JP7718930B2 - keratometry device - Google Patents

Description

The present invention relates to a corneal measurement device that measures the cornea of a subject's eye.

The keratometer (corneal curvature measurement device) described in Patent Document 1 projects a ring pattern of light from a keratinizing light source onto a 3 mm diameter position on the cornea of the subject's eye, and captures an image of the anterior segment of the eye by photographing the cornea. The keratometer then measures the corneal radius of curvature (corneal curvature) at a 3 mm diameter position on the cornea based on the ring pattern image, which is a reflected image of the ring pattern light detected from the anterior segment image. Note that, since curvature and radius of curvature are generally reciprocal, the corneal curvature and radius of curvature are equivalent.

The corneal topographer device (corneal shape measurement device) described in Patent Document 2 projects multiple concentric Placido ring lights onto the cornea from a Placido ring light source and photographs the cornea to obtain an image of the anterior segment. The corneal topographer device then detects a Placido ring image, which is a reflected image of the Placido ring lights, from the anterior segment image, and measures the corneal shape (corneal curvature distribution or corneal curvature radius distribution) of the cornea based on this Placido ring image.

Japanese Patent Application Laid-Open No. 2020-146095 Japanese Patent Application Laid-Open No. 2019-166277

The keratometer described in Patent Document 1 typically assumes that the corneal radius of curvature of the subject's eye is 8 mm, and adjusts the keratometer ring light source so that it can project a ring pattern light at a φ3 mm position on the cornea of the subject's eye. Therefore, if the actual corneal radius of curvature of the subject's eye deviates from 8 mm, it is not possible to project the ring pattern light from the keratometer ring light source at a φ3 mm position on the cornea. As a result, it is not possible to measure the corneal radius of curvature at a φ3 mm position on the cornea of the subject's eye. For this reason, there is a strong demand for the ability to freely adjust the position and shape of the ring pattern light projected onto the subject's eye. Similarly, there is a strong demand for the corneal topographer device described in Patent Document 2 to freely adjust the position and shape of the Placido ring light projected onto the subject's eye.

The present invention was made in consideration of these circumstances, and aims to provide a corneal measurement device that can arbitrarily adjust the position and shape of the pattern light projected onto the subject's eye.

A corneal measurement device that achieves the objectives of the present invention includes a dot matrix display that projects pattern light onto at least the cornea of the subject's eye and can arbitrarily change the shape of the pattern light, and an imaging optical system that captures the light returning from the subject's eye onto which the pattern light is projected by the display, and outputs an image of the anterior segment of the subject's eye.

This corneal measurement device uses a dot matrix display to project patterned light onto at least the cornea of the subject's eye, allowing the shape of this patterned light to be changed as desired, i.e., the projection position and shape of the patterned light projected onto the cornea can be changed as desired.

In another aspect of the corneal measurement device of the present invention, the display is a liquid crystal display.

A corneal measurement device according to another aspect of the present invention includes a corneal radius of curvature calculation unit that calculates the corneal radius of curvature of the subject's eye based on an anterior segment image output from the imaging optical system, and a first display control unit that controls the display based on the calculation results of the corneal radius of curvature calculation unit to correct the projection position of the ring pattern light onto the cornea to a predetermined target position. When the projection position of the ring pattern light is corrected by the first display control unit, the corneal radius of curvature calculation unit recalculates the corneal radius of curvature based on the anterior segment image output from the imaging optical system. This makes it possible to measure the corneal radius of curvature at a desired target position on the cornea of the subject's eye.

In a corneal measurement device according to another aspect of the present invention, the first display control unit calculates the angle of incidence of the ring pattern light with respect to the cornea that allows the ring pattern light to be incident on the target position based on the calculation result of the corneal curvature radius calculation unit and the target position, and corrects the projection position based on the calculation result of the angle of incidence. This makes it possible to measure the corneal radius of curvature at the desired target position on the cornea of the subject's eye.

In a corneal measurement device according to another aspect of the present invention, the first display control unit repeatedly corrects the projection position and the corneal radius of curvature calculation unit repeatedly recalculates the corneal radius of curvature. This makes it possible to measure the corneal radius of curvature at a desired target position on the cornea of the subject's eye.

In another aspect of the present invention, the corneal measurement device includes a second display control unit that controls the display to change the ring diameter of the ring pattern light projected onto the cornea multiple times by using a display controller; a first imaging control unit that causes the imaging optical system to capture images of the returning light for each ring diameter when the ring diameter is changed by the second display control unit; and a corneal shape calculation unit that calculates the corneal shape of the subject's eye based on anterior segment images captured by the imaging optical system for each ring diameter. This allows for more accurate measurement of the corneal shape of the subject's eye.

A corneal measurement device according to another aspect of the present invention includes a measurement head equipped with a display and an imaging optical system, a drive mechanism that moves the measurement head relative to the subject's eye along the optical axis direction of the imaging optical system, a second imaging control unit that causes the imaging optical system to capture images of returned light at multiple different imaging positions along the optical axis direction when the measurement head is moved relative to the subject's eye in the optical axis direction by the drive mechanism, and a corneal shape calculation unit that calculates the corneal shape of the subject's eye based on anterior segment images captured by the imaging optical system at each imaging position. This allows for more accurate measurement of the corneal shape of the subject's eye.

In a corneal measurement device according to another aspect of the present invention, the display has a display surface that displays a ring pattern, and is equipped with a third display control unit that applies anti-aliasing processing to the ring pattern displayed on the display surface, and the display projects, as pattern light, ring pattern light corresponding to the ring pattern that has been subjected to anti-aliasing processing onto the cornea. This ensures accuracy in measuring the corneal radius of curvature and corneal shape of the subject's eye, even when a low-resolution display is used.

In a corneal measurement device according to another aspect of the present invention, the display projects a grid-shaped pattern of light onto the cornea and includes a corneal shape calculation unit that calculates the corneal shape of the subject's eye based on the anterior segment image output from the imaging optical system. This allows the corneal radius of curvature or corneal shape of the subject's eye to be measured with higher accuracy.

In a corneal measurement device according to another aspect of the present invention, the display displays an illumination pattern for illuminating the anterior segment of the subject's eye, the illumination pattern having a larger area than the ring pattern used to measure the corneal radius of curvature or corneal shape of the subject's eye, and projects pattern light corresponding to the illumination pattern onto the anterior segment. This allows the display to double as an illumination light source, thereby reducing the number of parts in the corneal measurement device and achieving lower costs.

A corneal measurement device according to another aspect of the present invention includes a measurement head equipped with a display and an imaging optical system, and a drive mechanism for moving the measurement head relative to the subject's eye. The display is capable of projecting alignment light onto the cornea, which is used to align the measurement head with the subject's eye. The device also includes an alignment control unit that, when the alignment light is projected onto the cornea from the display, drives the drive mechanism based on an anterior segment image output from the imaging optical system to align the measurement head with the subject's eye. This allows the display to double as an alignment light source, thereby reducing the number of parts in the corneal measurement device and achieving cost savings. Furthermore, the shape and size of the alignment light can be adjusted as desired, improving the robustness of alignment detection.

In a corneal measurement device according to another aspect of the present invention, the display can project fixation light onto the subject's eye to fixate the eye. This allows the display to double as a fixation light source, reducing the number of components in the corneal measurement device and lowering costs. Furthermore, the light intensity, color, size, and position of the fixation light can be freely changed.

A corneal measurement device according to another aspect of the present invention includes an objective lens that transmits return light from the subject's eye and emits it to an imaging optical system, a cylindrical lens holder that houses the objective lens, and a through-hole formed in the display through which the lens holder passes, with the display fitted and fixed to the outside of the lens holder.

The present invention allows for arbitrary adjustment of the position and shape of the pattern light projected onto the subject's eye.

