirror 12c. This XY alignment system 14 includes an alignment light source 14a and a projection lens 14b. The alignment light source 14a emits a light beam toward the projection lens 14b. The light beam emitted from the alignment light source 14a is converted into a parallel light beam by the projection lens 14b, reflected by the half mirror 12c, and projected onto the cornea Ec via a dichroic filter 12b and an objective lens 12a.

[0029] The light beam reflected by the cornea Ec enters the imaging surface of the image sensor 12g via the objective lens 12a and the dichroic filter 12b. As a result, a bright spot image for XY alignment is captured by the image sensor 12g, and the image sensor 12g outputs the captured image 34 (image data) of the bright spot image for XY alignment to the control device 9. This allows the display unit 6 to display the bright spot image for Y alignment. The control device 9 then drives the drive mechanism 4 based on the captured image 34 to adjust the position of the bright spot image in the X and Y directions, thereby performing XY alignment. Note that other known methods may be used for XY alignment.

[0030] The target projection system 15 fixes the line of sight of the eye E under examination and projects the light beam of the fixation target onto the fundus Ef of the eye E under examination in order to fixate or cloud the eye E under examination when objective measurement of the refractive power of the eye E under examination.

[0031] The target projection system 15 includes a target display unit 15a, a half mirror 15b, a relay lens 15c, a reflective mirror 15d, a focusing lens 15e (also called a moving lens), a relay lens 15f, a field lens 15g, a VCC lens 15h which is a variable cross cylinder lens, a reflective mirror 15i, dichroic filters 15j, 12b, and an objective lens 12a.

[0032] Furthermore, the target projection system 15 has an optical axis O2 parallel to the principal optical axis O1 described above, and the focusing lens 15e, relay lens 15f, field lens 15g, and VCC lens 15h are arranged on this optical axis O2.

[0033] The target display unit 15a may be any of the following display devices: a dot matrix liquid crystal display (LCD) or a matrix light-emitting diode (LED). This target display unit 15a displays a fixation target and emits the light beam of this target towards the half mirror 15b.

[0034] The light beam of the fixation target displayed on the target display unit 15a is reflected by the half mirror 15b, and then projected onto the eye under examination E via the relay lens 15c, the reflection mirror 15d, the focusing lens 15e, the relay lens 15f, the field lens 15g, the VCC lens 15h, the reflection mirror 15i, the dichroic filters 15j and 12b, and the objective lens 12a. This makes it possible to present the fixation target to the eye under examination E.

[0035] Furthermore, the target projection system 15 has a glare light source 15k used for glare testing of the eye E under examination. During the glare test, the glare light source 15k emits glare light to the half mirror 15b. As a result, the glare light is projected onto the eye E under examination via each part from the half mirror 15b to the objective lens 12a.

[0036] The focusing lens 15e is positioned to move back and forth along the optical axis O2 of the target projection system 15. The focusing lens 15e is moved back and forth along the optical axis O2 by the interlocking movement mechanism 27 described later. This allows the refractive power of the light beam of the fixation target to be changed, and thus the presentation distance of the fixation target to the eye under examination E can be changed. As a result, the eye under examination E can be made to fixate on or fogging the fixation target.

[0037] The VCC lens 15h has a pair of positive and negative cylindrical lenses. Each of the cylindrical lenses can rotate independently around the optical axis O2. The VCC lens 15h has the function of correcting (correcting) the cylindrical power (astigmatism power) and axial angle (astigmatism axis angle) among the aberrations caused by the refractive characteristics of the eye E being examined.

[0038] The measurement pattern projection system 16 projects a ring-shaped measurement pattern light beam (also called measurement light) onto the fundus Ef, which is used to measure the objective refractive power of the eye E under examination.

[0039] The measurement pattern projection system 16 includes a reflector measurement unit 16a, a relay lens 16b, an pupil ring 16c, a field lens 16d, a perforated prism 16e, a rotary prism 16f, a dichroic filter 15j, a dichroic filter 12b, and an objective lens 12a.

[0040] Furthermore, the measurement pattern projection system 16 has an optical axis O3 parallel to the principal optical axis O1 and optical axis O2 described above. A reflector measurement unit 16a, a relay lens 16b, an pupil ring 16c, a field lens 16d, and a perforated prism 16e are arranged on this optical axis O3.

[0041] The refractometer measurement unit 16a includes an LED light source 16h, a collimator lens 16i, a conical prism 16j, and a measurement pattern forming plate 16k. The LED light source 16h and the pupil ring 16c are positioned optically conjugate. The forming plate 16k and the fundus Ef are also positioned optically conjugate.

[0042] The reflector measurement unit 16a is positioned to move back and forth along the optical axis O3 of the measurement pattern projection system 16. The reflector measurement unit 16a is moved back and forth along the optical axis O3 by the interlocking movement mechanism 27, which will be described later.

[0043] The light beam emitted from the LED light source 16h is made into parallel light by the collimator lens 16i, and then emitted towards the relay lens 16b after passing through the conical prism 16j and the forming plate 16k. This light beam is projected onto the fundus Ef after passing through the relay lens 16b, pupil ring 16c, field lens 16d, the reflective surface of the perforated prism 16e, the rotary prism 16f, the dichroic filter 15j, the dichroic filter 12b, and the objective lens 12a. As a result, a ring-shaped measurement pattern of light beam is projected onto the fundus Ef. Note that the shape of this measurement pattern of light beam is distorted by the refractive power of the eye E under examination before being projected onto the fundus Ef.

[0044] The light-receiving system 17 receives the retinal reflected light of the measurement pattern projected onto the retinal Ef by the measurement pattern projection system 16. The light-receiving system 17 includes an objective lens 12a, dichroic filters 12b and 15j, a rotary prism 16f, a perforated prism 16e, a field lens 17a, a reflective mirror 17b, a relay lens 17c, a focusing lens 17d (also called a moving lens), a reflective mirror 17e, a dichroic filter 12e, an imaging lens 12f, and an image sensor 12g.

[0045] Furthermore, the light-receiving system 17 has an optical axis O4 parallel to the principal optical axis O1, optical axis O2, and optical axis O3 described above. A reflective mirror 17b, a relay lens 17c, a focusing lens 17d, and a reflective mirror 17e are arranged on this optical axis O4.

[0046] The focusing lens 17d is positioned to move back and forth along the optical axis O4 of the light-receiving system 17. The focusing lens 17d is moved back and forth along the optical axis O4 by the interlocking movement mechanism 27, which will be described later.

[0047] The retinal reflected light of the measurement pattern reflected by the retinal Ef enters the light-receiving surface of the image sensor 12g via the objective lens 12a, dichroic filters 12b, 15j, rotary prism 16f, perforated prism 16e, field lens 17a, reflective mirror 17b, relay lens 17c, focusing lens 17d (also called moving lens), reflective mirror 17e, dichroic filter 12e, and imaging lens 12f. The image sensor 12g captures the retinal reflected light and outputs a ring image (image data) to the control device 9.

[0048] The interlocking movement mechanism 27, although not shown in the diagram, includes a holding member that integrally holds (connects) the focusing lens 15e, the reflector measurement unit 16a, and the focusing lens 17d; a sliding mechanism that holds the holding member so that it can slide freely in a direction parallel to the principal optical axis O1 (each optical axis O2 to O4) (Z direction); and a drive mechanism such as a motor that moves the holding member forward and backward in the Z direction. As a result, the focusing lens 15e, the reflector measurement unit 16a, and the focusing lens 17d are moved in conjunction (integrally) along the Z direction by the interlocking movement mechanism 27.

