Portable-type ocular refractivity measurement device

Abstract

A portable-type ocular refractivity measurement device 100 is provided with: a first cylindrical part 10 provided with a visual target 20 which can be visually recognized in the longitudinal direction (X direction) through the inside thereof; a second cylindrical part 30 which can slide and move in the longitudinal direction (X direction) with respect to the first cylindrical part 10 and is provided with a lens 40, and in which the visual target 20 can be visually recognized in the longitudinal direction (X direction) through the lens 40 and the inside thereof; and a scale 70 for measuring refractivity and provided on a lateral surface of the first cylindrical part 10 or the second cylindrical part 30.

Description

Portable eye refractive power measuring device

[0001] The present invention relates to a portable eye refractive power measuring device.

[0002] A measuring device for measuring the refractive power of an eye is known (for example, see Patent Document 1).

[0003] US Patent Application Publication No. 2015 / 0245764

[0004] However, the eye refractive power measuring device described in Patent Document 1 still has room for improvement in terms of easily measuring refractive power.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to make it possible to measure refractive power easily.

[0006] The present invention is a portable eye refractive power measuring device comprising: a first cylindrical portion having a visual target that can be viewed from the inside in the longitudinal direction; a second cylindrical portion that can be slid in the longitudinal direction relative to the first cylindrical portion, has a lens provided therein, and the visual target can be viewed from the inside in the longitudinal direction and through the lens; and a scale that is provided on the side of the first cylindrical portion or the second cylindrical portion and is used to measure refractive power.

[0007] In the above configuration, the second cylindrical portion can be slidably moved in the longitudinal direction relative to the first cylindrical portion inside the first cylindrical portion, the scale can be provided on the side surface of the second cylindrical portion, and the first cylindrical portion can be configured to have a window at the end of the side surface facing the second cylindrical portion through which the scale can be viewed.

[0008] In the above configuration, the first tube portion may have the visual target at one end and the other end open, and the second tube portion may have the lens at one end on the first tube portion side.

[0009] In the above configuration, when the first tube portion and the second tube portion are slid to their longest length, the visual target is at the position of the focal length of the lens, and the focal length of the lens can be configured to be 80 mm or more and 120 mm or less.

[0010] In the above configuration, when the first tube portion and the second tube portion are slid to their longest length, the distance between the visual target and the lens can be longer than the focal length of the lens.

[0011] In the above configuration, the first tube portion may have a first portion and a second portion that is slidable relative to the first portion and that has the target provided thereon.

[0012] In the above configuration, a movement suppressing member that suppresses movement of the first cylindrical portion relative to the second cylindrical portion may be provided between the first cylindrical portion and the second cylindrical portion.

[0013] In the above configuration, the movement suppressing member may be configured to extend in the longitudinal direction.

[0014] In the above configuration, the first cylindrical portion and the second cylindrical portion may be configured as polygonal prisms.

[0015] In the above configuration, the visual target may be configured as a pattern in which a plurality of black lines and a plurality of white lines are arranged alternately, the plurality of black lines having two or more different widths, and the plurality of white lines having two or more different widths.

[0016] According to the present invention, refractive power can be easily measured.

[0017] FIGS. 1(a) and 1(b) are cross-sectional views of a portable eye refraction measurement device according to Example 1. FIG. 2 is a diagram illustrating the optical principle of the portable eye refraction measurement device according to Example 1. FIGS. 3(a) and 3(b) are side views of the portable eye refraction measurement device according to Example 1. FIG. 4(a) is a bottom view of the portable eye refraction measurement device according to Example 1, FIG. 4(b) is a cross-sectional view taken along line A-A in FIG. 3(b), and FIG. 4(c) is a perspective side view of the interior of a first cylindrical portion. FIGS. 5(a) and 5(b) are side views of a portable eye refraction measurement device according to a modified example of Example 1. FIG. 6 is a diagram illustrating an example of an optotype. FIGS. 7(a) to 7(c) are cross-sectional views of a portable eye refraction measurement device according to Example 2. FIG. 8(a) is a cross-sectional view of the portable eye refraction measurement device according to Example 1 when it is at its shortest length, and FIG. 8(b) is a cross-sectional view of the portable eye refraction measurement device according to Example 2 when it is at its shortest length. 9A to 9C are cross-sectional views of a portable eye refractive power measuring device according to a modified example of the second embodiment.