1 is a schematic diagram of a corneal measurement device according to a first embodiment. In FIG. 2, reference numeral 2A is a front view of the display surface of the dot matrix LCD as seen from the front side in the Z direction, and reference numeral 2B is an enlarged view of the area enclosed by a dotted circle C on the display surface. FIG. 1 is a front view of a cornea onto which ring pattern light is projected by a dot matrix LCD. 10A and 10B are explanatory diagrams illustrating modified examples of ring pattern light projected onto the cornea Ec from a dot matrix LCD. FIG. 2 is a functional block diagram of the control device according to the first embodiment. 10 is an explanatory diagram for explaining the relationship between the corneal curvature radius of the subject's eye, the incident angle of the ring pattern light to the cornea, and the projection position of the ring pattern light on the cornea. FIG. 10 is an explanatory diagram for explaining the shape correction of the ring pattern on the display surface by the height position calculation unit, more specifically, the correction of the height position of the ring pattern in the radial direction relative to the optical axis. FIG. 4 is a flowchart showing a flow of corneal curvature measurement of a subject's eye by the corneal measurement apparatus of the first embodiment. FIG. 10 is a functional block diagram of a control device of a corneal measurement apparatus according to a second embodiment. FIG. 10 is an explanatory diagram showing an example of a placido ring displayed on a dot matrix LCD according to a second embodiment. 10 is an explanatory diagram showing an example of a Placido ring light projected onto the cornea from the dot matrix LCD of the second embodiment. FIG. Reference numerals XIIA to XIIC are explanatory diagrams for explaining display control of a dot matrix LCD by an LCD control unit in a modification of the second embodiment. 13A to 13C are diagrams illustrating changes in the ring diameter of the ring pattern light projected onto the cornea in a modification of the second embodiment. 10 is a flowchart showing a procedure for measuring the corneal shape of the subject's eye in a modified example of the second embodiment. FIG. 11 is a functional block diagram of a control device of a corneal measurement apparatus according to a third embodiment. Reference symbols XVIA to XVIC are explanatory diagrams for explaining movement control of the measuring head by the movement control section. 11 is a flowchart showing a flow of corneal shape measurement of a subject's eye in the third embodiment. 10A and 10B are explanatory diagrams for explaining problems that arise when a ring pattern is displayed on a dot matrix LCD. 10 is an explanatory diagram for explaining display control of a ring pattern on a dot matrix LCD by an LCD control unit of a fourth embodiment. FIG. FIG. 11 is a front view of a display surface of a dot matrix LCD according to a fifth embodiment, as viewed from the front side in the Z direction. 13 is an explanation showing an example of a grating pattern light projected onto the cornea from a dot matrix LCD according to the fifth embodiment. 10A and 10B are explanatory diagrams for explaining problems that arise when a dot matrix LCD is used as an illumination light source for the anterior segment of a subject's eye. 23 is a front view of the dot matrix LCD in FIG. 22 as viewed from the front side in the Z direction. FIG. 13 is an explanatory diagram for explaining illumination of the anterior segment of the eye to be examined by a dot matrix LCD of the corneal measurement device of the sixth embodiment. 25 is a front view of the dot matrix LCD in FIG. 24 as viewed from the front side in the Z direction. FIG. 2 is a front view of the dot matrix LCD as seen from the front side in the Z direction. FIG. 10 is an explanatory diagram showing ring pattern light projected onto the cornea from a dot matrix LCD, and is a diagram for explaining the problems that arise when a dot matrix LCD is used as an alignment light source for aligning a measurement head with respect to a subject's eye. FIG. 10 is a front view of the dot matrix LCD as seen from the front side in the Z direction, showing a state in which a ring pattern for alignment is displayed on the display surface. 10 is an explanatory diagram showing alignment light projected onto the cornea Ec from a dot matrix LCD. FIG. FIG. 19 is a front view of an objective lens and a dot matrix LCD in a multifunction peripheral according to an eighth embodiment.

[First embodiment]
1 is a schematic diagram of a corneal measurement device 10 according to a first embodiment. Of the mutually orthogonal X, Y, and Z directions in the figure, the X direction is the left-right direction, the Y direction is the up-down direction, and the Z direction is the front-to-back direction (also referred to as the working distance direction) parallel to the front direction approaching the subject (subject's eye E) and the rear direction moving away from the subject.

As shown in FIG. 1, the corneal measurement device 10 of the first embodiment functions as a corneal curvature measurement device that measures the corneal radius of curvature (corneal curvature) at a predetermined target position (measurement position) on the cornea Ec of the subject's eye E, specifically at a position of φ3 mm (including approximately φ3 mm), and as a corneal shape measurement device that measures the corneal shape (corneal curvature distribution or corneal radius of curvature distribution) of the cornea Ec. Note that the first embodiment will be described using the corneal measurement device 10 as an example to measure the corneal radius of curvature of the subject's eye E.

<Overall configuration of the corneal measurement device>
The corneal measurement device 10 includes a measurement head 12, a drive mechanism 14, an operation unit 16, and a face support unit (not shown) that supports the face of the subject.

The measurement head 12, which will be described in more detail below, houses various optical systems and computing devices used to measure the corneal radius of curvature of the subject's eye E.

Although not shown, the drive mechanism 14 is composed of known actuators that move the measurement head 12 in each of the X, Y, and Z directions, and holds the measurement head 12 so that it can move freely in each of the X, Y, and Z directions. By driving the drive mechanism 14 under the control of the control device 30, which will be described later, or by driving the drive mechanism 14 in response to operation of the operation unit 16, which will be described later, it becomes possible to align the measurement head 12 in the X, Y, and Z directions with respect to the subject's eye E (hereinafter simply referred to as alignment).

The operation unit 16 accepts input for various operations of the corneal measurement device 10, such as an operation to start measurement of the corneal curvature radius of the subject's eye E, an operation to manually move the measurement head 12 in the X, Y, and Z directions, and an operation to set up the corneal measurement device 10.

The measurement head 12 includes a lens holder 20, a dot-matrix LCD (Liquid Crystal Display) 22, an objective lens 24, an imaging optical system 26, a monitor 28, and a control device 30.

The lens holder 20 is provided on the front surface of the measurement head 12 in the Z direction (toward the eye E to be examined) and is formed in a roughly cylindrical shape extending in the Z direction. An objective lens 24 is housed and held inside this lens holder 20. In addition, a dot matrix LCD 22 is fitted and fixed to the outside of the lens holder 20.

The dot matrix LCD 22, which will be described in more detail below, projects ring pattern light L1 onto the cornea Ec of the subject's eye E, which is used to measure the corneal curvature radius of the subject's eye E, and functions as a so-called keratin ring light source (Placido ring light source).

The objective lens 24 transmits the return light L2 from the cornea Ec onto which the ring pattern light L1 is projected by the dot matrix LCD 22, and emits it toward the imaging optical system 26. Note that the symbol O1 in the figure indicates the optical axis of the objective lens 24 and the imaging optical system 26.

The imaging optical system 26, not shown, includes one or more lenses, one or more apertures, and a complementary metal oxide semiconductor (CMOS) or charge coupled device (CCD) imaging element. The imaging optical system 26 captures the return light L2 incident from the objective lens 24 and outputs an anterior segment image D, which is an observation image of the anterior segment of the subject's eye E, to the control device 30.

Although not shown in Figure 1, an alignment optical system 27 (see Figure 5) is provided within the measurement head 12. The alignment optical system 27 projects alignment light onto the cornea Ec for aligning the measurement head 12 with the subject's eye E. The alignment optical system 27 is a known technology (see, for example, Patent Document 2 above), so a detailed description will be omitted here. Return light L2 from the subject's eye E (cornea Ec) onto which the alignment light is projected is imaged by the imaging optical system 26, and an anterior eye image D is input from this imaging optical system 26 to the control device 30.

Under the control of the control device 30 (described below), the monitor 28 displays an anterior segment image D of the subject's eye E, the measurement results of the corneal curvature radius of the subject's eye E, and the setting screen of the corneal measurement device 10.

The control device 30 comprehensively controls the operation of each part of the corneal measurement device 10 in response to input operations on the operation unit 16, and calculates the corneal radius of curvature of the subject's eye E based on the anterior segment image D input from the imaging optical system 26. Furthermore, as will be described in detail below, the control device 30 controls the projection of ring pattern light L1 onto the cornea Ec by the dot matrix LCD 22 in order to measure the corneal radius of curvature at a position of φ3 mm on the cornea Ec regardless of the assumed value (8 mm) of the corneal radius of curvature of the subject's eye E. Note that, although the control device 30 is provided inside the measurement head 12 in the first embodiment, the control device 30 may also be provided outside the measurement head 12.

<Dot matrix LCD>
2, reference numeral 2A is a front view of the display surface 22a of the dot matrix LCD 22 as seen from the front side in the Z direction (the side of the eye E to be examined), and reference numeral 2B is an enlarged view of the area of the display surface 22a (light exit surface) surrounded by a dotted circle C. Fig. 3 is a front view of the cornea Ec onto which the ring pattern light L1 is projected by the dot matrix LCD 22.

As shown by reference numerals 2A and 2B in Figure 2, the dot matrix LCD 22 is a monochrome LCD without a color filter and is equipped with an infrared LED (light emitting diode) as a backlight source, which emits infrared light (near-infrared light) with a wavelength of, for example, 940 nm. The dot matrix LCD 22 has a display surface 22a capable of displaying various patterns and a through-hole 22b through which the lens holder 20 described above passes.

The display surface 22a has a plurality of pixels 23 (dots) arranged two-dimensionally in the X and Y directions. Therefore, under the control of the control device 30, it is possible to display a pattern of any shape on the display surface 22a. As a result, by adjusting the position and shape of the pattern displayed on the display surface 22a, it is possible to arbitrarily change the projection position and shape of the pattern light projected from the dot matrix LCD 22 onto the cornea Ec. When measuring the corneal radius of curvature of the subject's eye E, the dot matrix LCD 22 displays a ring pattern LP on the display surface 22a under the control of the control device 30.

As shown in Figure 3, when a ring pattern LP is displayed on the display surface 22a, ring pattern light L1 corresponding to the ring pattern LP is emitted from the display surface 22a, and this ring pattern light L1 is projected onto the cornea Ec. By projecting ring pattern light L1 from the dot matrix LCD 22 onto the cornea Ec, it is possible to omit the light guide plate and diffusion plate provided in conventional keratin ring light sources, etc.

