JP2817794B2 - Eye refractive power measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eye refractive power measuring device, and more particularly to an eye refractive power measuring device useful for children to infants.

[Prior Art] Conventionally, as an eye refractive power measuring device, there are a so-called subjective ophthalmoscope for measuring eye refractive power based on a response of a subject, a so-called auto-refractometer for objectively measuring an eye to be examined, and the like. Devices are known.

However, when measuring infants with this kind of device, it is not possible to measure with a subjective ophthalmoscope because of the lack of cooperation of infants, and the position of the eye to be examined must be fixed with a general auto-refractometer. However, in the case of infants, it is difficult to fix the position of the eye to be examined, and the measurement is extremely difficult.

In order to eliminate these drawbacks, a so-called photorefraction method is used in which the fundus of the subject's eye is illuminated with strobe light, the state of the luminous flux at the pupil of the subject's eye is photographed with a camera, and the eye refractive power of the subject's eye is measured from the result. Measurement methods have been proposed.

In this photorefraction method measurement, it is possible to sufficiently measure even if the optical axis of the eye to be examined is slightly deviated, and it is useful for measuring the refractive power of infants who have difficulty fixing the eye to be examined. It is supposed to be.

[Problems to be Solved by the Invention] In a conventional apparatus of this kind, a strobe light source illuminates an optical axis of a camera from a diagonal direction, and a pupil image at that time is simply taken. There is a problem that there is a diopter value that cannot be measured depending on the position, and that the measurable range is narrow.

In order to solve such a problem, the applicant of the present application
In Japanese Patent Application No. 63-238505, an image of a light source is projected on the fundus of the eye to be inspected, the light beam reflected from the fundus from the light source is blocked by an edge-shaped light blocking member, and the blocked light beam is received by a light receiving element. An eye-refractive-power measuring device for measuring the eye-refractive power based on the light quantity distribution state of the eye was proposed.

In the case of the photorefractive method, it is necessary to focus the image, but in the conventional method, the focus of the lens is set at a certain fixed position, and the subject goes within the focus range. The eye refractive power was measured after focusing by moving the lens. Therefore, there is a problem in that preparations before the start of the measurement are required, rapid measurement cannot be performed, and a focus error is large, so that an accurate measured value cannot be obtained. It is also possible to perform focusing by moving the entire apparatus, but in that case, a moving mechanism for moving the entire apparatus is required, and there is a problem that the entire apparatus becomes large.

Therefore, the present invention is based on the eye refractive power measuring device according to the earlier application, and provides an eye refractive power measuring device that can quickly focus by moving only the objective lens and that can perform highly accurate measurement with less error. It is assumed that.

Means for Solving the Problems According to the present invention, a projection system for projecting a light source image onto the fundus of the eye to be examined and a light receiving element arranged at a position substantially conjugate with the pupil of the eye to be examined receive light beams from the fundus. A light-receiving system, and an edge-shaped light-blocking member disposed in an optical path of the light-receiving system to block a part of the received light beam, and a pupil image is formed on the light-receiving element by moving an objective lens constituting the light-receiving system. And the eye refractive power of the eye to be examined can be measured based on the amount of movement of the objective lens and the amount of light distribution of the light beam projected on the light receiving element. Things.

[Operation] The state in which the light-shielding member blocks light is different depending on the eye refractive power of the eye to be examined. The light-shielding state and the eye refractive power correspond to each other, and the state of the light beam projected on the light-receiving element, that is, the light amount distribution and the relative positional relationship between the subject's eye, the light-shielding member, and the light-receiving system, that is, the eye movement amount based on the movement amount of the lens. Refractive power can be measured.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

First, a description will be given of the eye refractive power measuring device previously applied in FIGS. 2 (A), 2 (B) and 2 (C) to FIG.

2 (A), 2 (B) and 2 (C), reference numeral 1 denotes a projection system for projecting a light source image onto the fundus 7 of the eye 3 to be inspected, and 2 a light beam 10 reflected by the fundus 7. The projection system 1 and the light receiving system 2 are arranged to face the subject's eye 3.