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] 1(a) and 1(b) are cross-sectional views of a portable eye refractive power measuring device 100 according to Example 1. As shown in Fig. 1(a) and 1(b), the portable eye refractive power measuring device 100 includes a first cylindrical portion 10 and a second cylindrical portion 30.

[0020] The first cylindrical portion 10 is long in the X direction, has a hollow interior 16, is open at one end 12 in the X direction, and has a bottom 18 at the other end 14. A visual target 20 is provided on the surface of the bottom 18 facing the hollow 16. Therefore, when looking at only the first cylindrical portion 10, the visual target 20 can be seen from the open end 12 through the hollow 16.

[0021] The second cylindrical portion 30 is long in the X direction, has a hollow interior 36, has a transparent member 39 such as a glass member at one end 32 in the X direction, and has a bottom 38 at the other end 34. A lens 40 is provided in the bottom 38 so as to penetrate the bottom 38. The lens 40 is, for example, a monoconvex lens, but may also be a biconvex lens.

[0022] The second cylindrical portion 30 is inserted into the cavity 16 of the first cylindrical portion 10 from the bottom 38 side, and the first cylindrical portion 10 and the second cylindrical portion 30 are slidable relative to each other in the X direction. Compared to Fig. 1(a), Fig. 1(b) shows a case where the first cylindrical portion 10 slides in the +X direction relative to the second cylindrical portion 30. The first cylindrical portion 10 and the second cylindrical portion 30 are arranged coaxially in the X direction.

[0023] The subject places his / her eye 60 on the end 32 of the second tube portion 30 and looks inside, thereby being able to see the target 20 through the lens 40. That is, light 50 from the target 20 reaches the retina 62 via the lens 40 and the crystalline lens 64.

[0024] FIG. 1A shows the state where the first tube portion 10 is slid the furthest in the −X direction relative to the second tube portion 30, resulting in the longest combined length of the first tube portion 10 and the second tube portion 30. At this time, the visual target 20 is set to be located at a position corresponding to the focal length f1 of the lens 40. That is, the distance L1 between the visual target 20 and the lens 40 is set to be the focal length f1 of the lens 40. In this case, light 50 emitted from a point light source on the visual target 20 is converted into approximately parallel light by the lens 40 before reaching the crystalline lens 64, where it is converted into convergent light to form a focal point 66. When the subject's eye 60 is emmetropic, the focal point 66 is near the retina 62. The light 50 is, for example, light emitted from the visual target 20 when external light is irradiated onto the visual target 20; however, the visual target 20 itself may emit light.

[0025] 1(b) shows a case where the first tube portion 10 is slid relative to the second tube portion 30 in the +X direction, so that the distance L1 between the visual target 20 and the lens 40 becomes shorter than the focal length f1. In this case, the light 50 emitted from the point light source of the visual target 20 becomes slightly diffused light even after passing through the lens 40, and enters the crystalline lens 64 in this diffused state. Therefore, the convergent light converted by the crystalline lens 64 has a longer distance to the focal point 66 than in FIG. 1(a). If the subject's eye 60 is myopic, the focal point 66 will be near the retina 62.

[0026] In the second cylindrical portion 30, the distance L2 between the lens 40 and the end 32 is approximately equal to the focal length f1 of the lens 40, and for example, the distance L2 is 90% to 100% of the focal length f1.

[0027] Here, the optical principle of the portable eye refraction measurement device 100 will be described. Fig. 2 is a diagram showing the optical principle of the portable eye refraction measurement device 100 according to the first embodiment. Fig. 2 is a diagram showing the left-right reverse of Figs. 1(a) and 1(b). The dashed line in Fig. 2 represents light 50 emitted from the point light source of the eye target 20 when the eye target 20 is located at the focal length f1 of the lens 40. The dotted line represents light 50 emitted from the point light source of the eye target 20 when the eye target 20 is moved by δ1 toward the front from the focal length f1 of the lens 40.