The shape of the ring pattern LP displayed on the display surface 22a, for example, the ring diameter, can be changed as desired. Therefore, by changing the ring diameter of the ring pattern LP displayed on the display surface 22a, the angle of incidence of the ring pattern light L1 from the dot matrix LCD 22 onto the cornea Ec can be changed as desired. As a result, the projection position of the ring pattern light L1 projected onto the cornea Ec (the ring diameter of the ring pattern light L1 on the cornea Ec) can be changed as desired (see Figures 6 and 7).

The ring diameter of the ring pattern LP initially displayed on the display surface 22a is adjusted to a size that allows the ring pattern light L1 to be projected at a position of φ3 mm on the cornea Ec of the subject's eye E, assuming the subject's eye E has a corneal radius of curvature of 8 mm. Under the control of the control device 30 (described below), the dot matrix LCD 22 corrects the ring diameter of the ring pattern LP on the display surface 22a so that the ring pattern light L1 can be projected at a position of φ3 mm on the cornea Ec even if the corneal radius of curvature of the subject's eye E deviates from the assumed value of 8 mm.

Figure 4 is an explanatory diagram illustrating a modified example of the ring light pattern L1 projected from the dot matrix LCD 22 onto the cornea Ec. In Figures 3 and 4 above, a continuous ring pattern LP is displayed on the display surface 22a, and continuous ring light pattern L1 is projected from this display surface 22a onto the cornea Ec. However, the shapes of the ring pattern LP and ring light pattern L1 are not particularly limited as long as the corneal radius of curvature of the subject's eye E can be measured. For example, although not shown, an intermittent ring pattern LP composed of multiple circular points may be displayed on the display surface 22a, and intermittent ring light pattern L1 may be projected from the display surface 22a onto the cornea Ec, as shown in Figure 4. The projection position (ring diameter) of this ring light pattern L1 can also be changed as desired.

<Control device>
FIG. 5 is a functional block diagram of the control device 30 according to the first embodiment. As shown in FIG. 5, the control device 30 includes an arithmetic circuit configured with various processors, memories, and the like. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). The various functions of the control device 30 may be implemented by a single processor or by multiple processors of the same or different types.

By executing a control program read from a storage unit (not shown), the control device 30 functions as an imaging control unit 32, an alignment control unit 34, a corneal curvature radius calculation unit 36, a monitor control unit 38, and an LCD control unit 40. Note that what is described as a "unit" of the control device 30 may also be a "circuit," a "device," or a "equipment." In other words, what is described as a "unit" may be composed of firmware, software, hardware, or a combination of these.

The imaging control unit 32 controls the imaging of the return light L2 by the imaging optical system 26. For example, when an operation to start measurement of the corneal radius of curvature is performed on the operation unit 16, the imaging control unit 32 causes the imaging optical system 26 to continuously (continuously) capture the return light L2 and output the anterior segment image D. As a result, during alignment, the anterior segment image D of the subject's eye E (cornea Ec) onto which alignment light is projected by the alignment optical system 27 is continuously output from the imaging optical system 26 to the control device 30. Furthermore, during corneal radius of curvature measurement, the anterior segment image D of the subject's eye E (cornea Ec) onto which ring pattern light L1 is projected by the dot matrix LCD 22 is continuously output from the imaging optical system 26 to the control device 30.

When aligning the measurement head 12 with the subject's eye E, the alignment control unit 34 controls the alignment optical system 27 to project alignment light onto the cornea Ec, and acquires anterior segment images D of the subject's eye E, which are continuously output from the imaging optical system 26. The alignment control unit 34 then detects the alignment of the measurement head 12 in the X, Y, and Z directions with respect to the subject's eye E, based on the anterior segment images D input from the imaging optical system 26. Note that specific alignment detection methods are well-known techniques, so a detailed description will be omitted. Next, the alignment control unit 34 drives the drive mechanism 14 to perform alignment in the X, Y, and Z directions based on the alignment detection results in the X, Y, and Z directions.

When measuring the corneal radius of curvature of the subject's eye E, the corneal radius of curvature calculation unit 36 detects a ring image corresponding to the ring pattern light L1 from the anterior segment image D output from the imaging optical system 26, and calculates the corneal radius of curvature of the subject's eye E using a known method based on the detection results of this ring image. This allows the corneal radius of curvature to be measured at the position on the cornea Ec where the ring pattern light L1 is projected (assumed position is φ3 mm).

In addition, the corneal curvature radius calculation unit 36 repeatedly recalculates the corneal curvature radius of the subject's eye E based on the new anterior segment image D output from the imaging optical system 26 each time the projection position of the ring pattern light L1 projected onto the cornea Ec is corrected by the LCD control unit 40 (described below).

The monitor control unit 38 controls the display on the monitor 28. At least during alignment and when measuring the corneal radius of curvature of the subject's eye E, the monitor control unit 38 causes the monitor 28 to display a moving image of the anterior segment image D based on the anterior segment image D continuously output from the imaging optical system 26. In addition, when the corneal radius of curvature calculation unit 36 calculates the corneal radius of curvature of the subject's eye E, the monitor control unit 38 causes the calculation result to be displayed on the monitor 28.

In the first embodiment, the LCD control unit 40 corresponds to the first display control unit of the present invention. This LCD control unit 40 operates when measuring the corneal radius of curvature of the subject's eye E, and controls the display of the ring pattern LP by the dot matrix LCD 22, i.e., controls the projection position (ring diameter) of the ring pattern light L1 projected from the dot matrix LCD 22 onto the cornea Ec.

Figure 6 is an explanatory diagram illustrating the relationship between the corneal radius of curvature of the test eye E, the angle of incidence of the ring pattern light L1 onto the cornea Ec, and the projection position of the ring pattern light L1 on the cornea Ec. As shown in Figure 6, if the corneal radius of curvature is "r," the angle of incidence of the ring pattern light L1 onto the cornea Ec (also called the angle of view) is "2θ," and the projection position of the ring pattern light L1 on the cornea Ec (height position from the optical axis O1 with the optical axis O1 as the reference) is "h" (2h = φ), these relationships can be expressed by the following equation (1):

As shown in Figures 5 and 6, the LCD control unit 40 first assumes that the corneal curvature radius of the subject's eye E is 8 mm, and sets a φ3 mm position on the cornea Ec of the subject's eye E as the target position. It then controls the angle of incidence of the ring pattern light L1 with respect to the cornea Ec, i.e., the shape of the ring pattern LP on the display surface 22a, so that the ring pattern light L1 is projected at the target position.

Specifically, based on the above formula (1), the LCD control unit 40 adjusts the radial height H (see FIG. 7) of the ring pattern LP within the display surface 22a so that the ring pattern light L1 is projected from the dot-matrix LCD 22 onto the cornea Ec at an incident angle (2θ) that achieves 2h(φ) = 3 mm, assuming r = 8 mm. This results in the projection of the ring pattern light L1 onto the cornea Ec by the dot-matrix LCD 22, the imaging optical system 26 capturing the returned light L2 and outputting the anterior segment image D, and the corneal radius of curvature calculation unit 36 calculating the corneal radius of curvature. If the actual corneal radius of curvature of the subject's eye E deviates from the assumed value (r = 8 mm), the corneal radius of curvature is measured at a position on the cornea Ec that deviates from 2h(φ) = 3 mm.

Next, the LCD control unit 40 uses the corneal radius of curvature calculation result obtained by the corneal radius of curvature calculation unit 36 to control the dot matrix LCD 22 to adjust the angle of incidence of the ring pattern light L1 relative to the cornea Ec so that the ring pattern light L1 is projected at a position of φ3 mm on the cornea Ec even if the corneal radius of curvature deviates from the expected value. Therefore, the LCD control unit 40 functions as an incident angle calculation unit 40a and a height position calculation unit 40b when measuring the corneal radius of curvature of the subject's eye E.

The incident angle calculation unit 40a calculates the incident angle (2θ) that achieves 2h(φ) = 3 mm using the above formula [1] based on the corneal curvature radius calculation result "r" by the corneal curvature radius calculation unit 36.

Figure 7 is an explanatory diagram illustrating the shape correction of the ring pattern LP on the display surface 22a by the height position calculation unit 40b, more specifically, the correction of the height position H of the ring pattern LP in the radial direction relative to the optical axis O1. Note that the reference numeral 25a in the figure denotes the aperture of the imaging optical system 26.

As shown in Figure 7 and the previously described Figures 5 and 6, the height position calculation unit 40b adjusts the shape (ring diameter) of the ring pattern LP on the display surface 22a based on the calculation result of the incident angle (2θ) by the incident angle calculation unit 40a, i.e., adjusts the height position H of the ring pattern LP in the radial direction (XY direction) relative to the optical axis O1, so that this incident angle is realized.

Specifically, if the distance in the Z direction between the corneal apex of the subject's eye E and the dot matrix LCD 22 is "D" (a known value), the distance in the Z direction between the corneal apex and the incident point Q of the ring pattern light L1 on the cornea Ec is "d" (see Figure 6), and the radial distance between the incident point Q and the optical axis O1 is "h," then the incident angle is expressed by the following equation (2):

Furthermore, "θ" in equation (2) is expressed by the following equation (3), and "d" is expressed by the following equation (4).