The projection system 1 includes a light source 4 and a half mirror 5 for reflecting a light beam 11 from the light source 4 toward the subject's eye 3. The projection system 1 transmits the light beam 11 from the light source 4 onto a fundus 7 through a pupil 6. To form an image of the light source 4 on the
The distance between the light source 4 and the eye 3 is set so that the image of the light source 4 is focused on the fundus 7 when the eye refractive power of the eye 3 is a reference diopter value (reference refractive power).

The light receiving system 2 includes an objective lens 8 and a light receiving element 9, and a light beam 10 from the fundus 7 passes through the half mirror 5 and is guided onto the light receiving element 9.

The light receiving element 9 includes an area CCD, an image pickup tube, or a combination thereof.
The light receiving surface 9a of the light receiving element 9 is arranged at a position conjugate with the pupil 6 of the subject's eye 3 with respect to the objective lens 8.

In the optical path of the light receiving system 2, an edge-shaped light shielding member 12 for shielding one side of the light flux 10 with the optical axis O of the objective lens 8 as a boundary is disposed at a position conjugate with the light source 4 with respect to the half mirror 5.

As shown in FIG. 2 (A), when the diopter value of the eye 3 to be examined is a negative diopter value compared to the reference diopter value, the image of the light source 4 is formed in front of the fundus 7, and this light beam causes Considering the light beam 10 reflected at one point on the optical axis among the illuminated fundus 7, the light beam 10 is condensed in front of the light shielding member 12, that is, on the side of the eye 3 to be examined, and is received by the objective lens 8. The upper half (hatched portion) of the light beam projected onto the element 9 is shielded.

On the other hand, as shown in FIG. 2 (B), when the diopter value of the eye to be inspected is the reference diopter value, the light beam 10 is condensed on the light shielding member 12, and the light beam 10 is Not blocked.

As shown in FIG. 2C, when the diopter value of the eye 3 is more positive than the reference diopter value, the image of the light source 4 is projected so as to form an image behind the fundus 7, and as described above. Similarly, the light beam 10 reflected by the fundus 7 is collected behind the light blocking member 12, that is, on the light receiving element 9 side, and the light beam 10 projected on the light receiving element 9 is a portion opposite to that of FIG. The light flux (the upper half in the figure) is shielded.

Thus, the light flux projected on the light receiving surface 9a changes its light quantity distribution state with respect to the reference diopter value depending on the magnitude of the diopter value of the eye to be inspected 3 and the sign thereof, and the diopter value is determined based on this light quantity distribution state.

The light receiving element 9 is for detecting the light amount distribution of the light beam formed on the light receiving surface 9a, and the arithmetic unit 13 is configured to detect the light amount distribution of the light beam formed on the light receiving surface 9a based on the signal from the light receiving element 9. The light amount distribution is detected, it is determined whether the eye refractive power of the eye to be examined is positive or negative with respect to a reference diopter value, and the absolute value is calculated.

In the above embodiment, a half mirror is used as a light beam separating means. However, it is a matter of course that various light beam separating means such as a beam splitter and a polarizing prism are used.

In the following, the distribution of the amount of light of the light beam formed on the light receiving surface 9a will be described with reference to FIGS.

In order to simplify the explanation in FIGS. 3A to 3E, the optical axis of the light source 4 and the optical axis of the light receiving system are matched, and the light shielding member 12 and the objective lens 8 are matched. I have. For this reason, the light source 4 and the objective lens 8 are shown superimposed at the same position, and the light shielding member 12 is omitted.

Figure 3 (A) ~ (E) is the light receiving surface by all reflected light beam objective lens 8 from the shows the case where the refractive power D of the eye is negative with respect to the reference power D _0, the following description fundus It shall be projected on 9a.

Assuming that the distance between the light source 4 and the pupil 6 of the subject's eye is set to 1 and the refractive power of the subject's eye at which the image of this light source is focused on the fundus is the reference refractive power D ₀ It is.

FIG. 3 (A) shows a case where the refractive power of the subject's eye is D (<D ₀ ) from one point S ₀ on the axis of the slit-shaped light source 4 having a length L in a direction perpendicular to the optical axis. Indicates the projected light flux,
The image of the point S ₀ is once formed on S ₀ ′,
Projected as a blurred image. Region 7a where D ₀ -D is projected in accordance with increase becomes wider.

