JP2006149871A - Ophthalmologic measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ophthalmologic measuring apparatus which is advantageous in terms of cost and can measure an optical characteristic such as the wave front aberration of an examined eye, etc. with high resolution. <P>SOLUTION: The apparatus includes: a projection optical system for projecting a spot shape light flux from a measurement light source to the eyeground of the examined eye; and a light receiving optical system which receives the light flux reflected from the eyeground and projecting the examined eye, has a mask pattern arranged at a substantially conjugated position with the pupil of the examined eye and has a two-dimensional imaging device arranged at the Talbot image of the mask pattern. The mask pattern has the orthogonal grid shape mask of a pitch which is formed so as to match with arrayal in the unit pixel size of the two-dimensional imaging device. The optical characteristic of the examined eye is measured based on a moire pattern which is generated by the Talbot image of the orthogonal grid shape mask and the pixel array of the two-dimensional imaging device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ophthalmologic measurement apparatus that measures optical characteristics of an eye to be examined.

A spot-like light beam is projected onto the fundus of the eye to be examined, and the light beam emitted from the eye as a secondary light source is extracted from a plurality of parts in the pupil, and the wavefront aberration distribution of the eye to be examined is obtained from information detected by a two-dimensional image sensor or the like. As an ophthalmologic apparatus for measuring the optical characteristics of an optical device, one using a so-called Shack-Hartmann wavefront sensor (for example, see Patent Document 1) and one using a moire pattern generated by two grating masks (diffraction gratings) (for example, a patent) Document 2) is known.
Japanese Patent Laid-Open No. 10-305013 Special table 2003-526404 gazette

The Shack-Hartmann wavefront sensor method disclosed in Patent Document 1 is configured to receive fundus reflection light with a two-dimensional imaging device through a microlens array, and thus the resolution in the pupil cannot be increased beyond a certain level. On the other hand, according to the method of analyzing the moire pattern, high-resolution measurement is possible. In Patent Document 2, a moire pattern generated by two lattice masks is projected on a screen and imaged by a two-dimensional image sensor via an imaging lens. However, further improvement is desired in the method using the moire pattern.
An object of the present invention is to provide an ophthalmic measurement apparatus that can measure optical characteristics such as wavefront aberration of an eye to be examined with high resolution and is advantageous in terms of cost.

In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) A projection optical system that projects a spot-like light beam from a measurement light source onto the fundus of the eye to be examined, and a light-receiving optical system that receives a light beam that is reflected from the fundus and exits the eye to be examined. And a light receiving optical system having a two-dimensional image sensor arranged at a Talbot image position of the mask pattern, and the mask pattern is arranged in a unit pixel size array of the two-dimensional image sensor. It has an orthogonal lattice mask with a pitch formed in combination, and measures optical characteristics of an eye to be inspected based on a Talbot image of the orthogonal lattice mask and a moire pattern generated by the pixel arrangement of the two-dimensional image sensor. To do. In this apparatus, each width of the transmissive part and the light-shielding part of the orthogonal grid mask is the same width as the unit pixel of the two-dimensional image sensor.
(2) In the ophthalmologic measurement apparatus according to (1), a moving means is provided for moving the mask pattern and the two-dimensional image sensor together with the measurement light source in the optical axis direction according to the spherical refraction error of the eye to be examined. To do.

  According to the present invention, optical characteristics such as wavefront aberration of the eye to be examined can be measured with high resolution, and the optical configuration is simplified, which is advantageous in terms of cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a measurement optical system and a control system of an ophthalmologic measurement apparatus. The optical system of the ophthalmic measurement apparatus includes an alignment optical system that projects an alignment index onto the eye to be examined and detects the index image in order to align the measurement optical system with respect to the eye to be examined, an anterior ocular segment observation optical system, A fixation target optical system for fixing the eye to be inspected and relaxing the adjustment of the crystalline lens is disposed.

  In FIG. 1, a measurement optical system 10 includes a projection optical system 10a that projects a spot-like light beam on the fundus and a light receiving optical system 10b that receives reflected light from the fundus. The projection optical system 10a includes a measurement light source 11 such as an LD or SLD that emits infrared light, a relay lens 12, a half mirror 13, and an objective lens 14, which are arranged in this order toward the eye to be examined. The light receiving optical system 10a is a two-dimensional image pickup device such as an objective lens 14, a half mirror 13, a relay lens 15, a mirror 16, a light receiving system diaphragm 17, a collate lens 18, an orthogonal lattice mask 19, and a CCD from the front of the eye to be examined. They are arranged in the order of 20. The objective lens 14 and the half mirror 13 of the projection optical system 10a are shared by the projection optical system 10b. The half mirror 13 transmits the measurement light beam from the light source 11 and reflects the reflected light from the fundus. The half mirror 13 may be a perforated mirror.