Here, "r" in the above [Equation 3] and [Equation 4] is the result of the calculation of the corneal radius of curvature by the corneal radius of curvature calculation unit 36, and "h" is a value that satisfies 2h = φ3 mm. Therefore, the height position calculation unit 40b can calculate the angle of incidence (2θ) that satisfies 2h = φ3 mm using the above [Equation 3]. The height position calculation unit 40b can also calculate "d" using the above [Equation 4]. The height position calculation unit 40b then substitutes the calculation results of "2θ" and "d" and the known values "D" and "h" into the following [Equation 5], which is a modification of the above [Equation 2], to calculate the height position (H) corresponding to the angle of incidence (2θ) that achieves 2h(φ) = 3 mm.

The LCD control unit 40 adjusts the ring diameter of the ring pattern LP displayed on the display surface 22a to the height position (H) based on the calculation result of the height position (H) by the height position calculation unit 40b. As a result, the ring pattern light L1 is projected from the dot matrix LCD 22 at an incident angle (2θ) that achieves 2h(φ) = 3 mm onto the cornea Ec, and the projection position of the ring pattern light L1 onto the cornea Ec is corrected to φ3 mm. Note that "correction of the projection position" here also includes correction of the shape of the ring pattern light L1 on the cornea Ec, i.e., correction of the ring diameter of the ring pattern light L1.

Once the projection position of the ring pattern light L1 on the cornea Ec is corrected by the LCD control unit 40, the imaging optical system 26 captures the return light L2 and outputs the anterior segment image D, and the corneal radius of curvature calculation unit 36 recalculates the corneal radius of curvature.

The following steps are repeated until the calculation result of the corneal radius of curvature by the corneal radius of curvature calculation unit 36 converges: correction of the projection position of the ring pattern light L1 by the LCD control unit 40; imaging of the returned light L2 by the imaging optical system 26 and output of the anterior segment image D; and recalculation of the corneal radius of curvature by the corneal radius of curvature calculation unit 36. When the calculation result of the corneal radius of curvature converges, the corneal radius of curvature calculation unit 36 confirms this value as the measurement result of the corneal radius of curvature of the subject's eye E. Note that the corneal radius of curvature calculation unit 36 may calculate the corneal radius of curvature using the above formula (1) based on the calculation result of the final incident angle (2θ) by the incident angle calculation unit 40a.

[Operation of the First Embodiment]
8 is a flowchart showing the flow of corneal curvature measurement of the subject's eye E using the corneal measurement device 10 of the first embodiment configured as described above. As shown in Fig. 8, after the subject's face is supported on a face support (not shown), the examiner performs a measurement start operation using the operation unit 16 (step S1). In response to this measurement start operation, the alignment optical system 27 projects alignment light onto the cornea Ec, the imaging optical system 26 captures the returned light L2 and outputs an anterior eye image D, and the alignment control unit 34 performs alignment in the X, Y, and Z directions.

Once alignment is complete, the LCD control unit 40 controls the dot matrix LCD 22 to display a ring pattern LP on the display surface 22a so that the ring pattern light L1 is projected at a position of φ3 mm on the cornea Ec of the subject's eye E, which has a corneal curvature radius of 8 mm (step S2). This causes the ring pattern light L1 to be projected from the dot matrix LCD 22 onto the cornea Ec (step S3), and the imaging optical system 26 continuously captures the return light L2 and outputs an anterior eye image D (step S4). The anterior eye image D output from the imaging optical system 26 is then input to the corneal curvature radius calculation unit 36 and the monitor control unit 38, and the monitor control unit 38 displays the anterior eye image D on the monitor 28.

Next, the corneal curvature radius calculation unit 36 calculates the corneal curvature radius at the projection position of the ring pattern light L1 on the cornea Ec based on the anterior eye image D input from the imaging optical system 26, and outputs the calculation result to the monitor control unit 38 and the incident angle calculation unit 40a (step S5). As a result, the monitor control unit 38 displays the calculation result of the corneal curvature radius of the subject's eye E on the monitor 28.

Furthermore, based on the calculation result of the corneal radius of curvature input from the corneal radius of curvature calculation unit 36, the incident angle calculation unit 40a recalculates the incident angle (2θ) of the ring pattern light L1 with respect to the cornea Ec using the above [Equation 1] so as to achieve 2h(φ) = 3 mm, and outputs the recalculation result to the height position calculation unit 40b (step S6).

Then, based on the result of the calculation of the incident angle (2θ) input from the incident angle calculation unit 40a, the height position calculation unit 40b calculates the radial height position (H) of the ring pattern LP using the above equations [2] to [5] so that this incident angle is realized (step S7).

Once the height position calculation unit 40b has completed calculation of the height position (H), the LCD control unit 40 controls the dot matrix LCD 22 based on the calculation results to correct the ring diameter of the ring pattern LP on the display surface 22a to the height position (H). As a result, the projection position (ring diameter) of the ring pattern light L1 onto the cornea Ec is corrected to a position of φ3 mm on the cornea Ec (step S8).

Once the correction of the projection position of the ring pattern light L1 is complete, the imaging optical system 26 again captures the return light L2 and outputs the anterior eye image D (step S9), and the corneal curvature radius calculation unit 36 recalculates the corneal curvature radius (step S10).

Then, the above-mentioned processes from step S6 to step S10 are repeated until the calculation result of the corneal radius of curvature by the corneal radius of curvature calculation unit 36 converges (step S11). Then, when the calculation result of the corneal radius of curvature converges, the corneal radius of curvature calculation unit 36 confirms that value as the measurement result of the corneal radius of curvature of the subject's eye E, or calculates the corneal radius of curvature using the above-mentioned [Equation 1] based on the final calculation result of the incident angle by the incident angle calculation unit 40a. Then, the measurement result of the corneal radius of curvature of the subject's eye E is displayed on the monitor 28 by the monitor control unit 38.

As described above, in the first embodiment, by projecting ring pattern light L1 from the dot matrix LCD 22 onto the cornea Ec, the projection position (including the shape such as the ring diameter) of the ring pattern light L1 projected onto the cornea Ec of the subject's eye E can be adjusted as desired. As a result, the corneal radius of curvature at the desired position (φ3 mm) on the cornea Ec can be measured regardless of the corneal radius of curvature of the subject's eye E.

In the first embodiment described above, the corneal measurement device 10 measures the corneal radius of curvature of the test eye E at a φ3 mm position on the cornea Ec. However, the present invention can also be applied to cases where an arbitrary position on the cornea Ec other than φ3 mm (e.g., φ1 mm, φ2 mm, φ4 mm, ...) is set as the target position and the corneal radius of curvature is measured at this target position.

Second Embodiment
9 is a functional block diagram of the control device 30 of the corneal measurement device 10 of the second embodiment. In the first embodiment, the corneal measurement device 10 is used to measure the corneal radius of curvature of the subject's eye E, but in the second embodiment, the corneal measurement device 10 is used to measure the corneal shape of the subject's eye E.

The corneal measurement device 10 of the second embodiment has basically the same configuration as the corneal measurement device 10 of the first embodiment, except that the LCD control unit 40 of the control device 30 has some different functions and the control device 30 functions as the corneal shape calculation unit 42. Therefore, parts that are the same in function or configuration as those of the first embodiment are given the same reference numerals and their description will be omitted.

Figure 10 is an explanatory diagram showing an example of the Placido ring LPM displayed on the dot matrix LCD 22 of the second embodiment. Figure 11 is an explanatory diagram showing an example of the Placido ring light L1M projected onto the cornea Ec from the dot matrix LCD 22 of the second embodiment.

As shown in FIG. 10 and the previously described FIG. 9, when a measurement operation for the corneal shape of the subject's eye E is performed using the operation unit 16, the LCD control unit 40 of the second embodiment controls the dot matrix LCD 22 to display the Placido ring LPM, which is a concentric and multiple (double or more) ring pattern LP, on the display surface 22a. As a result, as shown in FIG. 11, Placido ring light L1M, which is composed of concentric and multiple ring pattern light L1, is projected from the dot matrix LCD 22 onto the subject's eye E. Return light L2 from the cornea Ec onto which the Placido ring light L1M is projected is then incident on the imaging optical system 26 through the objective lens 24, and, as in the first embodiment, the imaging optical system 26 captures the return light L2 and outputs an anterior segment image D.

Returning to Figure 9, the corneal shape calculation unit 42 detects ring images corresponding to each ring pattern light L1 of the Placido ring light L1M from the anterior segment image D based on the anterior segment image D output from the imaging optical system 26 during corneal shape measurement of the subject's eye E, and calculates the corneal shape of the subject's eye E using a known method based on the detection results of each ring image. The calculation results of the corneal shape of the subject's eye E by the corneal shape calculation unit 42 are displayed on the monitor 28 by the monitor control unit 38.