[0028] As shown in FIG. 2, if the focal length of the lens 40 is f1, the focal length of the crystalline lens 64 is f2, and the distance between the crystalline lens 64 and the lens 40 is d, then the focal length f of the composite lens system formed by the lens 40 and the crystalline lens 64 is f = (f1 × f2) / (f1 + f2 - d). If the focal length f1 of the lens 40 is equal to the distance d, then f = d = f1. That is, even if the focal length f2 of the crystalline lens 64 changes, the position of the visual target 20 changes, but the NA of the light 50 emitted from the point light source of the visual target 20 remains constant. Therefore, δ1 = δ2. δ1 has the relationship δ1 = (d × f) / f2. Therefore, for example, if d = f1 = 100 mm and f2 = 200 mm (equivalent to a diopter value of -5D), δ1 is 50 mm.

[0029] 1(a) and 1(b), consider a case where the focal length f1 of the lens 40 is 100 mm, and the subject slides the first tube portion 10 in the +X direction relative to the second tube portion 30 to align the visual target 20 to a position where it appears normal (in focus). In this case, the diopter value changes by −1D every time the first tube portion 10 moves 10 mm in the +X direction relative to the second tube portion 30. Therefore, by measuring the position of the first tube portion 10 relative to the second tube portion 30, the diopter value (refractive power) of the subject's eye 60 can be measured.

[0030] Here, calculations were made to determine the relationship between the minimum and maximum lengths of the portable eye refractive power measuring device and the range of movement of the visual target 20 when measuring diopter values ​​from approximately 0D to -10D when the focal length f1 of the lens 40 was changed to 50mm, 100mm, and 200mm. Table 1 shows the calculation results when the focal length f1 of the lens 40 was 50mm.

[0031] In Table 1, D is the diopter value of the eye 60. f2 is the focal length of the crystalline lens 64 corresponding to the diopter value. f1 is the focal length of the lens 40. d is the distance between the lens 40 and the crystalline lens 64. f is the focal length of the composite lens system formed by the lens 40 and the crystalline lens 64. δ1 is the distance the visual target 20 is moved (see also FIG. 2 for f2, f1, d, and δ1). As described above, the distance d between the lens 40 and the crystalline lens 64 and the focal length f1 of the lens 40 are the same value. In this case, the focal length f of the composite lens system is the same value as the focal length f1 of the lens 40. Furthermore, when the first tube portion 10 is slid in the -X direction relative to the second tube portion 30 so as to be the longest, the distance between the lens 40 and the visual target 20 is also the same value as the focal length f1 of the lens 40. This also applies to Tables 2 and 3 below.

[0032] As shown in Table 1, when the focal length f1 of the lens 40 is 50 mm, the diopter value is −1×10 －８ The moving distance δ1 when D is 2.5 × 10 －８ mm, and the movement distance δ1 when the diopter value is -10D is 25 mm. In other words, a diopter value in the range of 0D to -10D can be measured within a range of 25 mm movement of the first tube portion 10 relative to the second tube portion 30. Since the maximum distance between the visual target 20 and the lens 40 is 50 mm, the same as the focal length f1 of the lens 40, it is possible to measure a diopter value up to -20D within the 50 mm range in which the first tube portion 10 can move maximum relative to the second tube portion 30. On the other hand, the diopter value changes by -4D for every 10 mm of movement. Therefore, when the focal length f1 of the lens 40 is 50 mm, it is difficult to measure the diopter value accurately.

[0033] Table 2 shows the calculation results when the focal length f1 is 200 mm.

[0034] As shown in Table 2, when the focal length f1 of the lens 40 is 200 mm, the diopter value is −1×10 －８ When D, the moving distance δ1 is 4 × 10 －７ mm, and the movement distance δ1 when the diopter value is −10 D is 400 mm. Because the maximum movement distance of the first tube portion 10 relative to the second tube portion 30 is 200 mm, the diopter value can only be measured in the range of 0 D to −5 D. Although it is required that the diopter value can be measured in the range of 0 D to −10 D, this is not satisfied when the focal length f1 of the lens 40 is 200 mm.

[0035] Table 3 shows the calculation results when the focal length f1 is 100 mm.