FIG. 3B shows the state of the light beam reflected from the light receiving system 2 and the fundus 7 of the eye to be examined.

As shown in FIG. 3 (B), considering the light flux from a point I- _n at the end of the projection area on the fundus 7 of the eye to be examined, an image I- _n 'of this point is considered.
Is imaged at a position 1 'away from the pupil of the eye to be examined, and this light beam is projected via the objective lens 8 onto a light receiving element 9 arranged at a position conjugate with the pupil 6 of the eye to be examined. The relational expression between l 'and the refractive power D of the eye to be examined is as follows.

On the other hand, assuming that the pupil diameter of the subject's eye is u, the spread width Δ of the light flux emitted from one point on the fundus is as shown in FIG. From the equations (1) and (2). Thus, as the difference between the refractive power D of the eye 3 to be examined and the reference refractive power D ₀ increases, the spread on the light shielding member 12 increases.

Next, the spread of the light beam on the light receiving element 9 will be described. The light receiving element 9 is always irrespective of the refractive power of the eye 3 to be inspected.
Assuming that the objective lens 8 is arranged conjugate with the pupil of the eye to be inspected, the diameter of the pupil 6 of the eye to be inspected is u, and the magnification of the objective lens 8 is β, the light receiving element 9 has an area of the diameter of βu (the refractive power of the eye to be inspected). (Unaffected).

Further, after forming an even as well the light flux from the eye pupil 6 'image I _n to the position of' l from the phase _-n symmetrical point I _n with respect to the optical axis, the same area on the light receiving element 9 projected onto βu. Light source 4
As a point light source, when that there is no light blocking member 12, the points I _-n from these fundus _{7, ... I 0, ...... I} n, the integral of the light beam from determining the light intensity distribution on the light receiving element 9 Things.

Here, in order to consider the light amount distribution on the light receiving element 9, the light flux incident on the end position P _-n of the light beam projection position on the light receiving element 9, that is, the coordinate position -βu / 2 centered on the optical axis. In consideration of the above, the light beam incident on this position is limited to the light beam in the range of oblique line A in FIG. 3 (C).
Similarly, considering the light flux incident on the position _Pn symmetrical to the P- _n position with respect to the optical axis, the light flux is limited to the light flux in the range of the hatched line A '. Then, from the eye pupil 6 to be examined
Distance the light beam incident on the position of P _-n on the light receiving element 9 and to place the edge-like light blocking member 12 for blocking one of the light beam A 'of the optical axis at the position of (the light source 4 and conjugate position) the light blocking member 12 not blocked by the light beam toward the upper position from the position of the P _-n is gradually shading, half of the light beam is blocked by the center P ₀ position, all of the light flux becomes a position of P _n is blocked That is the thing. Therefore, the edge-shaped light shielding member 12
As a result, the light becomes darker as it goes upward on the light receiving element 19, and the light quantity distribution has a constant slope where the light quantity becomes 0 at the point _Pn .

In FIGS. 3A to 3C described above, only the light flux emitted from one point on the optical axis of the light source 4 is shown. However, one point S _-n at the end of the light source 4 (where the size of the light source is L) Considering the luminous flux from the point (-L / 2 coordinate position), the result is as shown in FIG. 3 (D). Light beam from the point S _-n are projected from I _-n point on the fundus 7 shown in FIG. 3 (D) in the region of I _n points, this I _-n
Point, the reflected light from I _n points, after forming an image of, I _n '' I _n at a distance of 'l from the eye pupil 6 in the same manner as described above, the diameter of βu on the light receiving element 9 Is projected on the area of.
Here, of the luminous flux emitted from the point S- _n at the end of the light source 4,
The light beam incident on the end position P- _n of the light beam projection on the light receiving element 9 is a light beam in a hatched area B in FIG. 3 (D).

Further, the S consider the light beam from one point S _n of the point symmetrical with the light source 4 _-n, of which Figure 3 Given the light beams incident on the point P _-n on the light receiving element 9 C of (E) It becomes a light flux in the inclined area. As described above, when the light source 4 is considered to have a certain size, the amount of light at one point on the light receiving element 9 must be considered as the sum of the light flux from each point of the light source 4.