As described above, in the second embodiment, the corneal shape of the subject's eye E can also be measured by projecting the Placido ring light L1M from the dot matrix LCD 22 onto the cornea Ec. Furthermore, simply by switching the pattern displayed on the dot matrix LCD 22, it is possible to switch between measuring the corneal radius of curvature and measuring the corneal shape of the subject's eye E, making it possible to switch between measuring the corneal radius of curvature and measuring the corneal shape easily and at low cost.

[Modification of the second embodiment]
In the second embodiment, the corneal shape of the subject's eye E is measured based on an anterior-segment image D obtained by projecting Placido ring light L1M from the dot-matrix LCD 22 onto the cornea Ec and capturing return light L2 from the cornea Ec using the imaging optical system 26. In this case, the smaller the pitch of each ring pattern light L1 constituting the Placido ring light L1M, the more accurately the corneal shape of the subject's eye E can be measured. However, if the pitch of each ring pattern light L1 is smaller than the resolving power (resolution) of the imaging optical system 26, the ring images cannot be detected accurately from the anterior-segment image D, resulting in a large measurement error in the corneal shape.

In this modified example of the second embodiment, each ring pattern light L1 constituting the Placido ring light L1M is projected onto the cornea Ec in sequence, i.e., projected onto the cornea Ec with a time difference, making it possible to accurately measure the corneal shape of the subject's eye E even if the pitch of each ring pattern light L1 is smaller than the resolving power of the imaging optical system 26. Note that the modified example of the second embodiment has basically the same configuration as the second embodiment described above, and therefore, components that are identical in function or configuration to the above embodiments are assigned the same reference numerals and their description will be omitted.

Reference symbols XIIA to XIIC in Figure 12 are explanatory diagrams illustrating display control of the dot matrix LCD 22 by the LCD control unit 40 in a modified example of the second embodiment. Reference symbols XIIIA to XIIIC in Figure 13 are explanatory diagrams illustrating changes in the ring diameter of the ring pattern light L1 projected onto the cornea Ec in a modified example of the second embodiment.

As shown by reference numerals XIIA to XIIC in Figure 12, the LCD control unit 40 of the second embodiment corresponds to the second display control unit of the present invention and controls the dot matrix LCD 22 in response to an operation to start corneal shape measurement using the operation unit 16 to display one ring pattern LP on the display surface 22a and change the ring diameter of this ring pattern LP multiple times. Specifically, the LCD control unit 40 sequentially changes the ring diameter of the ring pattern LP displayed on the display surface 22a to the ring diameter of each ring pattern LP that constitutes the desired Placido ring LPM. As a result, ring pattern light L1 with different ring diameters is projected sequentially onto the cornea Ec, as shown by reference numerals XIIIA to XIIIC in Figure 13.

In addition, if the ring diameter of each ring pattern light L1 projected from the dot matrix LCD 22 onto the cornea Ec, i.e., the projection position on the cornea Ec (e.g., φ1 mm, φ2 mm, φ3 mm, ...), is predetermined, correction similar to that in the first embodiment described above may be performed for each ring diameter (projection position) of the ring pattern light L1.

The imaging control unit 32 (corresponding to the first imaging control unit of the present invention) of the modified second embodiment controls the imaging optical system 26 to repeatedly capture the return light L2 from the cornea Ec by the imaging optical system 26 and output an anterior eye image D for each ring diameter of the ring pattern light L1 projected onto the cornea Ec. This allows an anterior eye image D corresponding to each ring diameter of the ring pattern light L1 to be obtained. These anterior eye images D are equivalent to the anterior eye image D of the subject's eye E in which the Placido ring light L1M shown in Figure 11 has been projected onto the cornea Ec.

The corneal shape calculation unit 42 detects ring images corresponding to the ring pattern light L1 from the anterior segment images D captured by the imaging optical system 26 for each different ring diameter of the ring pattern light L1, and calculates the corneal shape of the subject's eye E based on the detection results of the ring images in each anterior segment image D using a known method similar to that of the second embodiment described above.

Figure 14 is a flowchart showing the flow of corneal shape measurement of the subject's eye E in a modified example of the second embodiment. As shown in Figure 14, when the examiner performs a measurement start operation on the operation unit 16 (step S1), the previously described alignment is performed. Then, as with the corneal curvature measurement of the first embodiment shown in Figure 8, the following steps are performed: displaying a ring pattern LP on the dot matrix LCD 22 (step S2), projecting ring pattern light L1 from the dot matrix LCD 22 onto the cornea Ec (step S3), and capturing the return light L2 by the imaging optical system 26 and outputting an anterior segment image D (step S4).

At this time, the processing from step S5 to step S8, which is the same as that of the first embodiment shown in Figure 8, may be repeatedly executed to correct the projection position of the ring pattern LP projected from the dot matrix LCD 22 onto the cornea Ec to the desired target position.

Next, the LCD control unit 40 controls the dot matrix LCD 22 to change the ring diameter of the ring pattern LP displayed on the display surface 22a (YES in step S4A, step S4B). As a result, the ring pattern light L1 with the changed ring diameter is projected from the dot matrix LCD 22 onto the cornea Ec (step S3), and the imaging optical system 26 again captures the return light L2 and outputs the anterior eye image D (step S4).

The processes of steps S4B, S3, and S4 are repeated until the anterior eye image D has been captured for each of the ring pattern light L1 corresponding to all remaining ring diameters (NO in step S4A). This results in an anterior eye image D captured for each of the different ring diameters of the ring pattern light L1, i.e., an image equivalent to the anterior eye image D onto which the Placido ring light L1M is projected (YES in step S4A).

The corneal shape calculation unit 42 then detects a ring image corresponding to the ring pattern light L1 for each anterior segment image D, based on the anterior segment images D captured for each different ring diameter of the ring pattern light L1. Because each anterior segment image D contains only one ring image, it is possible to detect a ring image from each anterior segment image D regardless of the resolution of the imaging optical system 26. The corneal shape calculation unit 42 then calculates the corneal shape of the subject's eye E based on the detection results of the ring images from each anterior segment image D (step S5A). The calculation results of the corneal shape of the subject's eye E are displayed on the monitor 28 by the monitor control unit 38.

As described above, in the modified example of the second embodiment, the dot matrix LCD 22 is controlled to change the ring diameter of the ring pattern light L1 projected onto the subject's eye E, while the imaging optical system 26 captures anterior eye images D for each different ring diameter. This eliminates the need to detect multiple ring images from a single anterior eye image D. This allows for accurate detection of ring images from each anterior eye image D, even when the pitch of each ring pattern light L1 is smaller than the resolving power of the imaging optical system 26. As a result, it is no longer necessary to make the pitch of each ring pattern light L1 constituting the Placido ring light L1M larger than the resolving power of the imaging optical system 26, as in the second embodiment, and therefore the corneal shape of the subject's eye E can be measured more accurately than in the second embodiment.

[Third embodiment]
15 is a functional block diagram of the control device 30 of the corneal measurement device 10 of the third embodiment. In the modified example of the second embodiment, the ring diameter of the ring pattern LP displayed on the display surface 22a of the dot matrix LCD 22 is changed to obtain anterior eye images D captured for each of different ring diameters of the ring pattern light L1. However, in the third embodiment, the distance between the subject's eye E and the measurement head 12 is changed.

As shown in Figure 15, the corneal measurement device 10 of the third embodiment has basically the same configuration as the corneal measurement device 10 of each of the above embodiments, except that the control device 30 functions as the movement control unit 44 and the functions of the imaging control unit 32 and LCD control unit 40 are slightly different. Therefore, parts that are functionally or structurally identical to those of the above embodiments are given the same reference numerals and their description will be omitted.

Reference symbols XVIA to XVIC in Figure 16 are explanatory diagrams illustrating movement control of the measurement head 12 by the movement control unit 44. As shown in Figure 16 and the previously described Figure 15, the movement control unit 44 controls the drive mechanism 14 in response to an operation to start corneal shape measurement on the operation unit 16, and moves the measurement head 12 relative to the subject's eye E in the optical axis direction along the optical axis O1, i.e., in the Z direction. Note that although Figure 16 shows the measurement head 12 being moved from the subject side to the examiner side, it may also be moved from the examiner side to the subject side.

In the third embodiment, the LCD control unit 40 controls the dot matrix LCD 22 in response to the measurement start operation described above to display on the display surface 22a a ring pattern LP that can project ring pattern light L1 at a position, for example, φ3 mm (or a position other than 3 mm) on the cornea Ec. This causes the ring pattern light L1 to be projected from the dot matrix LCD 22 onto the cornea Ec. In this state, the drive mechanism 14 moves the measurement head 12 relative to the subject's eye E in the Z direction, changing the angle of incidence of the ring pattern light L1 incident on the cornea Ec from the dot matrix LCD 22. As a result, the ring diameter (projection position) of the ring pattern light L1 projected onto the cornea Ec can be changed in accordance with the relative movement of the measurement head 12 in the Z direction relative to the subject's eye E. Note that if it is not possible to project ring pattern light L1 of the desired ring diameter onto the cornea Ec simply by moving the measurement head 12 relative to the Z direction, the ring diameter of the ring pattern light L1 may be changed simultaneously as described in the modified example of the second embodiment above.