[0036] As shown in Table 3, when the focal length f1 of the lens 40 is 100 mm, the diopter value is −1×10 －８ When D is reached, the moving distance δ1 is 1×10 －７ mm, and the movement distance δ1 when the diopter value is -10D is 100 mm. Because the maximum movement distance of the first tube portion 10 relative to the second tube portion 30 is 100 mm, diopter values ​​from 0D to -10D can be measured within the maximum movement range of the first tube portion 10 relative to the second tube portion 30. In this case, the diopter value changes by -1D for every 10 mm of movement of the first tube portion 10 relative to the second tube portion 30, which is preferable in terms of measuring the diopter value with high accuracy. Furthermore, the minimum length of the portable eye refractive power measuring device is 100 mm, and the maximum length is 200 mm, which is also preferable in terms of portability and operability.

[0037] 3(a) and 3(b) are side views of the portable eye refractive power measurement device 100 according to Example 1. As shown in Fig. 3(a) and 3(b), the portable eye refractive power measurement device 100 is provided with a scale 70 for measuring refractive power on the side surface of the second tube portion 30. The scale 70 indicates, for example, a diopter value.

[0038] As described above, the diopter value of the subject's eye 60 changes depending on the position of the first tube portion 10 relative to the second tube portion 30, and therefore the diopter value of the subject's eye 60 can be measured by reading the graduations of the scale 70 at the end 12 of the first tube portion 10. That is, the subject looks into the interior of the second tube portion 30 from the end 32 of the second tube portion 30 and slides the first tube portion 10 in the +X direction relative to the second tube portion 30 until the optotype 20 provided on the first tube portion 10 looks normal. The diopter value of the subject's eye 60 can be measured by reading the graduations of the scale 70 at the end 12 of the first tube portion 10 at that time.

[0039] A window 72 through which the scale 70 can be read is provided on the side surface at the end 12 of the first cylindrical portion 10. This makes it easier to read the graduations of the scale 70 at the end 12 of the first cylindrical portion 10. The window 72 may be a gap formed by a notch provided in the end 12, or may be covered with a transparent member such as glass.

[0040] Fig. 4(a) is a bottom view of the portable eye refractive power measurement device 100 according to Example 1, Fig. 4(b) is a cross-sectional view taken along line A-A in Fig. 3(b), and Fig. 4(c) is a perspective side view of the inside of the first tube portion 10. As shown in Figs. 4(a) and 4(b), the first tube portion 10 and the second tube portion 30 have a polygonal prism shape, for example, a hexagonal prism shape. This prevents the portable eye refractive power measurement device 100 from rolling on a desk or the like. Furthermore, rotation of the second tube portion 30 relative to the first tube portion 10 is also prevented.

[0041] The second cylindrical portion 30 has a flange 35 at its end 32 opposite the first cylindrical portion 10 (see also FIGS. 3(a) and 3(b)). The flange 35 has a circular shape that is larger than that of the first cylindrical portion 10. Therefore, when the first cylindrical portion 10 is slid in the +X direction to abut against the flange 35 and shortened for carrying or the like, the flange 35 protrudes from the first cylindrical portion 10. This makes it easy to pull the first cylindrical portion 10 in the -X direction the next time it is used.

[0042] A movement suppressing member 80 is provided on the inner surface of the first cylindrical portion 10. That is, the movement suppressing member 80 is provided on the sliding surface between the first cylindrical portion 10 and the second cylindrical portion 30. The movement suppressing member 80 is a member for suppressing unintended movement of the first cylindrical portion 10 in the X direction relative to the second cylindrical portion 30. As shown in FIG. 4( c ), the movement suppressing member 80 is provided linearly on the inner surface of the first cylindrical portion 10 extending in the X direction. This suppresses unintended movement of the first cylindrical portion 10 in the X direction relative to the second cylindrical portion 30, regardless of the position of the first cylindrical portion 10 relative to the second cylindrical portion 30. The movement suppressing member 80 may be formed of felt, a leaf spring that presses against the second cylindrical portion 30, or some other type of member.

[0043] Although the example shows a case where two movement suppressing members 80 are provided at each corner of the hexagonal prism of the first tubular portion 10, the present invention is not limited to this case and may alternatively include a case where one movement suppressing member is provided at the center of each side of the hexagonal prism, or other cases. Furthermore, the movement suppressing member 80 does not necessarily extend linearly from end 12 to end 14 of the first tubular portion 10 and may have an interruption along the way. The movement suppressing member 80 may also be provided on the outer surface of the second tubular portion 30.