[0049] <Parallel light projection units 13A~13C> Figure 4 is a perspective view of the keratin plate 12h and parallel light projection units 13A to 13C located on the front of the optical head 5. Figure 5 is a front view of the keratin plate 12h and parallel light projection units 13A to 13C located on the front of the optical head 5.

[0050] As shown in Figures 4 and 5, the two parallel light projection units 13A correspond to the first parallel light projection unit of the present invention and are provided on the kerat plate 12h. Specifically, when the kerat plate 12h is viewed from the front side in the Z direction (corresponding to one side of the principal optical axis O1), the two parallel light projection units 13A are provided at the intersections of a straight line L (see Figure 5) that is perpendicular to the principal optical axis O1 and parallel to the X direction, and the inner ring of the double-ring kerat ring light source 12i. For this reason, the two parallel light projection units 13A are provided at positions offset on both sides in the left-right direction (X direction) from the principal optical axis O1, and are in a point-symmetric positional relationship with respect to the principal optical axis O1. Note that the positions of the two parallel light projection units 13A are not limited to the positions shown in Figures 4 and 5 and can be changed as appropriate.

[0051] The parallel light projection units 13B and 13C correspond to the second parallel light projection unit of the present invention, and are located on the outer periphery of the kerat plate 12h (parallel light projection unit 13A) and on a straight line L when the kerat plate 12h is viewed from the front side in the Z direction. Specifically, the parallel light projection unit 13B (the near-field parallel light projection unit of the present invention) is located to the right of the parallel light projection unit 13A, which is located to the right of the principal optical axis O1, and the parallel light projection unit 13C (the far-field parallel light projection unit of the present invention) is located to the left of the parallel light projection unit 13A, which is located to the left of the principal optical axis O1.

[0052] Each parallel light projection unit 13A to 13C always projects parallel light onto the eye E (cornea Ec) under examination, regardless of the Z-direction position of the optical head 5. The Z-direction position range of the optical head 5 that satisfies the conditions (hereinafter simply abbreviated as "imaging conditions") for the reflected light of this parallel light to pass through the objective lens 12a along the principal optical axis O1 and be imaged by the image sensor 12g is set individually for each parallel light projection unit 13A to 13C.

[0053] Figure 6 is a diagram illustrating the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to the two parallel light projection units 13A. In Figure 6, the acquired images 34 (reference numerals 6D to 6H) obtained when the Z-direction position (Z-direction distance) of the optical head 5 relative to the eye E is changed, as shown by reference numerals 6A to 6C.

[0054] As indicated by the symbol IIIB in Figure 3 above, the size of the keratling image 32 changes according to the change in the Z-direction position of the optical head 5. However, in Figure 6, to avoid complexity in the drawing, the size of the keratling image 32 is shown as constant regardless of the Z-direction position of the optical head 5 (the same applies to Figures 7, 8, 12, and 13 described later). Also, in the upper part of Figure 6, the Z-direction position of the eye E is fixed and the Z-direction position of the eye under examination is changed, but in reality, the Z-direction position of the eye E is fixed and the Z-direction position of the optical head 5 is changed (the same applies to Figures 7, 8, 12, and 13 described later). Furthermore, the symbol "WD" in Figure 6 indicates the working distance position, which is a known working distance (WD) of the objective lens 12a from the optical head 5 (objective lens 12a).

[0055] As shown in Figure 6, the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to each parallel light projection unit 13A is a predetermined range such that the eye under examination E is positioned within the range between detection limit WD(near) and detection limit WD(far) with respect to the working distance position WD. This predetermined range corresponds to the predetermined range and first position range of the present invention. When the Z-direction position of the optical head 5 is within the predetermined range, that is, when the eye under examination E is positioned within the range between detection limit WD(near) and detection limit WD(far), two bright spot images 30A corresponding to the reflected parallel light projected by each parallel light projection unit 13A appear in the captured image 34.

[0056] The two bright spot images 30A in the captured image 34 will be in focus when the Z-direction position of the optical head 5 is adjusted within a predetermined range so that the eye under examination E is positioned at or near the working distance position WD (see reference numerals 6B and 6F in Figure 6).

[0057] When the Z-direction position of the optical head 5 approaches the eye E under examination within a predetermined range, the eye E approaches the optical head 5 relatively, and the position of the eye E approaches the detection limit WD(near) within the range RA1 between the working distance position WD and the detection limit WD(near). In this case, the two bright spot images 30A in the captured image 34 become defocused (see reference numeral 6G in Figure 6). Then, when the optical head 5 approaches the eye E under examination beyond the predetermined range, the eye E approaches the optical head 5 relatively to a position beyond the detection limit WD(near), as shown by reference numeral 6C in Figure 6, and the two bright spot images 30A in the captured image 34 disappear (see reference numeral 6H in Figure 6).

[0058] Conversely, when the Z-direction position of the optical head 5 moves away from the eye E within a predetermined range, the eye E moves relatively far away from the optical head 5, causing the position of the eye E to approach the detection limit WD(far) within the range RA2 between the working distance position WD and the detection limit WD(far). In this case as well, the two bright spot images 30A in the captured image 34 become defocused (see reference numeral 6E in Figure 6). Then, when the optical head 5 moves away from the eye E beyond the predetermined range, the eye E moves relatively far away from the optical head 5 to a position beyond the detection limit WD(far), as shown by reference numeral 6A in Figure 6, causing the two bright spot images 30A in the captured image 34 to disappear (see reference numeral 6D in Figure 6).

[0059] Furthermore, as indicated by the symbol IIIA in Figure 3 described above, when each parallel light projection unit 13A is an infinite illumination source and the observation system 12 is an object-side telecentric optical system, the distance between the two bright spot images 30A in the captured image 34 remains approximately constant even when the Z-direction position of the optical head 5 changes.

[0060] Figure 7 is a diagram illustrating the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to the parallel light projection unit 13B. In Figure 7, the acquired images 34 (reference numerals 7D to 7F) obtained when the Z-direction position (Z-direction distance) of the optical head 5 relative to the eye E under examination is changed, as shown by reference numerals 7A to 7C.

[0061] As shown in Figure 7, the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to the parallel light projection unit 13B (corresponding to the second position range of the present invention) is a position range (hereinafter referred to as the near range) in which the eye under examination E is positioned between detection limit B1 and detection limit B2 in the figure. This near range partially overlaps with the predetermined range, but includes a range closer to the eye under examination E than the predetermined range. Detection limit B1 is set to be closer to the optical head 5 than detection limit WD(near) in the Z direction. Detection limit B2 is set between detection limit WD(near) and working distance position WD in the Z direction. When the Z-direction position of the optical head 5 is within the near range, that is, when the eye under examination E is positioned within the range between detection limit B1 and detection limit B2, a bright spot image 30B corresponding to the reflected light of the parallel light projected by the parallel light projection unit 13B appears in the captured image 34.

[0062] When the Z-direction position of the optical head 5 is within a predetermined range excluding the overlapping range with the near range, the eye under examination E is positioned within the range RB1 between the working distance position WD and the detection limit B2, as shown by reference numeral 7A in Figure 7. In this case, as shown by reference numeral 7D in Figure 7, two bright spot images 30A appear in the captured image 34, but the bright spot image 30B disappears.