The imaging control unit 32 of the third embodiment (corresponding to the second imaging control unit of the present invention) causes the imaging optical system 26 to capture the return light L2 and output anterior segment images D at multiple imaging positions along the Z direction when the measurement head 12 is moved relative to the subject's eye E in the Z direction by the drive mechanism 14. As a result, as in the modified example of the second embodiment, anterior segment images D captured for each different ring diameter of the ring pattern light L1 are obtained. As a result, the corneal shape of the subject's eye E can be calculated by the corneal shape calculation unit 42.

Figure 17 is a flowchart showing the flow of corneal shape measurement of the subject's eye E in the third embodiment. As shown in Figure 17, when the examiner performs a measurement start operation on the operation unit 16 (step S1), alignment is performed in the same manner as in the modified example of the second embodiment described above (see Figure 14), and the measurement head 12 is positioned at the initial imaging position relative to the subject's eye E.

Once alignment is complete, the dot matrix LCD 22 displays the ring pattern LP (step S2), the dot matrix LCD 22 projects the ring pattern light L1 onto the cornea Ec (step S3), and the imaging optical system 26 captures the return light L2 and outputs the anterior segment image D (step S4).

Next, the movement control unit 44 drives the drive mechanism 14 to start moving the measurement head 12 in the Z direction relative to the test eye E (step S4C). Then, the imaging control unit 32 repeatedly controls the imaging optical system 26 to capture the return light L2 and output the anterior eye image D each time the drive mechanism 14 moves the measurement head 12 to the remaining imaging positions along the Z direction (step S4D, NO in step S4E). This results in an anterior eye image D captured for each different ring diameter of the ring pattern light L1, and is equivalent to the anterior eye image D projected with the Placido ring light L1M. Note that each time the measurement head 12 is moved to an imaging position, the LCD control unit 40 may simultaneously change the ring diameter of the ring pattern light L1 projected onto the cornea Ec, if necessary.

When the imaging optical system 26 has completed capturing the return light L2 at all imaging positions, the movement control unit 44 stops the relative movement of the measurement head 12 by the drive mechanism 14 (YES in step S4E). Next, the corneal shape calculation unit 42 calculates the corneal shape of the subject's eye E based on the anterior segment images D of the ring pattern light L1 with different ring diameters, as in the modified example of the second embodiment described above (step S5A).

As described above, in the third embodiment, the measurement head 12 is moved relative to the test eye E in the Z direction while the imaging optical system 26 captures images of the return light L2 at multiple imaging positions along the Z direction, thereby achieving the same effect as the modified example of the second embodiment.

In the third embodiment described above, the measurement head 12 is moved in the Z direction by the drive mechanism 14, but for example, a face support unit (not shown) may be moved in the Z direction, and the method of moving the measurement head 12 relative to the subject's eye E in the Z direction is not particularly limited.

[Fourth embodiment]
Fig. 18 is an explanatory diagram for explaining a problem that occurs when the ring pattern LP is displayed on the dot matrix LCD 22. Note that reference numeral XVIIIA in Fig. 18 is a front view of the display surface 22a of the dot matrix LCD 22 as viewed from the front side in the Z direction (the side of the eye E to be examined), and reference numeral XVIIIB is an enlarged view of the area surrounded by the dotted circle D1 on the display surface 22a.

In each of the above embodiments (except for the second embodiment), a ring pattern LP is displayed on the display surface 22a of the dot matrix LCD 22, and ring pattern light L1 is projected from the dot matrix LCD 22 onto the cornea Ec. In this case, as shown by symbols XVIIIA and XVIIIB in Figure 18, if the resolution of the dot matrix LCD 22 is low, jaggies will occur in the ring pattern LP displayed on the display surface 22a, i.e., in the ring pattern light L1 projected onto the cornea Ec. As a result, the accuracy with which the corneal curvature radius calculation unit 36 detects the ring image from the anterior eye image D will decrease, and the accuracy with which the corneal curvature radius (keratomileus value) of the subject's eye E will also decrease.

The required accuracy for the corneal radius of curvature (keratomileusis value) specified by the ISO (International Organization for Standardization) is ±0.03 mm. For example, in the previously mentioned Figures 6 and 7, if D = 65 mm, 2h = 3 mm, and r = 10 mm, then H = 41.14 mm. However, if "H" deviates by approximately 0.12 mm, "r" will be measured with a deviation of 0.03 mm. For this reason, the resolution of the dot matrix LCD 22 must be sufficiently smaller than 0.12 mm; however, for example, the resolution of the dot matrix LCD 22 used in each of the above embodiments is 0.18 mm, which is lower than 0.12 mm.

In the corneal measurement device 10 of the fourth embodiment, the resolution of the ring pattern LP displayed on the dot matrix LCD 22 is artificially increased so that measurement accuracy of the corneal curvature radius (keratomileusis value) of the subject's eye E can be ensured even when a low-resolution dot matrix LCD 22 is used. The corneal measurement device 10 of the fourth embodiment has basically the same configuration as the corneal measurement devices 10 of the above embodiments, except for some differences in the function of the LCD control unit 40. Therefore, components that are the same in function or configuration as those of the above embodiments are assigned the same reference numerals and their description will be omitted.

Figure 19 is an explanatory diagram illustrating display control of the ring pattern LP on the dot matrix LCD 22 by the LCD control unit 40 of the fourth embodiment. Note that reference symbol XIXA in Figure 19 is a front view of the display surface 22a of the dot matrix LCD 22 as seen from the front side in the Z direction (the side of the subject's eye E), and reference symbol XIXB is an enlarged view of the area surrounded by the dotted circle D2 on the display surface 22a.

As shown in FIG. 19, the LCD control unit 40 of the fourth embodiment corresponds to the third display control unit of the present invention. This LCD control unit 40 performs anti-aliasing processing (also known as smoothing processing) on the ring pattern LP displayed on the display surface 22a of the dot matrix LCD 22, for example, by placing intermediate color (intermediate gradation) dots at the boundaries of the ring pattern LP. This reduces (makes less noticeable) the jaggedness of the ring pattern LP, thereby virtually increasing the resolution of the ring pattern LP displayed on the display surface 22a, i.e., the ring pattern light L1 projected from the dot matrix LCD 22 onto the cornea Ec. For example, if the resolution of the ring pattern LP is reduced from 0.18 mm to 0.045 mm, which is one-fourth of that, the required accuracy of the corneal radius of curvature (keratomileusis value) specified by the ISO mentioned above is met.

As described above, in the fourth embodiment, by applying anti-aliasing processing to the ring pattern LP displayed on the dot matrix LCD 22, it is possible to ensure the accuracy of measuring the corneal radius of curvature of the subject's eye E even when a low-resolution dot matrix LCD 22 is used.

In the second embodiment, when the Placido ring LPM is displayed on the display surface 22a of the dot matrix LCD 22, anti-aliasing processing may be applied to the Placido ring LPM, as in the fourth embodiment.

Fifth Embodiment
Fig. 20 is a front view of the display surface 22a of the dot-matrix LCD 22 of the fifth embodiment, as seen from the front side in the Z direction (the side of the test eye E). Fig. 21 illustrates an example of a grating pattern light L3 projected onto the cornea Ec from the dot-matrix LCD 22 of the fifth embodiment. In each of the above embodiments, the dot-matrix LCD 22 projects a ring pattern light L1 or a Placido ring light L1M onto the cornea Ec. However, as described in the fourth embodiment, the occurrence of jaggies in the ring pattern light L1 may reduce the detection accuracy of the ring image from the anterior eye image D (such as due to fluctuations in the center of gravity of the ring image). Therefore, the corneal measurement device 10 of the fifth embodiment is capable of projecting a pattern light having a different shape from that of each of the above embodiments onto the cornea Ec from the dot-matrix LCD 22.

The corneal measurement device 10 of the fifth embodiment has basically the same configuration as the corneal measurement device 10 of each of the above embodiments, except for some differences in the functionality of the LCD control unit 40. Therefore, parts that are the same in function or configuration as the above embodiments are given the same reference numerals and their description will be omitted.

As shown in FIG. 20, the LCD control unit 40 of the corneal measurement device 10 of the fifth embodiment controls the dot matrix LCD 22 to display a grid pattern GP, which is a grid-like pattern, in response to an operation to start measurement of the corneal radius of curvature or corneal shape using the operation unit 16. As a result, as shown in FIG. 21, grid pattern light L3 corresponding to the grid pattern GP is projected from the dot matrix LCD 22 onto the cornea Ec. Return light L2 from the cornea Ec onto which the grid pattern light L3 is projected enters the imaging optical system 26 through the objective lens 24, and the imaging optical system 26 captures the return light L2 and outputs an anterior eye image D.

The corneal radius of curvature calculation unit 36 or corneal shape calculation unit 42 of the fifth embodiment detects a pattern image corresponding to the grating pattern light L3 from the anterior segment image D based on the anterior segment image D output from the imaging optical system 26, and calculates the corneal radius of curvature or corneal shape of the subject's eye E using a known method based on the detection results of this pattern image.