[0044] 5(a) and 5(b) are side views of a portable eye refractive power measuring device 110 according to a modified example of Example 1. In Example 1, as shown in Figures 3(a) and 3(b), an example has been shown in which the first tube portion 10 slides outside the second tube portion 30. However, this is not limiting, and the first tube portion 10 may slide inside the second tube portion 30, as shown in Figures 5(a) and 5(b). In this case, a scale 70 may be provided on the first tube portion 10.

[0045] As described above, according to Example 1 and its modified examples, as shown in FIGS. 1( a) and 1(b), the optotype 20 is provided on the first tube portion 10. The second tube portion 30 is slidable in the longitudinal direction (X direction) relative to the first tube portion 10 and is provided with a lens 40. The subject can visually recognize the optotype 20 on the first tube portion 10 through the interior of the second tube portion 30 and the lens 40. As shown in FIGS. 3( a) and 3(b) or FIGS. 5(a) and 5(b), a scale 70 for measuring refractive power is provided on the side of the first tube portion 10 or the side of the second tube portion 30. The subject looks through the second tube portion 30, sees the optotype 20, and slides the first tube portion 10 to a position where the optotype 20 appears normal (in focus). The subject's refractive power can be measured by reading the graduations on the scale 70 at this time, making it easy to measure refractive power. Furthermore, since the subject himself / herself slides and moves the first tube portion 10 to adjust the position where the target 20 is in focus, the subject can perform the measurement of his / her own volition, which also leads to improved measurement accuracy.

[0046] When measuring the refractive power, the first tube part 10 is slid to a position where the target 20 is first focused, and then further slid to a position just before the target 20 becomes unfocused, and the refractive power can be easily measured at two positions.

[0047] 3( a) and 3(b), in the first embodiment, the second cylindrical portion 30 slides inside the first cylindrical portion 10 in the longitudinal direction relative to the first cylindrical portion 10. The scale 70 is provided on the side surface of the second cylindrical portion 30, and the first cylindrical portion 10 has a window 72 through which the scale 70 can be seen on the side surface at the end 12 on the second cylindrical portion 30 side. The provision of the window 72 makes it possible to easily read the graduations of the scale 70. The second cylindrical portion 30, on which the lens 40 is provided, slides inside the first cylindrical portion 10, thereby achieving a simple structure.

[0048] 1(a) and 1(b), the first tube portion 10 has a visual target 20 at one end 14 and an open end 12. The second tube portion 30 has a lens 40 at one end 34 on the first tube portion 10 side. This allows the portable eye refractive power measuring device 100 to be made smaller, improving portability.

[0049] In Example 1 and its modified examples, as shown in FIG. 1A, when the first tube portion 10 and the second tube portion 30 are slid to their longest positions, the visual target 20 is located at the focal length f1 of the lens 40. The focal length f1 of the lens 40 is 80 mm or more and 120 mm or less. This allows for accurate measurement of refractive power, as described above. The device is also excellent in terms of portability and operability. From the viewpoints of accurate measurement of refractive power, portability, and operability, the focal length f1 of the lens 40 is preferably 90 mm or more and 110 mm or less, more preferably 95 mm or more and 105 mm or less, and most preferably 100 mm.

[0050] 4(b) and 4(c), in Example 1 and its modified examples, a movement suppression member 80 that suppresses movement of the first tube portion 10 relative to the second tube portion 30 is provided between the first tube portion 10 and the second tube portion 30. This suppresses unintentional movement of the first tube portion 10 after the subject slides the first tube portion 10 to a position where the visual target 20 is in focus, thereby enabling accurate measurement of refractive power.

[0051] 4C, in the first embodiment and its modified examples, the movement suppression member 80 is provided to extend in the longitudinal direction of the first cylindrical portion 10. This makes it possible to suppress unintentional movement of the first cylindrical portion 10 regardless of the position of the first cylindrical portion 10 relative to the second cylindrical portion 30.