[0063] When the Z-direction position of the optical head 5 is within the overlapping range between the predetermined range and the near range, the eye under examination E is positioned within the range RB2 between the detection limit B2 and the detection limit WD(near), as shown by reference numeral 7B in Figure 7. In this case, two bright spot images 30A and one bright spot image 30B appear in a defocused state in the captured image 34, as shown by reference numeral 7E in Figure 7. This makes it possible to determine that the Z-direction position of the optical head 5 is within the overlapping range between the predetermined range and the near range.

[0064] When the Z-direction position of the optical head 5 is within the near range excluding the overlapping range with a predetermined range (hereinafter referred to as the "non-overlapping near range"), as shown by reference numeral 7C in Figure 7, the eye under examination E is positioned within the range RB3 between the detection limit WD (near) and the detection limit B1. In this case, as shown by reference numeral 7F in Figure 7, two bright spot images 30A disappear from the captured image 34, and only one bright spot image 30B remains in the captured image 34. This makes it possible to determine that the optical head 5 is located within the non-overlapping near range.

[0065] Figure 8 is a diagram illustrating the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to the parallel light projection unit 13C. Figure 8 shows the acquired images 34 (reference numerals 8D to 8F) obtained when the Z-direction position (Z-direction distance) of the optical head 5 relative to the eye E under examination is changed, as shown by reference numerals 8A to 8C.

[0066] As shown in Figure 8, the Z-direction position range of the optical head 5 that satisfies the imaging conditions corresponding to the parallel light projection unit 13C (corresponding to the second position range of the present invention) is a position range (hereinafter referred to as the far range) in which the eye under examination E is positioned between detection limit C1 and detection limit C2 in the figure. This far range partially overlaps with the predetermined range, but includes a range further from the eye under examination E than the predetermined range. Detection limit C1 is set to be further from the optical head 5 than detection limit WD(far) in the Z direction. Detection limit C2 is set between the working distance position WD and detection limit WD(far) in the Z direction. When the Z-direction position of the optical head 5 is within the far range, that is, when the eye under examination E is positioned within the range between detection limit C1 and detection limit C2, a bright spot image 30C corresponding to the reflected parallel light projected by the parallel light projection unit 13C appears in the captured image 34.

[0067] When the Z-direction position of the optical head 5 is within a predetermined range excluding the overlapping range with the far range, the eye under examination E is positioned within the range RC1 between the working distance position WD and the detection limit C2, as shown by reference numeral 8C in Figure 8. In this case, as shown by reference numeral 8F in Figure 8, two bright spot images 30A appear in the captured image 34, but the bright spot image 30C disappears.

[0068] When the Z-direction position of the optical head 5 is within the overlapping range between the predetermined range and the far range, the eye under examination E is positioned within the range RC2 between the detection limit C2 and the detection limit WD(far), as shown by reference numeral 8B in Figure 8. In this case, two bright spot images 30A and one bright spot image 30C appear in a defocused state in the captured image 34, as shown by reference numeral 8E in Figure 8. This makes it possible to determine that the Z-direction position of the optical head 5 is within the overlapping range between the predetermined range and the far range.

[0069] When the Z-direction position of the optical head 5 is within the range excluding the overlapping range with a predetermined range within the far range (hereinafter referred to as the "non-overlapping far range"), as shown by reference numeral 8A in Figure 8, the eye under examination E is positioned within the range RC3 between the detection limit WD(far) and the detection limit C1. In this case, as shown by reference numeral 8D in Figure 8, two bright spot images 30A disappear from the captured image 34, and only one bright spot image 30D remains in the captured image 34. This makes it possible to determine that the optical head 5 is located within the non-overlapping far range.

[0070] The presence or absence of each bright spot image 30A to 30C in the captured image 34 changes depending on the Z-direction position of the optical head 5. Therefore, by detecting the presence or absence of each bright spot image 30A to 30C in the captured image 34, it is possible to determine whether the optical head 5 is within a predetermined range, a non-overlapping near range, or a non-overlapping far range. In other words, it is possible to determine whether the eye under examination E is within the ranges RA1, RA2, RB3, or RC3 relative to the optical head 5.

[0071] Furthermore, when detecting the presence or absence of each bright spot image 30A to 30C in the captured image 34, the parallel light projection units 13B and 13C are located on the outer periphery of the keratin plate 12h (each parallel light projection unit 13A). As a result, the positions of the bright spot images 30B and 30C in the captured image 34 are separated from the positions of the two bright spot images 30A (making them less likely to overlap). Therefore, it becomes easier to distinguish between the two bright spot images 30A, the bright spot image 30B, and the bright spot image 30C, allowing the optical head 5 to accurately determine whether it is within the predetermined range, the non-overlapping near range, or the non-overlapping far range.

[0072] <Functions of the control device 9> Figure 9 is a functional block diagram of the control device 9. As shown in Figure 9, the control device 9 comprehensively controls the operation of each part of the ophthalmic device 1 to perform XYZ alignment of the optical head 5 with respect to the eye E under examination and measurement of the eye characteristics of the eye E under examination. The control device 9 is connected to the face support unit 3, the drive mechanism 4, the various systems 12 to 17 of the optical head 5, the keratinizing light source 12i, and the display unit 6.

[0073] The control device 9 includes an arithmetic circuit composed of various processors and memory. These processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices [e.g., SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays)]. The various functions of the control device 9 may be implemented by a single processor, or by multiple processors of the same or different types.

[0074] The control device 9 functions as an alignment control unit 40, an eye characteristic measurement control unit 42, and an eye characteristic calculation unit 44 by executing a control program stored in a memory unit (not shown).

[0075] Before the start of eye measurement of the eye E under examination, the alignment control unit 40 controls the observation system 12, keratling light source 12i, parallel light projection system 13, XY alignment system 14, and target projection system 15, etc., to perform XY alignment and Z alignment of the optical head 5 for the eye E under examination.

[0076] A known method is used for XY alignment. The alignment control unit 40 first controls the observation system 12, XY alignment system 14, and target projection system 15, etc., to perform XY alignment detection to detect the relative position of the optical head 5 in the XY direction with respect to the eye E under examination. Then, based on the detection result of the XY alignment detection, the alignment control unit 40 drives the drive mechanism 4 to move the optical head 5 in the XY direction, thereby performing XY alignment of the optical head 5 with respect to the eye E under examination.

[0077] On the other hand, when performing Z-alignment, the alignment control unit 40 starts the emission of parallel light from each of the parallel light projection units 13A to 13C of the parallel light projection system 13, the emission of a ring-shaped light beam from the keratin light source 12i, and the imaging of the anterior segment (cornea Ec) of the eye E under examination by the observation system 12.

[0078] Next, as shown in Figures 7 and 8 described above, the alignment control unit 40 determines whether or not the optical head 5 is within a predetermined range, a non-overlapping near range, or a non-overlapping far range by determining the presence or absence of bright spot images 30A to 30C in the captured image 34 output from the image sensor 12g of the observation system 12.