As described above, in the fifth embodiment, by making it possible to project grid pattern light L3 onto the cornea Ec from the dot matrix LCD 22, it is possible to measure the corneal radius of curvature or corneal shape of the test eye E with higher accuracy than when ring pattern light L1 is projected onto the cornea Ec.

The shape of the pattern light projected from the dot matrix LCD 22 onto the cornea Ec is not limited to the examples shown in the above embodiments and can be modified as appropriate, as long as it is possible to measure the corneal radius of curvature or corneal shape of the subject's eye E.

Sixth Embodiment
Fig. 22 is an explanatory diagram for explaining the problem when the dot matrix LCD 22 is used as an illumination light source for the anterior segment of the subject's eye E. Fig. 23 is a front view of the dot matrix LCD 22 in Fig. 22 as seen from the front side in the Z direction (the subject's eye E side).

As shown in Figures 22 and 23, it is possible to use a dot matrix LCD 22 as an illumination light source to illuminate the anterior segment of the subject's eye E in the corneal measurement device 10. However, in this case, there is a risk that the amount of light provided by the ring pattern light L1 (corneal curvature measurement device) or the Placido ring light L1M (corneal shape measurement device) may be insufficient.

In the corneal measurement device 10 of the sixth embodiment, the display of the display surface 22a is controlled so that the dot matrix LCD 22 also functions as an illumination light source. The corneal measurement device 10 of the sixth embodiment has essentially the same configuration as the corneal measurement devices 10 of the above embodiments, except for a partial difference in the function of the LCD control unit 40. Therefore, components that are identical in function or configuration to those of the above embodiments are assigned the same reference numerals and their description will be omitted.

Figure 24 is an explanatory diagram illustrating illumination of the anterior segment of the subject's eye E by the dot matrix LCD 22 of the corneal measurement device 10 of the sixth embodiment. Figure 25 is a front view of the dot matrix LCD 22 in Figure 24 as viewed from the front side in the Z direction (the side of the subject's eye E).

24 and 25, when an operation to start illuminating the anterior segment of the subject's eye E is performed on the operation unit 16, the LCD control unit 40 of the sixth embodiment controls the dot matrix LCD 22 to display an illumination pattern IP for illuminating the anterior segment of the subject's eye E on the display surface 22a. This illumination pattern IP is displayed on the display surface 22a by the LCD control unit 40 so that its display area is larger than that of the ring pattern LP (corneal curvature measurement device) or the Placido ring LPM (corneal shape measurement device). As a result, illumination pattern light L4 corresponding to the illumination pattern IP is projected from the dot matrix LCD 22 onto the anterior segment (cornea Ec) of the subject's eye E. Because the light intensity of this illumination pattern light L4 is greater than that of the ring pattern light L1 or the Placido ring light L1M, the anterior segment of the subject's eye E can be illuminated with the illumination pattern light L4.

The shape of the illumination pattern IP is not particularly limited as long as it has a larger display area on the display surface 22a than the ring pattern LP or the Placido ring LPM. For example, the illumination pattern IP may be expanded to cover the entire surface (including substantially the entire surface) of the display surface 22a, and the illumination pattern light L4 may be projected onto the anterior segment of the subject's eye E from the entire surface of the display surface 22a.

As described above, in the sixth embodiment, the illumination pattern light L4 can be projected from the dot matrix LCD 22 onto the anterior segment of the subject's eye E, allowing the dot matrix LCD 22 to also serve as an illumination light source. As a result, the number of components in the corneal measurement device 10 can be reduced, leading to lower costs.

Seventh Embodiment
Fig. 26 is a front view of the dot matrix LCD 22 as seen from the front side in the Z direction (the side of the subject's eye E). Fig. 27 is an explanatory diagram showing the ring pattern light L1 projected from the dot matrix LCD 22 onto the cornea Ec, and is a diagram for explaining problems that arise when the dot matrix LCD 22 is used as an alignment light source for aligning the measurement head 12 with the subject's eye E.

In each of the above embodiments, alignment is performed by the alignment control unit 34 by projecting alignment light from the alignment optical system 27 onto the cornea Ec, but in the corneal measurement device 10 of the seventh embodiment, alignment is performed using a dot matrix LCD 22 instead of the alignment optical system 27.

In this case, as shown in Figures 26 and 27, if the ring pattern light L1 projected from the dot matrix LCD 22 onto the cornea Ec falls on the iris or edge of the iris of the subject's eye E, it becomes difficult to detect the ring image corresponding to this ring pattern light L1 from the anterior segment image D, which may reduce alignment accuracy. For this reason, in the corneal measurement device 10 of the seventh embodiment, the dot matrix LCD 22 is controlled to adjust the shape of the ring pattern light L1 projected onto the cornea Ec so that the ring image corresponding to the ring pattern light L1 can be easily detected from the anterior segment image D.

The corneal measurement device 10 of the seventh embodiment has basically the same configuration as the corneal measurement device 10 of each of the above embodiments, except for some differences in the functions of the LCD control unit 40 and the alignment control unit 34. Therefore, parts that are the same in function or configuration as the above embodiments are given the same reference numerals and their description will be omitted.

Figure 28 is a front view of the dot matrix LCD 22 as seen from the front side in the Z direction (toward the subject's eye E), showing the state in which the alignment ring pattern LA is displayed on the display surface 22a. Figure 29 is an explanatory diagram showing the alignment light L5 projected from the dot matrix LCD 22 onto the cornea Ec.

As shown in Figures 28 and 29, the LCD control unit 40 of the seventh embodiment controls the dot matrix LCD 22 during alignment to display a ring pattern LA for XY alignment on the display surface 22a, and projects alignment light L5 corresponding to this ring pattern LA from the dot matrix LCD 22 onto the cornea Ec.

At this time, the ring diameter of the ring pattern LA displayed on the display surface 22a is adjusted to a size such that the alignment light L5 emitted from the dot matrix LCD 22 is projected onto the inside of the iris of the subject's eye E, i.e., onto the pupil. For example, in the seventh embodiment, the ring diameter of the ring pattern LA is formed to be smaller than the ring diameter of the ring pattern LP used to measure the corneal radius of curvature. This prevents the alignment light L5 from impinging on the iris or iris edge of the subject's eye E. Then, return light L2 from the cornea Ec onto which the alignment light L5 is projected enters the imaging optical system 26 through the objective lens 24, and the imaging optical system 26 captures the return light L2 and outputs an anterior segment image D.

The alignment control unit 34 of the seventh embodiment detects the alignment of the measurement head 12 in the X and Y directions relative to the subject's eye E based on the anterior eye image D input from the imaging optical system 26, and drives the drive mechanism 14 based on the alignment detection results to perform alignment in the X and Y directions.

Although not shown, an alignment pattern for Z alignment may be displayed on the display surface 22a of the dot matrix LCD 22, and Z alignment light corresponding to this alignment pattern may be projected onto the cornea Ec. In this case, the imaging optical system 26 also captures the returned light L2 and outputs the anterior segment image D. The alignment control unit 34 then detects the Z-direction alignment of the measurement head 12 with respect to the subject's eye E based on the anterior segment image D input from the imaging optical system 26, and drives the drive mechanism 14 based on the alignment detection results to perform Z-direction alignment.

As described above, in the seventh embodiment, by making it possible to project alignment light L5 from the dot matrix LCD 22 onto the cornea Ec, the dot matrix LCD 22 can also be used as the alignment optical system 27. As a result, the alignment optical system 27 can be omitted from the corneal measurement device 10, reducing the number of components in the corneal measurement device 10 and achieving cost reductions. Furthermore, since the shape and size of the alignment light L5 can be adjusted as desired, the robustness of alignment detection can be improved.

Eighth Embodiment
Figure 30 is a front view of the objective lens 24 and dot-matrix LCD 22 of the multifunction device 9 of the eighth embodiment. While the dot-matrix LCD 22 is provided in the corneal measurement device 10 in each of the above embodiments, in the eighth embodiment, as shown in Figure 30, the dot-matrix LCD 22 is provided in the multifunction device 9. The multifunction device 9 of the eighth embodiment combines the corneal measurement device 10 of each of the above embodiments with an optical coherence tomography (OCT) device that obtains a tomographic image of the subject's eye E using optical coherence tomography (OCT). The multifunction device 9 has basically the same configuration as the corneal measurement device 10 of each of the above embodiments, except that the measurement head 12 includes a well-known optical system for OCT measurement. Therefore, components that are identical in function or configuration to those of the above embodiments are designated by the same reference numerals, and their description will be omitted.

When OCT measurement (tomographic imaging) of the subject's eye E is performed using the multifunction device 9, fixation is performed to examine the desired area of the subject's eye E. This fixation is achieved by emitting fixation light toward the subject's eye E and having the subject's eye E gaze at this fixation light. In addition to internal fixation, in which fixation light is projected onto the subject's eye E through the objective lens 24, peripheral fixation and external fixation are also known as such fixations (see, for example, JP 2020-138002 A).