[0052] In the first embodiment and its modified examples, the first cylindrical portion 10 and the second cylindrical portion 30 are polygonal prisms, as shown in Fig. 4(b), which prevents the first cylindrical portion 10 and the second cylindrical portion 30 from rolling on a desk or the like. Also, the first cylindrical portion 10 and the second cylindrical portion 30 are prevented from rotating relative to each other.

[0053] FIG. 6 is a diagram showing an example of the optotype 20. As shown in FIG. 6, the optotype 20 may be a design in which a plurality of black lines 21 and a plurality of white lines 22 are alternately arranged, and the plurality of black lines 21 and the plurality of white lines 22 have two or more different widths. By using such an optotype 20, it becomes easier for the subject to determine whether the optotype 20 is in focus or out of focus and appears blurry. It also becomes possible to measure the subject's visual acuity. Note that the optotype 20 may be a design other than that used in a general autorefractometer (e.g., a balloon, etc.).

[0054] While Example 1 has been described for measuring myopia, Example 2 will describe a case where both hyperopia and myopia are measured. Figures 7(a) to 7(c) are cross-sectional views of a portable eye refractive power measurement device 200 according to Example 2. Figure 7(a) shows the measurement position when the subject's eye 60 is hyperopic, Figure 7(b) shows the measurement position when the subject's eye 60 is emmetropic, and Figure 7(c) shows the measurement position when the subject's eye 60 is myopic. In Example 1, the first tube portion 10 and the second tube portion 30 had approximately the same length in the X direction, but in Example 2, the first tube portion 10 is longer in the X direction than the second tube portion 30.

[0055] 7(b), in the measurement position for emmetropia, the optotype 20 is located at a position corresponding to the focal length f1 of the lens 40. That is, the distance L1 between the optotype 20 and the lens 40 is equal to the focal length f1 of the lens 40. In this case, light 50 emitted from the point light source of the optotype 20 is converted into approximately parallel light by the lens 40, reaches the crystalline lens 64, and is converted into convergent light by the crystalline lens 64 to form a focal point 66. When the subject's eye 60 is emmetropic, the focal point 66 is located near the retina 62.

[0056] As shown in Figure 7(c) , from the state shown in Figure 7(b) , the first tube portion 10 is slid in the +X direction relative to the second tube portion 30 to make the distance L1 between the visual target 20 and the lens 40 shorter than the focal length f1. In this case, the light 50 emitted from the point light source of the visual target 20 becomes slightly diffused light even after passing through the lens 40, and enters the crystalline lens 64 in this diffused state. Therefore, the convergent light converted by the crystalline lens 64 has a longer distance to the focal point 66 than in Figure 7(b) . If the subject's eye 60 is myopic, the focal point 66 will be near the retina 62.

[0057] As shown in Figure 7(a), from the state shown in Figure 7(b), the first tube portion 10 is slid in the -X direction relative to the second tube portion 30 to make the distance L1 between the visual target 20 and the lens 40 longer than the focal length f1. In this case, light 50 emitted from the point light source of the visual target 20 becomes slightly convergent light after passing through the lens 40, and enters the crystalline lens 64 in the convergent light state. Therefore, the convergent light converted by the crystalline lens 64 has a shorter distance to the focal point 66 than in Figure 7(b). If the subject's eye 60 is farsighted, the focal point 66 will be near the retina 62.

[0058] In this way, both myopia and hyperopia can be measured by sliding the first tube portion 10 in the +X direction or the −X direction relative to the second tube portion 30 from the measurement position for normal vision.

[0059] Here, assuming that the focal length f1 of the lens 40 is 100 mm, the length of the first tube portion 10 in the X direction is 130 mm, and the length of the second tube portion 30 in the X direction is 100 mm, the results of calculations regarding the relationship between the minimum and maximum lengths of the portable eye refractive power measuring device 200 and the movement distance of the visual target 20 when measuring diopter values ​​from +3D to -7D are shown in Table 4.

[0060] In Table 4, similarly to Table 1 and the like described above, D is the diopter value of the eye 60, f2 is the focal length of the crystalline lens 64 corresponding to the diopter value, and f1 is the focal length of the lens 40. d is the distance between the lens 40 and the crystalline lens 64, f is the focal length of the composite lens system formed by the lens 40 and the crystalline lens 64, and δ1 is the distance by which the visual target 20 is moved in the +X direction or the −X direction from the measurement position for normal vision in FIG. 7(b).