[0079] For example, the alignment control unit 40 determines that the optical head 5 is within a predetermined range in the Z direction if at least two bright spot images 30A appear in the captured image 34 among the bright spot images 30A to 30C. Furthermore, the alignment control unit 40 determines that the optical head 5 is within a non-overlapping near range and the position of the eye E is approaching the optical head 5 beyond the detection limit WD(near) if bright spot images 30A and 30C disappear and bright spot image 30B appears in the captured image 34. Additionally, the alignment control unit 40 determines that the optical head 5 is within a non-overlapping far range in the Z direction and the position of the eye E is moving away from the optical head 5 beyond the detection limit WD(far). This expands the detection range of the eye E in the Z direction by the optical head 5.

[0080] If the alignment control unit 40 determines that the optical head 5 is within a non-overlapping near range or non-overlapping far range in the Z direction, it drives the drive mechanism 4 based on the determination result to adjust the position of the optical head 5 in the Z direction to within a predetermined range. This makes it possible to calculate the distance in the Z direction between the optical head 5 and the eye E under examination based on the captured image 34 (two bright spot images 30A and a keratling image 32).

[0081] Figure 10 is an explanatory diagram illustrating an example of a method for calculating the Z-direction distance between the optical head 5 and the eye under examination E based on the captured image 34. As shown in Figure 10, the distance LA between the two bright spot images 30A in the captured image 34 is approximately constant regardless of the Z-direction distance between the optical head 5 and the eye under examination E, since each parallel light projection unit 13A is an infinite-distance illumination source (see symbol IIIA in Figure 3 described above). On the other hand, the distance LB between the inner ring images of the keratin ring image 32 in the captured image 34 increases or decreases depending on the Z-direction distance between the optical head 5 and the eye under examination E, since the keratin ring light source 12i is a finite-distance illumination source (see symbol IIIB in Figure 3 described above).

[0082] The alignment control unit 40 calculates the Z-direction distance between the optical head 5 and the eye under examination E in a known manner based on the ratio of the distance LA between the two bright spot images 30A and the distance LB between the keratinizing images 32. In this case, the alignment control unit 40 functions as the distance calculation unit of the present invention. Then, based on the calculation result of this Z-direction distance, the alignment control unit 40 drives the drive mechanism 4 to move the optical head 5 in the Z direction, thereby performing Z-alignment of the optical head 5 with respect to the eye under examination E.

[0083] Returning to Figure 9, after the alignment described above is completed, the eye characteristic measurement control unit 42 controls the observation system 12, keratinizing light source 12i, measurement pattern projection system 16, and target projection system 15, etc., to perform keratometry, which measures the corneal shape of the eye E, and refractometry, which measures the refractive power of the eye E, as eye characteristic measurements of the eye E under examination. In addition, the eye characteristic calculation unit 44 calculates the corneal shape of the eye E under examination if keratometry is performed, and calculates the refractive power of the eye E under examination if refractometry is performed.

[0084] For example, in keratometry of the eye E under examination, the eye characteristic measurement control unit 42 turns on the keratography ring light source 12i to project a ring-shaped beam of light onto the cornea Ec, and causes the image sensor 12g to image the ring-shaped beam of light reflected by the cornea Ec. Next, the eye characteristic calculation unit 44 calculates the corneal shape of the eye E under examination (corneal refractive power, corneal astigmatism, and corneal astigmatism axis angle, etc.) using a known method based on the keratography ring image 32 in the captured image 34 output from the image sensor 12g.

[0085] In the refraction measurement of the eye E under examination, a preliminary measurement and a final measurement are performed. In the preliminary measurement, the eye characteristic measurement control unit 42 controls the target projection system 15 (target display unit 15a) to present a fixation target to the eye E under examination. Next, the eye characteristic measurement control unit 42 controls the measurement pattern projection system 16 (LED light source 16h and rotary prism 16f, etc.) to project a ring-shaped measurement pattern light beam onto the fundus Ef, and causes the light receiving system 17 (image sensor 12g) to capture the fundus reflected light (ring image) reflected by the fundus Ef.

[0086] Then, the eye characteristic calculation unit 44 calculates the provisional spherical power and astigmatism power of the eye E under examination using a known method, based on the captured ring image output from the image sensor 12g. Based on the calculation results of the spherical power and astigmatism power in this provisional measurement, the eye characteristic measurement control unit 42 drives the interlocking movement mechanism 27 to move the focusing lens 15e, the refractor measurement unit 16a, and the focusing lens 17d to the position of the transmitted spherical power. This provisional measurement process may be repeated multiple times.

[0087] In this measurement, the eye characteristic measurement control unit 42 drives the interlocking movement mechanism 27 to move the focusing lens 15e from the position determined in the preliminary measurement to the clouding position, thereby promoting clouding of the eye E under examination. The eye characteristic measurement control unit 42 then controls the measurement pattern projection system 16 and the light receiving system 17 in the same manner as in the preliminary measurement to project a ring-shaped measurement pattern light beam onto the fundus Ef and to capture a ring image with the image sensor 12g. Next, the eye characteristic calculation unit 44 calculates the refractive power (spherical power, astigmatism power, astigmatism axis angle) of the eye E under examination using a known method based on the ring image and the amount of movement of the focusing lens 15e.

[0088] <Operation of the ophthalmic device 1 in the first embodiment> Figure 11 is a flowchart showing the flow of the measurement process of the ocular characteristics of the eye E being examined by the ophthalmic device 1 of the first embodiment, particularly the Z-alignment process.

[0089] As shown in Figure 11, after the subject's face is supported by the face support unit 3, when the examiner inputs a measurement start operation on the operation menu screen of the display unit 6, the alignment control unit 40 starts the XYZ alignment of the optical head 5 with respect to the subject's eye E (step S1). The alignment control unit 40 then controls each part of the optical head 5 to perform XY alignment detection of the optical head 5 with respect to the subject's eye E using a known method.

[0090] Furthermore, the alignment control unit 40 initiates the emission of parallel light from each of the parallel light projection units 13A to 13C of the parallel light projection system 13, the emission of a ring-shaped light beam from the keratin light source 12i, and the imaging of the anterior segment (cornea Ec) of the eye E under examination by the observation system 12 (step S2).

[0091] Next, the alignment control unit 40 determines whether the optical head 5 is within a predetermined range, a non-overlapping near range, or a non-overlapping far range in the Z direction, based on the presence or absence of each bright spot image 30A to 30C in the captured image 34 output from the image sensor 12g of the observation system 12 (step S3).

[0092] Then, if the alignment control unit 40 determines that the optical head 5 is within the non-overlapping near range or non-overlapping far range in the Z direction, it drives the drive mechanism 4 based on the determination result to adjust the position of the optical head 5 in the Z direction to within a predetermined range (NO in step S3, step S4). The processes of steps S3 and S4 are then repeatedly executed until YES is determined in step S3.

[0093] If the alignment control unit 40 determines YES in step S3, it calculates the Z-direction distance between the optical head 5 and the eye under examination E based on the distance LA between the two bright spot images 30A in the captured image 34 and the distance LB between the keratinized image 32 (step S5). Then, based on the calculation result of this Z-direction distance, the alignment control unit 40 drives the drive mechanism 4 to perform Z-alignment of the optical head 5 with respect to the eye under examination E (step S6). In addition, based on the XY-direction alignment detection results described above, the alignment control unit 40 drives the drive mechanism 4 to perform XY alignment of the optical head 5 with respect to the eye under examination E.