Peripheral fixation is a fixation method in which the subject's eye E is rotated significantly in the desired direction by selectively illuminating multiple fixation holes (fixation lights) arranged around the objective lens 24. External fixation is performed using an external fixation light, and by adjusting the position of the light source of the external fixation light, the subject's eye can be rotated in any direction, or rotated more significantly than with internal fixation, or the direction of the subject's eye E can be adjusted by guiding the gaze of the subject's eye E or fellow eye when internal fixation is not possible. The multifunction device 9 of the eighth embodiment performs peripheral fixation using the dot matrix LCD 22.

When peripheral fixation of the subject's eye E is performed, the LCD control unit 40 of the eighth embodiment controls the dot matrix LCD 22 in response to a selection operation input to the operation unit 16, selectively lighting up eight (or a number other than eight) fixation areas 50 that are arranged to surround the objective lens 24 on the display surface 22a and correspond to conventional fixation holes. As a result, fixation light is projected onto the subject's eye E from the lit fixation areas 50, and peripheral fixation is performed.

Furthermore, if the display area of the display surface 22a of the dot matrix LCD 22 is large, the fixation area 50 can be illuminated at any position on the display surface 22a (a position specified by the operation unit 16), and external fixation can be performed by projecting this fixation area 50 onto the subject's eye E.

Note that the ring pattern light L1 projected onto the cornea Ec from the dot matrix LCD when measuring the corneal radius of curvature or corneal shape is infrared light, but the fixation light used to fixate the subject's eye E is visible light. For this reason, in the eighth embodiment, it is preferable to use a dot matrix LCD 22 that can switch between emitting infrared light and visible light, for example, a dot matrix LCD 22 equipped with two types of LEDs: an infrared LED and a white LED.

As described above, in the eighth embodiment, fixation light can be projected from the dot matrix LCD 22 onto the subject's eye E, so the dot matrix LCD 22 can also be used as a fixation light source (fixation hole, external fixation light). As a result, the fixation light source can be omitted from the multifunction device 9, reducing the number of components in the multifunction device 9 and achieving cost reduction. Furthermore, by using the dot matrix LCD 22 as a fixation light source, the light intensity, color, size, position, etc. of the fixation light can be changed as desired.

In the above eighth embodiment, an all-in-one device 9 was described as combining an optical coherence tomography device with a corneal measurement device 10, but the present invention can also be applied to an all-in-one device 9 that combines various ophthalmic devices that perform visual fixation of the subject's eye E, such as a fundus camera, with a corneal measurement device 10.

[others]
In each of the above embodiments, various types of light are projected onto the subject's eye E from the dot matrix LCD 22, but various types of light may also be projected onto the subject's eye E using a known dot matrix display such as an organic EL (Electro Luminescence) display or a micro LED display that integrates only LEDs without using liquid crystal.

In the above embodiments, the corneal measurement device 10 has been described as a keratometer, a corneal topographer, or a combination device such as a keratometer. However, the present invention can also be applied to, for example, a corneal endothelial cell imaging device (specular microscope) or a combination device thereof that irradiates the cornea Ec with slit light and receives reflected light from the corneal endothelial cells of the cornea Ec to image the corneal endothelial cells.

9 Multifunction device 10 Corneal measurement device 12 Measurement head 14 Drive mechanism 16 Operation unit 20 Lens holding unit 22 Dot matrix LCD
22a Display surface 22b Through hole 23 Pixel 24 Objective lens 26 Imaging optical system 27 Alignment optical system 28 Monitor 30 Control device 32 Imaging control unit 34 Alignment control unit 36 Corneal curvature radius calculation unit 38 Monitor control unit 40 LCD control unit 40a Incident angle calculation unit 40b Height position calculation unit 42 Corneal shape calculation unit 44 Movement control unit 50 Fixation area C Dotted circle D Anterior eye segment images D1, D2 Dotted circle E Test eye Ec Cornea GP Grating pattern H Height position L1 Ring pattern light L1M Placido ring light L2 Return light L3 Grating pattern light L4 Illumination pattern light L5 Alignment light LA Ring pattern LC Dot matrix LP Ring pattern LPM Placido ring O1 Optical axis

Claims (15)

a dot matrix display that projects pattern light onto at least the cornea of the subject's eye and is capable of arbitrarily changing the shape of the pattern light;
an imaging optical system that captures an image of return light from the subject's eye onto which the pattern light is projected by the display, and outputs an image of an anterior segment of the subject's eye;
a first display control unit that controls the display based on the anterior eye image output from the imaging optical system so that a projection position of the pattern light is set to a predetermined target position of the cornea;
A corneal measurement device comprising: The corneal measurement device of claim 1, wherein the display is a liquid crystal display. a corneal curvature radius calculation unit that calculates a corneal curvature radius of the subject's eye based on the anterior eye image output from the imaging optical system,
3. The corneal measurement device according to claim 1, wherein the first display control unit controls the display based on the calculation result of the corneal curvature radius calculation unit to correct the projection position of the pattern light on the cornea to the target position. 4. The corneal measurement device according to claim 3, wherein the corneal radius of curvature calculation unit recalculates the corneal radius of curvature based on the anterior eye image output from the imaging optical system when the projection position of the pattern light is corrected by the first display control unit. a dot matrix display that projects pattern light onto at least the cornea of the subject's eye and is capable of arbitrarily changing the shape of the pattern light;
an imaging optical system that captures an image of return light from the subject's eye onto which the pattern light is projected by the display, and outputs an image of an anterior segment of the subject's eye;
Equipped with
the pattern light is a ring pattern light,
a corneal curvature radius calculation unit that calculates a corneal curvature radius of the subject's eye based on the anterior eye image output from the imaging optical system;
a first display control unit that controls the display based on a calculation result of the corneal curvature radius calculation unit to correct a projection position of the ring pattern light on the cornea to a predetermined target position;
Equipped with
a corneal radius of curvature calculation unit that recalculates the corneal radius of curvature based on the anterior segment image output from the imaging optical system when the projection position of the ring pattern light is corrected by the first display control unit. 6. The corneal measurement device according to claim 4, wherein the first display control unit calculates an incident angle of the pattern light with respect to the cornea that allows the pattern light to be incident on the target position based on the calculation result of the corneal radius of curvature calculation unit and the target position, and corrects the projection position based on the calculation result of the incident angle. The corneal measurement device according to claim 4 , wherein correction of the projection position by the first display control unit and recalculation of the corneal radius of curvature by the corneal radius of curvature calculation unit are repeatedly performed. the pattern light is a ring pattern light,
a second display control unit that controls the display to change a ring diameter of the ring pattern light projected onto the cornea a plurality of times;
a first imaging control unit that, when the ring diameter is changed by the second display control unit, causes the imaging optical system to capture an image of the returned light for each of the ring diameters;
a corneal shape calculation unit that calculates a corneal shape of the subject's eye based on the anterior eye image captured by the imaging optical system for each ring diameter;
The corneal measurement device according to claim 1 , further comprising: a measurement head including the display and the imaging optical system;
a drive mechanism that moves the measurement head relative to the subject's eye along the optical axis of the imaging optical system;
a second imaging control unit that causes the imaging optical system to capture images of the return light at a plurality of imaging positions that are different from each other along the optical axis when the measurement head is moved relative to the eye to be examined in the optical axis direction by the drive mechanism; and
a corneal shape calculation unit that calculates a corneal shape of the subject's eye based on the anterior eye image captured by the imaging optical system at each imaging position;
The corneal measurement device according to claim 1 , further comprising: the display has a display surface that displays a ring pattern;
a third display control unit that performs anti-aliasing processing on the ring pattern displayed on the display surface;
The corneal measurement device according to claim 1 , wherein the display projects, as the pattern light, a ring pattern light corresponding to the ring pattern that has been subjected to the anti-aliasing process onto the cornea. the display projects the grid-shaped pattern light onto the cornea;
5. The corneal measurement device according to claim 1, further comprising a corneal shape calculation unit that calculates a corneal shape of the subject's eye based on the anterior eye image output from the imaging optical system. 12. The corneal measurement device according to claim 1, wherein the display displays an illumination pattern for illuminating an anterior segment of the subject's eye, the illumination pattern having an area larger than that of a ring pattern used to measure the corneal radius of curvature or the corneal shape of the subject's eye, and projects the pattern light corresponding to the illumination pattern onto the anterior segment. a measurement head including the display and the imaging optical system;
a drive mechanism that moves the measurement head relative to the eye to be examined;
Equipped with
the display is capable of projecting alignment light used for aligning the measurement head with respect to the subject's eye onto the cornea;
13. The corneal measurement device according to claim 1, further comprising an alignment control unit that, when the alignment light is projected from the display onto the cornea, drives the drive mechanism based on the anterior eye image output from the imaging optical system to align the measurement head with the subject's eye. The corneal measurement device according to any one of claims 1 to 13 , wherein the display is capable of projecting fixation light onto the subject's eye to cause the subject's eye to fixate the eye. an objective lens that transmits the return light from the subject's eye and outputs the return light to the imaging optical system;
a cylindrical lens holding portion that houses the objective lens;
a through hole formed in the display and through which the lens holding portion passes;
Equipped with
The corneal measurement device according to any one of claims 1 to 14 , wherein the display is fitted and fixed to the outside of the lens holding portion.