[0061] As shown in Table 4, when the focal length f1 of the lens 40 is 100 mm, the movement distance δ1 in the −X direction when the diopter value is +3D is 30 mm (denoted as −30 mm), and the movement distance δ1 in the +X direction when the diopter value is −7D is 70 mm (denoted as +70 mm). Because the distance L2 between the lens 40 and the end 32 of the second tube portion 30 is approximately equal to the focal length f1 of the lens 40, the total distance that the first tube portion 10 can move relative to the second tube portion 30 is 100 mm in both the +X and −X directions. This is because if an attempt is made to move the end 12 of the first tube portion 10 in the +X direction beyond the end 32 of the second tube portion 30, the first tube portion 10 will hit the subject's face and will not be able to move. Therefore, the measurement range of the diopter value D is +3D to −7D. In this case, the diopter value changes by ±1D every time the first cylindrical portion 10 moves 10 mm relative to the second cylindrical portion 30, so the diopter value can be measured with high precision.

[0062] 7A, when the first tube portion 10 and the second tube portion 30 are slid to their longest positions, the distance L1 between the target 20 and the lens 40 is longer than the focal length f1 of the lens 40. This allows for measurement of hyperopia in addition to myopia.

[0063] FIG. 8( a) is a cross-sectional view of the portable eye refraction measurement device 100 according to Example 1 when it is at its shortest length, and FIG. 8( b) is a cross-sectional view of the portable eye refraction measurement device 200 according to Example 2 when it is at its shortest length. In Example 1, as shown in FIG. 1( a), the measurement position for emmetropia is reached when the first tube portion 10 slides to the furthest position relative to the second tube portion 30 in the −X direction. In this case, the lengths of the first tube portion 10 and the second tube portion 30 in the X direction are approximately equal, so that almost the entire second tube portion 30 can be stored inside the first tube portion 10, as shown in FIG. 8( a). This prevents the device from becoming too large and improves portability. On the other hand, in Example 2, as shown in FIG. 7( a), the measurement position for hyperopia is reached when the first tube portion 10 slides to the furthest position relative to the second tube portion 30 in the −X direction. In this case, as shown in FIG. 8( b), the device becomes larger by the amount that the first tube portion 10 is lengthened to measure the hyperopia side. Therefore, there is room for improvement in terms of portability.

[0064] 9(a) to 9(c) are cross-sectional views of a portable eye refractive power measuring device 210 according to a modified example of Example 2. Fig. 9(a) shows the measurement position when the subject's eye 60 is hyperopic, Fig. 9(b) shows the measurement position when the subject's eye 60 is emmetropic, and Fig. 9(c) shows the measurement position when the subject is myopic.

[0065] 9( a) to 9(c), in a modified example of Example 2, the first tube portion 10 includes a first portion 10a that slides in the X direction relative to the second tube portion 30, and a second portion 10b that slides in the X direction relative to the first portion 10a. The optotype 20 is provided in the second portion 10b. An opening 17 is provided at the bottom of the first portion 10a. A transparent member such as glass may be provided in the opening 17. The subject can look into the inside of the second tube portion 30 and see the optotype 20 through the lens 40 and the opening 17.

[0066] As shown in Figure 9(b), at the measurement position for normal vision, the second portion 10b of the first tube portion 10 slides in the +X direction to the maximum extent within the range of movement possible in the +X direction relative to the first portion 10a. In other words, the bottom 18b of the second portion 10b is in contact with the first portion 10a. Therefore, the first tube portion 10 is in its shortest state. At this time, the visual target 20 is located at the focal length f1 of the lens 40. In other words, the distance L1 between the visual target 20 and the lens 40 is the focal length f1 of the lens 40.

[0067] As shown in Figure 9(a), when measuring hyperopia, the second part 10b of the first tube part 10 is slid in the -X direction relative to the first part 10a from the state shown in Figure 9(b) so that the distance L1 between the visual target 20 and the lens 40 becomes longer than the focal length f1.