FIG. 4 (A) shows the respective light beams incident on the position of P- _n on the light receiving element 9 superimposed on the basis of this concept, and shows the light beams emitted from the position of _Sn on the light source. Of which P _-n
Is incident on the area B (FIG. 3 (D)).
), The light flux also moves upward as the position on the light source goes upward, and at the light source position S ₀ on the axis, it becomes a light flux in the area A (see FIG. 3 (C)), and the light beam C region at the position of S _n (see FIG. 3 (E)). Therefore, the light quantity at the point P- _n on the light receiving element 9 can be considered as the sum of these light fluxes.

Here, a light shielding member is provided at a position of a distance 1 from the pupil 6 of the eye to be examined.
FIG. 4B is a schematic diagram showing the amount of P- _n light at a point on the light receiving element 9 when 12 is arranged. FIG. 4 (B) shows how the light beam is blocked by the light blocking member 12 as the position on the light source changes. The horizontal axis in FIG. 4 (B) shows the coordinate position on the light source, and the vertical axis shows the light amount. Considering the light flux from each point on the light source, -L / 2 (L is the light source The light flux from the point () to the point 0 is not blocked by the light blocking member, but is gradually blocked after passing the coordinate point 0, and all the light flux is blocked at the position of Δ (the spread of the light flux). That is the thing. FIG. 4B shows the contribution of the light amount from each point on the light source, where k is the light amount from each point on the light source when the light is not blocked.
And the area of the hatched portion corresponds to the light amount at the point P- _n on the light receiving element. This area value T is as follows.

Similarly, other points on the light receiving element will be considered. FIG. 5 (A) shows the light beam incident on the center point P ₀ on the light receiving element in the same manner as FIG. 4 (A), and P out of the light beam from the point S _−n on the light source. _The light flux incident on the point _{0 is} a shaded area of B ₀ , the light flux from the point S ₀ on the light source is the shaded area of A ₀ , and the light flux from the point S _n on the light source is the light flux of the shaded area C _0. is intended, the amount of light incident on the center of the light receiving element 9 will correspond to the area T ₀ of the hatched region of FIG. 5 (B). That is, considering the light flux incident on the center point of the light receiving element from each point of the light source, -Δ /
The luminous flux is not blocked until the position of 2, and after passing the -Δ / 2 position, the luminous flux is gradually blocked, and all the luminous flux is blocked at the position of Δ / 2. The following values are calculated.

Similarly, FIGS. 6A and 6B show the state of the light beam incident on the point _Pn on the light receiving element and the light amount value at this point. Figure 6 (A), the light beam incident on the point of the inner P _n of the light beam from the point S _-n on the light source B hatched "shaded area of, A is the center point S ₀ on the light source" region, the light beam from a point P _-n on the light source shown as light flux hatched area in C ". in this case, as shown in FIG. 6 (B), P _n of the light receiving elements from each point light source Considering the luminous flux incident on the point
From the position of -L / 2 on the light source to the position of -Δ, the light beam is not blocked, and after passing the -Δ position, the light beam is gradually blocked, and all the light beams are blocked at the position of 0, When this area value is calculated, the following value is obtained.

As can be seen from the results of Equations (4), (5), and (6), the light amount value on the light receiving element 9 gradually decreases as going from lower to upper. The light intensity distribution on the element changes linearly as shown in FIG.

In the above description, the description has been made on the assumption that the spread width Δ on the light blocking member 12 when considering the light flux emitted from one point of the fundus is smaller than 1/2 of the size L of the light source. It is.

However In other words, when the deviation ΔD of the diopter value of the subject's eye with respect to the reference diopter value D ₀ is equal to or larger than a predetermined amount,
A linear change as shown in the figure is not shown. This will be described with reference to FIGS. 4 to 6. As aforementioned In the case of FIG. 4, FIGS. 4 (B), 5 (B), and 6 (B) are as shown in FIGS. 11, 12, and 13, respectively. It does not show a linear change as shown in FIG.