[0094] Once XYZ alignment is complete, the eye characteristic measurement control unit 42 controls the observation system 12, keratinizing light source 12i, measurement pattern projection system 16, target projection system 15, etc., to perform keratin and refractory measurements of the eye E under examination. In addition, the eye characteristic calculation unit 44 calculates the corneal shape of the eye E under examination during keratin measurement and calculates the refractive power of the eye E under examination during refractory measurement. As a result, eye characteristic measurement data (corneal shape, refractive power) of the eye E under examination is obtained (step S7).

[0095] As described above, in the ophthalmic device 1 of the first embodiment, by providing parallel light projection units 13B and 13C on the optical head 5, it is possible to determine whether the optical head 5 is outside a predetermined range in the Z direction, within a non-overlapping near range or non-overlapping far range (i.e., whether the eye E under examination is within range RB3 or range RC3). This makes it possible to extend the detection range of the eye E under examination in the Z direction of the optical head 5 with a simple configuration. As a result, Z-alignment of the optical head 5 can be performed even when the optical head 5 is not within a predetermined range in the Z direction. Furthermore, since it is no longer necessary to provide a Z-alignment system using an optical lever type on the optical head 5 as in the conventional method, the ophthalmic device 1 can be made lower cost and smaller.

[0096] [Second Embodiment] Figure 12 is an explanatory diagram illustrating the parallel light projection units 13B and 13C of the ophthalmic apparatus 1 of the second embodiment. The upper part of Figure 12 (labeled XIIA to XIIC) is an explanatory diagram illustrating the change in position and orientation of the parallel light projection units 13B and 13C according to the Z-direction distance between the eye E under examination and the optical head 5. The lower part of Figure 12 (labeled XIID to XIIF) shows the captured images 34 corresponding to the upper part of Figure 12.

[0097] In the ophthalmic apparatus 1 of the first embodiment described above, the parallel light projection units 13B and 13C are fixedly positioned on the front surface of the optical head 5. However, as shown in Figure 12, in the ophthalmic apparatus 1 of the second embodiment, at least one of the position and orientation (incident angle of parallel light) of the parallel light projection units 13B and 13C can be displaced. The ophthalmic apparatus 1 of the second embodiment has basically the same configuration as the ophthalmic apparatus 1 of the first embodiment described above, except that the optical head 5 is provided with a displacement mechanism 50. For this reason, components that are functionally or structurally identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0098] The displacement mechanism 50 is an actuator that, under the control of the alignment control unit 40, can displace at least one of the position and orientation (incident angle of parallel light) of the parallel light projection units 13B and 13C. Note that a separate displacement mechanism 50 may be provided for each of the parallel light projection units 13B and 13C. By displacing the position and orientation of the parallel light projection unit 13B using the displacement mechanism 50, the Z-direction position range of the optical head 5 from which the bright spot image 30B appears in the captured image 34 can be arbitrarily changed. Similarly, by displacing the position and orientation of the parallel light projection unit 13C using the displacement mechanism 50, the Z-direction position range of the optical head 5 from which the bright spot image 30C appears in the captured image 34 can be arbitrarily changed.

[0099] For example, as shown by the symbols XIIA and XIID in Figure 12, in the first embodiment, the far range of the optical head 5 in which the bright spot image 30C appears in the captured image 34 (the range in which the eye under examination E is positioned between detection limits C1 and C2) is fixed. Therefore, when the optical head 5 moves beyond the far range and away from the eye under examination E, as shown by the symbols XIIB and XIIE in Figure 12, the eye under examination E moves relatively far from the optical head 5 to a position beyond the detection limit C1, and the bright spot image 30C no longer appears in the captured image 34. In this case, the Z-direction position of the optical head 5 becomes unknown, and therefore it is not possible to adjust the Z-direction position of the optical head 5.

[0100] In contrast, in the second embodiment, as shown by the symbols XIIC and XIIF in Figure 12, the displacement mechanism 50 displaces at least one of the position and orientation of the parallel light projection unit 13C to change the position of the far range (detection limits C1, C2), thereby making the bright spot image 30C appear in the captured image 34 even in the state shown by symbol XIIB. Although not shown in the figure, the displacement mechanism 50 displaces at least one of the position and orientation of the parallel light projection unit 13B, so that even when the optical head 5 approaches the eye E beyond the near range (when the eye E approaches the optical head 5 beyond the detection limit B1), the bright spot image 30B can appear in the captured image 34 by changing the position of the near range (detection limits B1, B2).

[0101] In the second embodiment, if none of the bright spot images 30A to 30C appear in the captured image 34, the alignment control unit 40 drives the displacement mechanism 50 to displace the position and orientation of the parallel light projection units 13B and 13C until either the bright spot image 30B or 30C appears in the captured image 34. Once either the bright spot image 30B or 30C appears in the captured image 34, the Z-direction position of the optical head 5 becomes clear, and the alignment control unit 40 can drive the drive mechanism 4 to adjust the position of the optical head 5 within a predetermined range.

[0102] As described above, in the ophthalmic apparatus 1 of the second embodiment, the position and orientation of the parallel light projection units 13B and 13C can be displaced by the displacement mechanism 50, thereby expanding the detection range of the eye under examination E in the Z direction of the optical head 5 compared to the first embodiment. Furthermore, the same effects as in the first embodiment can be obtained.

[0103] [Third Embodiment] Figure 13 is an explanatory diagram illustrating the parallel light projection unit 13D of the ophthalmic apparatus 1 according to the third embodiment. The upper part of Figure 13 (labeled XIIIA to XIIIC) is an explanatory diagram illustrating the change in position and orientation of the parallel light projection unit 13D according to the Z-direction distance between the eye E under examination and the optical head 5. The lower part of Figure 13 (labeled XIIID to XIIIF) shows the captured images 34 corresponding to the upper part of Figure 13.

[0104] In each of the above embodiments, the optical head 5 is provided with two parallel light projection units 13B and 13C. However, as shown in Figure 13, the optical head 5 of the ophthalmic apparatus 1 of the third embodiment is provided with one parallel light projection unit 13D and a displacement mechanism 50 instead of the parallel light projection units 13B and 13C. The ophthalmic apparatus 1 of the third embodiment has basically the same configuration as the ophthalmic apparatus 1 of each of the above embodiments, except that it is equipped with the parallel light projection unit 13D and the displacement mechanism 50. For this reason, components that are functionally or structurally identical to those in each of the above embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0105] The parallel light projection unit 13D (corresponding to the second parallel light projection unit of the present invention) is basically the same as the parallel light projection units 13B and 13C of the second embodiment described above, and its orientation (incidence angle of parallel light) is displaceable. The displacement mechanism 50 of the third embodiment (corresponding to the incidence angle switching unit of the present invention) is an actuator that can displace the orientation of the parallel light projection unit 13D, that is, change the incidence angle of parallel light, under the control of the alignment control unit 40.

[0106] Specifically, the displacement mechanism 50 can switch the incidence angle of parallel light projected by the parallel light projection unit 13D between a normal incidence angle (see symbol XIIIB), a near-range incidence angle (see symbol XIIIC), and a far-range incidence angle (see symbol XIIIA). The normal incidence angle corresponds to the first incidence angle of the present invention, and the near-range and far-range incidence angles correspond to the second incidence angle of the present invention.