[0068] As shown in Fig. 9(c), when measuring myopia, the first portion 10a of the first tube portion 10 is slid together with the second portion 10b in the +X direction relative to the second tube portion 30 from the state shown in Fig. 9(b) so that the distance L1 between the visual target 20 and the lens 40 becomes shorter than the focal length f1. Because the first tube portion 10 has a sliding structure of the first portion 10a and the second portion 10b, it is possible to reduce the protrusion of the first tube portion 10 from the second tube portion 30 in the X direction, as in Example 1 shown in Fig. 8(a). This prevents the device from becoming too large and improves portability.

[0069] Furthermore, in Example 2, in the myopia measurement shown in FIG. 7( c), even if the end 12 of the first tube portion 10 is moved in the +X direction from the end 32 of the second tube portion 30, the first tube portion 10 cannot be moved because it would hit the subject's face. Therefore, the position shown in FIG. 8( b) is the limit position for myopia measurement. In this case, the myopia measurement range is narrower than in Example 1. On the other hand, in the modified example of Example 2, the visual target 20 can be brought closer to the lens 40 as shown in FIG. 9( c), so a myopia measurement range equivalent to that of Example 1 can be obtained.

[0070] As described above, in the modified example of Example 2, the first tube portion 10 has the first portion 10a and the second portion 10b, which is slidable relative to the first portion 10a and has the optotype 20 provided thereon. This prevents the device from becoming too large and improves portability. Furthermore, even when hyperopia measurement is possible, the myopia measurement range can be prevented from becoming narrower.

[0071] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0072] 10...first tube portion, 10a...first part, 10b...second part, 12...end, 14...end, 16...cavity, 17...opening, 18, 18b...bottom, 20...target, 21...black line, 22...white line, 30...second tube portion, 32...end, 34...end, 35...flange portion, 36...cavity, 38...bottom, 39...transparent member, 40...lens, 50...light, 60...eye, 62...retina, 64...crystalline lens, 66...focus, 70...scale, 72...window, 80...movement suppressing member, 100, 110, 200, 210...portable eye refractive power measuring device

Claims

1. A portable eye refractive power measuring device comprising: a first tube portion having a visual target that can be viewed from inside from the longitudinal direction; a second tube portion that can slide in the longitudinal direction relative to the first tube portion, has a lens provided therein, and can view the visual target from the longitudinal direction through the lens; and a scale provided on a side surface of the first tube portion or the second tube portion for measuring refractive power.

2. A portable eye refractive power measuring device as described in claim 1, wherein the second tube portion is inside the first tube portion and is slidable in the longitudinal direction relative to the first tube portion, the scale is provided on a side surface of the second tube portion, and the first tube portion has a window at the end of the side surface facing the second tube portion through which the scale can be viewed.

3. A portable eye refractive power measuring device as described in claim 1 or 2, wherein the first tube portion has the visual target provided at one end and the other end is open, and the second tube portion has the lens provided at one end on the first tube portion side.

4. A portable eye refractive power measuring device as described in claim 3, wherein when the first tube portion and the second tube portion are slid to their longest, the visual target is at a position corresponding to the focal length of the lens, and the focal length of the lens is 80 mm or more and 120 mm or less.

5. A portable eye refraction measuring device as described in claim 1 or 2, wherein when the first tube portion and the second tube portion are slid to their longest, the distance between the visual target and the lens is longer than the focal length of the lens.

6. A portable eye refractive power measuring device as described in claim 5, wherein the first tube portion has a first portion and a second portion that is slidable relative to the first portion and has the visual target provided thereon.

7. A portable eye refractive power measuring device as described in claim 1 or 2, further comprising a movement suppression member between the first tube portion and the second tube portion for suppressing movement of the first tube portion relative to the second tube portion.

8. A portable eye refractive power measuring device according to claim 7, wherein the movement suppressing member is provided extending in the longitudinal direction.

9. A portable eye refractive power measuring device according to claim 1 or 2, wherein the first tube portion and the second tube portion are polygonal prisms.

10. A portable eye refraction measuring device as described in claim 1 or 2, wherein the visual target is a pattern consisting of multiple black lines and multiple white lines arranged alternately, the multiple black lines having two or more different widths, and the multiple white lines having two or more different widths.

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