Next, when the refractive power of the subject's eye shown in FIG. 2 (B) is the reference value, and when the refractive power of the subject's eye shown in FIG. 2 (C) is more positive than the reference value, the same as described above. The light amount distribution on the light receiving element 9 can be considered. In this case, when the refractive power of the eye to be examined is a reference value, as shown in FIG. The distribution state is opposite to that shown in FIG.

The diopter value (refractive power) is the slope of the light amount distribution described above.
And the direction of the slope represents the sign of the diopter value. This will be described below with reference to FIG.

The slope of the light distribution Is defined as The spread Δ of the light beam, that is, the amount of blur Δ, is given by the above equation (4). Therefore, from equation (7) Thus, equation (9) gives the deviation ΔD of the diopter value of the subject's eye with respect to the reference diopter value D ₀ . Are proportional. Therefore, the image processing unit
From the light intensity distribution at 15 , It is possible to obtain the diopter value of the eye to be examined.

 Next, an embodiment of the present invention will be described with reference to FIG.

1 that are the same as those shown in FIG. 2 are denoted by the same reference numerals.

The objective lens 8 is supported so as to be movable in the optical axis direction, and is driven by a pulse motor 14 or the like via a drive mechanism 13 such as a rack and pinion or a nut and screw. .

The light receiving element 9 is connected to an image processing unit 15 for processing and calculating a signal from the light receiving element 9, and a main control unit 16 is connected to the image processing unit 15, and the main control unit 16 is connected to the image processing unit 15. Drive control unit
17 is connected. The pulse motor 14 driven by the drive control unit 17 includes a rotation detector 18 such as an encoder.
The detection result from the rotation detector 18 is fed back to the drive control unit 17. A display 19 is connected to the image processing unit 15 so that the calculation result of the image processing unit 15 is displayed.

As described above, in the present invention, an image of the pupil of the eye to be inspected is formed on the light receiving element 9. The adjustment for forming the image is performed as follows.

The defocus state of the image on the light receiving element 9 is determined by the image processing unit 15.
, And inputs the result to the main control unit 16. The main control unit 16 issues a drive command signal to the drive control unit 17 based on a signal from the image processing unit 15. The drive control unit 17 drives the pulse motor 14 according to the drive command signal to drive the objective lens 8
The amount of movement of the pulse motor 14 (the amount of movement of the objective lens 8) for moving the object in the x or -x direction is detected by the rotation detector 18 and fed back to the drive control unit 17, so that the amount of movement of the pulse motor 14 A match with the signal is made.

As described above, when the objective lens 8 is moved in accordance with the position of the pupil 6, the relative positions of the pupil 6, the light shielding member 12, the objective lens 8, and the light receiving element 9 are different from the above-described reference relative positions. Become.

However, as described above, the deviation ΔD of the diopter value is related to the distance 1 between the light source 4, that is, the light blocking member 12 and the pupil 6 of the subject's eye, and the magnification β, so that the equation (9) must be corrected.

 Hereinafter, this correction will be described.

When the objective lens 8 is arranged at the reference position x = 0, the light shielding member
It is assumed that an image of the pupil 6 arranged at a reference position separated by 1 from 12 is formed on the light receiving surface 9a at a magnification β. In this case, the distance m ₁ between the objective lens 8 having the focal length f of the objective lens 8 and the light receiving surface 9a is J (1 + β).

Here, assuming that the subject's eye 3 is displaced from the proper position and the objective lens 8 is moved by Δx to form an image of the pupil on the light receiving surface 9a, the distance between the light receiving surface 9a and the objective lens 8 at that time m ₂ is represented by the following equation.

m ₂ = m ₁ −Δx = J (1 + β) −Δx (10) Further, if the magnification after moving the lens is β ′, this distance m ₂ is J (1 + β ′). Is J (1 + β) −Δx = J (1 + β ′) (11) From the equation (11), the magnification β 'after moving the objective lens 8 by Δx is Becomes

Next, the distance (distance from the light source 4) between the eye to be examined and the light shielding member 12 after the objective lens 8 is moved by Δx to form an image of the pupil 6 on the light receiving surface 9a will be considered.