[0107] The normal incidence angle (see symbol XIIIB) is the incidence angle of parallel light corresponding to when the optical head 5 is within a predetermined range in the Z direction (within the range where the eye E under examination is positioned between detection limit WD(near) and detection limit WD(far)). The near-range incidence angle (see symbol XIIIC) is the incidence angle of parallel light corresponding to when the optical head 5 is in the near range in the Z direction (within the range where the eye E under examination is positioned between detection limit B1 and detection limit B2). The far-range incidence angle (see symbol XIIIA) is the incidence angle of parallel light corresponding to when the optical head 5 is in the far range in the Z direction (within the range where the eye E under examination is positioned between detection limit C1 and detection limit C2).

[0108] When the parallel light projection unit 13D is switched to the normal incident angle by the displacement mechanism 50, and the optical head 5 is within a predetermined range, in addition to the two bright spot images 30A described above, a bright spot image 30D corresponding to the reflected light of the parallel light projected by the parallel light projection unit 13D appears in the captured image 34 (see symbol XIIIE).

[0109] When the parallel light projection unit 13D is switched to the near-range incidence angle by the displacement mechanism 50, and the optical head 5 is in the near-range, a bright spot image 30D appears in the captured image 34 (see symbol XIIIF). Although not shown in the illustration, when the optical head 5 is in the overlapping range between the predetermined range and the near-range (when the eye under examination E is positioned between the detection limit WD (near) and the detection limit B2), two bright spot images 30A and one bright spot image 30D appear in the captured image 34 in a defocused state.

[0110] When the parallel light projection unit 13D is switched to the far-range incidence angle by the displacement mechanism 50, and the optical head 5 is within the far-range, a bright spot image 30D appears in the captured image 34 (see symbol XIIID). Although not shown in the illustration, when the optical head 5 is within the overlapping range of the predetermined range and the far-range (when the eye under examination E is positioned between the detection limit C2 and the detection limit WD(far)), two bright spot images 30A and one bright spot image 30D appear in the captured image 34 in a defocused state.

[0111] The position of the bright spot image 30D that appears in the captured image 34 varies depending on the angle of incidence of the parallel light projected by the parallel light projection unit 13D. Specifically, the more obtuse the angle of incidence of the parallel light to the eye E under examination, the further the bright spot image 30 is from the center of the keratling image 32. Therefore, based on the presence or absence of each bright spot image 30A, 30D in the captured image 34 and the position of the bright spot image 30D, it is possible to determine whether the optical head 5 is within a predetermined range, within a non-overlapping near range, or within a non-overlapping far range in the Z direction.

[0112] In the third embodiment, the alignment control unit 40 controls, for example, the displacement mechanism 50 to switch between three types of incident angles of parallel light from the parallel light projection unit 13D (normal incident angle, near-range incident angle, and far-range incident angle) in any order, and acquires an image 34 from the image sensor 12g of the observation system 12 each time the incident angle is switched.

[0113] For example, when the optical head 5 is within a predetermined range, at least two bright spot images 30A and one bright spot image 30D appear in the captured image 34 taken at the normal incident angle. Also, when the optical head 5 is within the non-overlapping near range, the bright spot image 30D appears in the captured image 34 taken at the near range incident angle, and the bright spot images 30A and 30D do not appear in the remaining two captured images 34. Furthermore, when the optical head 5 is within the non-overlapping far range, the bright spot image 30D appears in the captured image 34 taken at the far range incident angle, and the bright spot images 30A and 30D do not appear in the remaining two captured images 34.

[0114] Therefore, the alignment control unit 40 can determine whether the optical head 5 is within a predetermined range, a non-overlapping near range, or a non-overlapping far range based on the captured image 34 for each incident angle, and can drive the drive mechanism 4 to adjust the position of the optical head 5 within the predetermined range.

[0115] Alternatively, the alignment control unit 40 may first control the displacement mechanism 50 to switch the parallel light projection unit 13D to the normal incidence angle, then acquire an image 34 from the image sensor 12g, and determine whether the optical head 5 is within a predetermined range based on this image 34. If the optical head 5 is not within the predetermined range, the alignment control unit 40 controls the displacement mechanism 50 to switch the parallel light projection unit 13D to the near-range incidence angle, then acquires an image 34 from the image sensor 12g, and determines whether the optical head 5 is within the non-overlapping near-range based on this image 34. Furthermore, if the optical head 5 is not within the non-overlapping near-range either, the alignment control unit 40 controls the displacement mechanism 50 to switch the parallel light projection unit 13D to the far-range incidence angle, then acquires an image 34 from the image sensor 12g, and determines whether the optical head 5 is within the non-overlapping far-range based on this image 34.

[0116] As described above, in the ophthalmic apparatus 1 of the third embodiment, the orientation (incidence angle of parallel light) of one parallel light projection unit 13D can be displaced by the displacement mechanism 50, thereby expanding the detection range of the eye under examination E in the Z direction of the optical head 5, similar to the embodiments described above. As a result, only one parallel light projection unit 13D needs to be added, which reduces costs compared to the embodiments described above.

[0117] In addition, in the ophthalmic apparatus 1 of the third embodiment, the position and orientation of the parallel light projection unit 13D may be arbitrarily displaced by the displacement mechanism 50, similar to the second embodiment described above.

[0118] [Modified version of the third embodiment] Figures 14 and 15 are explanatory diagrams illustrating a modified parallel light projection unit 13D of the ophthalmic apparatus 1 of the third embodiment. In the ophthalmic apparatus 1 of the third embodiment described above, the incident angle of parallel light on the eye E under examination by the parallel light projection unit 13D is switched by displacing the orientation of the parallel light projection unit 13D using the displacement mechanism 50, but the incident angle of parallel light may be switched by other methods. Note that the modified versions shown in Figures 14 and 15 have basically the same configuration as the ophthalmic apparatus 1 of the third embodiment described above, except that the method of switching the incident angle of parallel light is different. For this reason, parts that are functionally or structurally identical to those in each of the above embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0119] In the modified example shown in Figure 14, the position of the parallel light projection unit 13D is fixed, and a prism 60 is added, while the position and orientation of this prism 60 are made displaceable by the displacement mechanism 50. In this case, the displacement mechanism 50 and the prism 60 constitute the incident angle switching unit of the present invention.

[0120] As shown by labels XIVB and XIVE in Figure 14, the displacement mechanism 50 retracts the prism 60 from the optical path of the parallel light emitted from the parallel light projection unit 13D (hereinafter simply referred to as "the emitted optical path") when setting the angle of incidence of the parallel light from the parallel light projection unit 13D to the eye under examination E to the previously described normal incidence angle.

[0121] As shown in Figure 14, the displacement mechanism 50, when setting the incident angle of parallel light from the parallel light projection unit 13D to the eye under examination E to the aforementioned near-range incident angle, positions the prism 60 in the near-range position and orientation (angle, etc.) on the exit light path. The near-range position and orientation is the position and orientation (angle) of the prism 60 such that the incident angle of parallel light becomes the near-range incident angle, and is determined in advance.

[0122] As shown in Figure 14, the displacement mechanism 50, when setting the incidence angle of parallel light from the parallel light projection unit 13D to the eye under examination E to the far-range incidence angle described above, positions the prism 60 in the far-range position and orientation (angle, etc.) on the exit light path. The near-range position and orientation is the position and orientation (angle) of the prism 60 such that the incidence angle of parallel light becomes the far-range incidence angle, and is determined in advance.