The amount of change Δl in the distance between the light-shielding member 12 and the subject's eye 3 caused by the movement of the objective lens 8, the amount of change Δm in the distance between the light-shielding member 12 and the objective lens 8, and the amount of change in the distance between the subject's eye 3 and the objective 8 The following relational expression holds between Δn.

Δn = Δl + Δm (13) Here, Δm does not deviate from the movement amount of the lens, and Δm = Δx (14) In addition, the distance between the objective lens 8 and the subject's eye when the magnification is β is When the objective lens 8 is moved by Δx and the magnification becomes β ′, the distance is Where Δn is By substituting the equation (12), Becomes Therefore, from equations (13) to (15) Becomes Therefore, when the objective lens 8 is moved by Δx, the distance l _X between the subject's eye 3 and the light shielding member 12 is Therefore, the reference diopter value D _O accompanying the movement of the objective lens 8 becomes D _O 'below.

Thus, equation (9) is Becomes

Thus, the amount of movement Δ of the objective lens 8 when focusing is achieved
x is fed back from the rotation detector 18 to the main control unit 16 to calculate equations (17) and (18). Based on the result obtained in this calculation, a more accurate diopter value than equation (9 ') is obtained. The deviation can be determined.

The obtained diopter value deviation is converted into a diopter value of the subject's eye and displayed on the display 19.

[Effects of the Invention] As described above, according to the present invention, the subject does not need to move to an appropriate position for measurement, and focus adjustment can be easily performed by moving only the objective lens. And the operability of the measurement can be improved, and the focusing can be performed accurately, so that the measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a basic schematic diagram of the present invention, and FIGS. 2 (A) and 2 (B).
(C) is an explanatory view showing an outline of an eye refractive power measuring apparatus which is a basis of the present invention and showing a difference in a state of a light beam due to a difference in a diopter value of an eye to be examined, and FIGS. 3 (A), (B), and (C).
(D) and (E) are explanatory diagrams showing the state of the light beam reflected from the light receiving system and the fundus of the eye to be examined, FIGS. 4 (A), 5 (A), and 6
FIG. 4A is an explanatory view showing the state of reflected light flux at each point of the light source reaching the light receiving element, and FIGS. 4B, 5B, and 6B are shielded by a light blocking member. FIG. 7, FIG. 8, FIG. 9, and FIG. 9 are explanatory diagrams showing a light amount distribution state on a light receiving surface corresponding to a diopter value, and FIG. FIG. 11, FIG. 12, FIG. 13, and FIG. 13 show the case where the light flux is shielded by the light shielding member when the spread width Δ on the light shielding member is larger than half the size of the light source. FIG. 4 is an explanatory diagram showing a change in light amount of the light. 1 is a projection system, 2 is a light receiving system, 3 is an eye to be examined, 4 is a light source, 5 is a half mirror, 8 is an objective lens, 13 is a driving mechanism, 15 is an image processing unit, 16 is a main control unit, and 17 is drive control. Reference numeral 18 denotes a rotation detector.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Noriyuki Nagai 75-1, Hasunuma-cho, Itabashi-ku, Tokyo Inside Tokyo Optical Machinery Co., Ltd. (72) Inventor Yasuhisa Ishikura 75-1, Hasunuma-cho, Itabashi-ku, Tokyo Tokyo Optical Machinery Co., Ltd. (56) Reference Optics Vol. 18, No. 10, PP. 545-546 (58) Fields investigated (Int. Cl. ⁶ , DB name) A61B 3/103

Claims (1)

(57) [Claims] A light source system for projecting a light source image on a fundus of a subject's eye; a light receiving system for receiving a light beam from the fundus on a light receiving element disposed at a position substantially conjugate with a pupil of the subject's eye; An edge-shaped light-blocking member for blocking part of the received light beam disposed in the optical path, such that a pupil image is formed on the light-receiving element by moving an objective lens constituting the light-receiving system. An eye-refractive-power measuring apparatus, characterized in that the eye-refractive-power measuring device is configured to be able to measure the eye-refractive power of the eye to be inspected based on the amount of movement of the objective lens and the light amount distribution of the light beam projected on the light receiving element.