[0123] In this way, the displacement mechanism 50 allows the prism 60 to be inserted into or removed from the light path, or the position and orientation of the prism 60 to be displaced, thereby achieving the same effects as in the third embodiment described above.

[0124] Alternatively, instead of changing the position and orientation of the prism 60 by the displacement mechanism 50 as shown in Figure 14, the projection lens 131 (see Figure 2) of the parallel light projection unit 13D may be replaced with a tilted projection lens 131A or projection lens 131B (corresponding to the incident angle switching part of the present invention) that has a prism function, as shown in Figure 15. Note that the illustration of each parallel light projection unit 13A is omitted in Figure 15.

[0125] The transmission deviation of projection lens 131A (see symbol XVA in Figure 15) is an angle that adjusts the incident angle of parallel light to the eye under examination E to the aforementioned near-range incident angle, and is predetermined according to the arrangement of light source 130 and projection lens 131A and the working distance of objective lens 12a. Similarly, the transmission deviation of projection lens 131B (see symbol XVB in Figure 15) is an angle that adjusts the incident angle of parallel light to the eye under examination E to the aforementioned far-range incident angle, and is predetermined according to the arrangement of light source 130 and projection lens 131B and the working distance of objective lens 12a.

[0126] By providing the parallel light projection unit 13D with either the projection lens 131A or the projection lens 131B, the same effects as those of the third embodiment described above can be obtained.

[0127] [Fourth Embodiment] Figure 16 is a perspective view of the front of the optical head 5 of the ophthalmic apparatus 1 of the fourth embodiment. Figure 17 is a front view of the front of the optical head 5 of the ophthalmic apparatus 1 of the fourth embodiment. In the ophthalmic apparatus 1 of the first and second embodiments described above, the parallel light projection units 13B and 13C are provided on the outer periphery of the keratin plate 12h and on a straight line L, as shown in Figure 5 described above.

[0128] In contrast, as shown in Figures 16 and 17, in the ophthalmic apparatus 1 of the fourth embodiment, the parallel light projection units 13B and 13C are located on the outer periphery of the keratin plate 12h and below each parallel light projection unit 13A in the Y direction when the keratin plate 12h is viewed from the front side in the Z direction. The ophthalmic apparatus 1 of the fourth embodiment is basically the same configuration as the ophthalmic apparatus 1 of the first and second embodiments, except for the difference in the positions of the parallel light projection units 13B and 13C. Therefore, components that are functionally or structurally identical to those in the above embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0129] During the measurement of the ocular characteristics of the eye E under examination, the upper eyelid of the subject (especially the elderly) may droop. In this case, with the ophthalmic device 1 of the first and second embodiments described above, there is a risk that the parallel light emitted from the parallel light projection units 13B and 13C may be vignetted by the upper eyelid. In contrast, with the ophthalmic device 1 of the fourth embodiment, the parallel light projection units 13B and 13C project parallel light onto the eye E under examination from a diagonally downward side, thereby preventing the parallel light from being vignetted by the upper eyelid.

[0130] In addition, in the ophthalmic apparatus 1 of the third embodiment described above, one parallel light projection unit 13D may be provided at a position lower in the Y direction than each parallel light projection unit 13A, similar to the fourth embodiment.

[0131] [others] Figure 18 shows a modified example of the observation system 12. In the embodiments described above, the case in which the observation system 12 is an object-side telecentric optical system was used as an example, but as shown in Figure 18, the observation system 12 does not have to be an object-side telecentric optical system. Even in this case, it is possible to determine whether the optical head 5 is within a predetermined range, a non-overlapping near range, or a non-overlapping far range in the Z direction.

[0132] Figure 19 is an explanatory diagram illustrating the calculation of the Z-direction distance between the eye E and the optical head 5 based on the captured image 34 obtained when there is one parallel light projection unit 13A. In each of the above embodiments, the optical head 5 is provided with two (or more) parallel light projection units 13A, but the number of parallel light projection units 13A may be as few as one.

[0133] When the optical head 5, which is equipped with one parallel light projection unit 13A, is within a predetermined range, an image 34 as shown in Figure 19 is obtained. In this case, the alignment control unit 40 calculates the Z-direction distance between the optical head 5 and the eye under examination E based on the ratio of the interval LA1, which is the distance from the center position C of the keratling image 32 to the bright spot image 30A, to the interval LB described above. Note that the distance from the bright spot to the bright spot image 30A for XY alignment may be used as the interval LA1, although it is not shown in the figure. This allows Z-alignment to be performed in the same manner as in each of the above embodiments.

[0134] In each of the above embodiments, an autorefractor / keratometer was used as an example of the ophthalmic device 1 of the present invention, but the present invention is applicable to various known ophthalmic devices that perform Z-alignment of various optical heads (in particular, various ophthalmic devices equipped with an object-side telecentric optical system).

[0135] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0136] [Additional note 1] Optical head and The optical head is provided with one or more parallel light projection units that project parallel light onto the eye under examination, An observation system comprising an objective lens and an image sensor, wherein when reflected parallel light projected onto the eye under examination enters the image sensor through the objective lens, the image sensor captures a bright spot image of the reflected light. Equipped with, An ophthalmic device in which the position range in the direction along the principal optical axis of the optical head, where the bright spot image is captured by the image sensor, includes at least a range outside a predetermined range based on a position that is a distance from the eye under examination by the working distance of the objective lens.

[0137] [Additional note 2] The parallel light projection unit includes one or more first parallel light projection units and one or more second parallel light projection units. The first position range in the direction along the principal optical axis of the optical head, where the bright spot image corresponding to the first parallel light projection unit is captured by the image sensor, is the predetermined range. The ophthalmic apparatus according to Appendix 1, wherein the second position range in the direction along the principal optical axis of the optical head, in which the bright spot image corresponding to the second parallel light projection unit is captured by the image sensor, includes at least the area outside the range.

[0138] [Additional note 3] The ophthalmic device according to Appendix 2, wherein the first position range and the second position range partially overlap with each other.

[0139] [Additional note 4] The second position range includes a near range which includes at least a range closer to the eye under examination than the predetermined range, and a far range which does not overlap with the near range and includes at least a range further from the eye under examination than the predetermined range. The second parallel light projection unit, A near-field parallel light projection unit is provided at a position where the bright spot image is captured by the image sensor when the optical head is at least within the near-field range, and where the bright spot image is not captured by the image sensor when the optical head is within the far-field range. A distance parallel light projection unit is provided at a position where the bright spot image is captured by the image sensor when the optical head is at least within the far range, and where the bright spot image is not captured by the image sensor when the optical head is within the near range. An ophthalmic device as described in Appendix 2 or 3, including the following:

[0140] [Additional note 5] At least one of the position of the near-vision parallel light projection unit and the angle of incidence of the parallel light from the near-vision parallel light projection unit to the eye under examination is changeable. The ophthalmic apparatus according to Appendix 4, wherein at least one of the position of the distance parallel light projection unit and the angle of incidence of the parallel light from the distance parallel light projection unit to the eye under examination is changeable.

[0141] [Additional note 6] The number of the second parallel light projection units is one, The second position range includes a near range which includes at least a range closer to the eye under examination than the predetermined range, and a far range which does not overlap with the near range and includes at least a range further from the eye under examination than the predetermined range. The second parallel light projection unit includes an incident angle switching unit that can switch the incident angle of the parallel light onto the eye under examination between a first incident angle and a second incident angle. The first incidence angle is an angle at which the bright spot image is captured by the image sensor when the optical head is within the near range, but the bright spot image is not captured by the image sensor when the optical head is within the far range. The ophthalmic apparatus according to Appendix 2 or 3, wherein the second incidence angle is an angle at which the bright spot image is captured by the image sensor when the optical head is within the far range, but the bright spot image is not captured by the image sensor when the optical head is within the near range.

[0142] [Additional note 7] The ophthalmic apparatus according to any one of the appendices 2 to 6, wherein the second parallel light projection unit is provided at the outer peripheral position of the first parallel light projection unit when the optical head is viewed from one direction of the principal optical axis.

[0143] [Additional note 8] The first parallel light projection unit is provided at a position offset in the left-right direction from the principal light axis when the optical head is viewed from one direction of the principal light axis, The ophthalmic apparatus according to any one of the appendices 2 to 6, wherein the second parallel light projection unit is located below the first parallel light projection unit when the optical head is viewed from the one direction.

[0144] [Additional note 9] Equipped with a finite-distance illumination light source that provides illumination at a finite distance, The observation system is an object-side telecentric optical system, and captures an image of the eye under examination onto which the parallel light and illumination light from the finite-distance illumination source are projected. An ophthalmic apparatus according to any one of the appendices 1 to 8, comprising a distance calculation unit that calculates the distance between the optical head and the eye under examination based on the captured image including the bright spot image and the image of the illumination light.

[0145] [Additional Note 10] The ophthalmic apparatus according to Appendix 9, wherein the finite-distance illumination source is a keratinizing light source. [Explanation of symbols]

[0146] 1…Ophthalmology equipment 2…Bass 3…Face support section 4…Drive mechanism 5…Optical head 6…Display section 9...Control device 12… Observation-based 12a…Objective lens 12b... Dichroic filter 12c... Half mirror 12d… Relay lens 12e... Dichroic filter 12f...imaging lens 12g…image sensor 12h... Geratolite 12i...Keratling light source 13…Parallel light projection system 13A, 13B, 13C, 13D… Parallel light projection units 14…XY Alignment System 14a... Alignment light source 14b…Projection lens 15...Optotype projection system 15a...Optotype display section 15b... Half mirror 15c… Relay lens 15d... Reflective mirror 15e… ​​Focusing lens 15f… Relay lens 15g…Field lens 15h...VCC lens 15i…Reflective mirror 15j... Dichroic filter 15k... Glare light source 16…Measurement pattern projection system 16a...Ref measurement unit 16b…Relay lens 16c... Eye Ring 16d…Field lens 16e...Perforated prism 16f... Rotary prism 16h…LED light source 16i...Collimator lens 16j... Conical prism 16k…forming plate 17...Light receiving system 17a…Field lens 17b... Reflective mirror 17c… Relay lens 17d... Focusing lens 17e... Reflective mirror 27... Interlocking movement mechanism 30A, 30B, 30C, 30D... Bright spot image 32... Keratling statue 34… Captured image 40… Alignment Control Unit 42…Eye characteristic measurement and control unit 44...Eye characteristic calculation section 50…Displacement mechanism 60...Prism 130...Light source 131, 131A, 131B… Projection lenses C…Center position E...Eye being examined Ec…cornea Ef…fundus O1…main optical axis O2, O3, O4... Optical axis

Claims

1. Optical head and The optical head is provided with one or more parallel light projection units that project parallel light onto the eye under examination, An observation system comprising an objective lens and an image sensor, wherein when reflected parallel light projected onto the eye under examination enters the image sensor through the objective lens, the image sensor captures a bright spot image of the reflected light. Equipped with, An ophthalmic device in which the position range in the direction along the principal optical axis of the optical head, where the bright spot image is captured by the image sensor, includes at least a range outside a predetermined range based on a position that is a distance from the eye under examination by the working distance of the objective lens.

2. The parallel light projection unit includes one or more first parallel light projection units and one or more second parallel light projection units, The first position range in the direction along the principal optical axis of the optical head, in which the bright spot image corresponding to the first parallel light projection unit is captured by the image sensor, is the predetermined range. The ophthalmic apparatus according to claim 1, wherein the second position range in the direction along the principal optical axis of the optical head, in which the bright spot image corresponding to the second parallel light projection unit is captured by the image sensor, includes at least the area outside the range.

3. The ophthalmic apparatus according to claim 2, wherein the first position range and the second position range partially overlap with each other.

4. The second position range includes a near range which includes at least a range closer to the eye under examination than the predetermined range, and a far range which does not overlap with the near range and includes at least a range further from the eye under examination than the predetermined range. The second parallel light projection unit, A near-field parallel light projection unit is provided at a position where the bright spot image is captured by the image sensor when the optical head is within the near-field range, and where the bright spot image is not captured by the image sensor when the optical head is within the far-field range. A distance parallel light projection unit is provided at a position where the bright spot image is captured by the image sensor when the optical head is within the far range, and where the bright spot image is not captured by the image sensor when the optical head is within the near range. The ophthalmic apparatus according to claim 2, including the following:

5. At least one of the position of the near-vision parallel light projection unit and the angle of incidence of the parallel light from the near-vision parallel light projection unit to the eye under examination is changeable. The ophthalmic apparatus according to claim 4, wherein at least one of the position of the distance parallel light projection unit and the angle of incidence of the parallel light from the distance parallel light projection unit to the eye under examination is changeable.

6. The number of the second parallel light projection units is one, The second position range includes a near range which includes at least a range closer to the eye under examination than the predetermined range, and a far range which does not overlap with the near range and includes at least a range further from the eye under examination than the predetermined range. The second parallel light projection unit includes an incident angle switching unit that can switch the incident angle of the parallel light onto the eye under examination between a first incident angle and a second incident angle. The first incidence angle is an angle at which the bright spot image is captured by the image sensor when the optical head is within the near range, but the bright spot image is not captured by the image sensor when the optical head is within the far range. The ophthalmic apparatus according to claim 2, wherein the second incidence angle is an angle at which the bright spot image is captured by the image sensor when the optical head is within the far range, but the bright spot image is not captured by the image sensor when the optical head is within the near range.

7. The ophthalmic apparatus according to any one of claims 2 to 6, wherein the second parallel light projection unit is provided at the outer peripheral position of the first parallel light projection unit when the optical head is viewed from one direction of the principal optical axis.

8. The first parallel light projection unit is provided at a position offset in the left-right direction from the principal optical axis when the optical head is viewed from one direction of the principal optical axis, The ophthalmic apparatus according to any one of claims 2 to 6, wherein the second parallel light projection unit is located below the first parallel light projection unit when the optical head is viewed from the one direction.

9. Equipped with a finite-distance illumination light source that provides illumination at a finite distance, The observation system is an object-side telecentric optical system, and captures an image of the eye under examination onto which the parallel light and illumination light from the finite-distance illumination source are projected. An ophthalmic apparatus according to any one of claims 1 to 6, further comprising a distance calculation unit that calculates the distance between the optical head and the eye under examination based on the captured image including the bright spot image and the image of the illumination light.

10. The ophthalmic apparatus according to claim 9, wherein the finite-distance illumination light source is a keratinizing light source.

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