  In the orthogonal grating mask 19 which is a diffraction grating, a light-shielding portion having a light transmittance of approximately 0% and a light-transmitting portion having a transmittance of approximately 100% are formed in stripes in both horizontal and vertical directions. The mask 19 is disposed at a position optically conjugate with the pupil of the eye to be examined via the objective lens 14 to the relay lens 18. Further, the light receiving surface of the two-dimensional image sensor 20 is placed in the vicinity of the position where the Talbot image of the mask 19 is generated. Assuming that the distance between the mask 19 and the two-dimensional imaging device 20 is D, the position where the Talbot image is generated is shown below.

D = m · 2d ² / λ
d is a lattice constant (length of one cycle of ON / OFF) of the orthogonal lattice mask 19, λ is the wavelength of the measurement light source 11, and m is an integer.

  Here, the pitch of the lattice stripes of the orthogonal lattice mask 19 is formed in accordance with the unit pixel size of the two-dimensional image sensor 20 as shown in FIG. FIG. 2A is a diagram illustrating pixels arranged in the two-dimensional image sensor 20, and 20a represents a unit pixel. The size of the unit pixel 20a is W × W, for example, W = 7 μm. FIG. 2B is a diagram showing orthogonal lattice fringes of the orthogonal lattice mask 19, and 19a represents the lattice fringes. Each width of ON (transmission part) and OFF (light-shielding part) of the horizontal and vertical lattice stripes 19 a is the same width W as the unit pixel of the two-dimensional image sensor 20. If W = 7 μm, measurement can be performed with 71 lattice stripes per mm. Further, the orthogonal lattice mask 19 is arranged with a slight angular deviation θ around the optical axis with respect to the two-dimensional imaging device 20. The angle deviation θ is determined so that appropriate moire fringes can be formed in relation to the pitch of the lattice fringes of the orthogonal lattice mask 19.

In this apparatus, the measurement light source 11, the light receiving system diaphragm 17, the collate lens 18, the orthogonal lattice mask 19, and the two-dimensional imaging device 20 are moved as a unit 21 by the moving mechanism 22 in the optical axis direction. It has a configuration. By moving the measurement light source 11, the image sensor 20 and the like in the optical axis direction, the spherical refraction error of the eye to be examined is corrected, and the eye fundus to be examined, the measurement light source 11, and the light receiving diaphragm 17 are kept optically conjugate. This amount of movement is detected by a detector 23 such as a potentiometer. The moving mechanism 22, the detector 23, and the image sensor 20 are connected to the control unit 30.
Note that the orthogonal lattice mask 19 is optically conjugate with the eye pupil to be examined at a constant magnification by the objective lens 14, the relay lens 15, and the collimating lens 18 regardless of the movement position in the optical axis direction. ing.

  In the above configuration, the luminous flux emitted from the measurement light source 11 is projected as a spot-like luminous flux on the fundus of the eye to be examined by the relay lens 12 and the objective lens 14 to form a point light source image on the fundus. The point light source image projected on the fundus of the subject's eye is reflected and scattered, exits the subject's eye, is collected by the objective lens 14, and passes through the half mirror 13, relay lens 15, and mirror 16 to the position of the light receiving aperture 17. After being condensed, the collimator lens 18 makes a parallel light beam, and the light beam that has passed through the orthogonal lattice mask 19 is received by the image sensor 20.

  The moire pattern generated by the light flux that has passed through the orthogonal grid mask 19 and the unit element arrangement of the image sensor 20 is that the Talbot image of the orthogonal grid mask 19 formed in the vicinity of the image sensor 20 is disturbed by the aberration of the eye to be examined. Changes to reflect. Therefore, if the moiré pattern generated by the reflected light from the eye to be examined is analyzed with respect to the moiré pattern formed when non-aberration light (parallel light) passes, the wavefront aberration distribution and refractive power distribution of the eye to be examined are measured. It becomes possible.

  The control unit 30 has a program for obtaining the output image signal of the image sensor 20 and analyzing the wavefront aberration and the like of the eye to be examined, and also serves as means for analyzing the optical characteristics of the eye. As described above, the projected image of the orthogonal grid mask 19 on the image sensor 20 reflects the wavefront aberration of the eye to be examined. Moire fringes are generated by the overlap between the projected image and the unit element array of the image sensor 20. The control unit 30 obtains the inclination of the wavefront by detecting the local inclination of the moire fringes obtained by the image sensor 20. For the analysis of the inclination of the wavefront, a well-known mathematical technique as described in JP-T-2003-526404 can be used. The slope of the analyzed wavefront is quantified by applying the well-known Zernike polynomial expansion. The spherical refraction error and the astigmatic refraction error are expressed by a polynomial order of the second order or less, and the higher order aberration component is obtained by the polynomial order of the third order or more. Analysis results of optical characteristics such as wavefront aberration distribution and refractive power distribution are displayed on the monitor 31 connected to the control unit 30 in the form of a map or the like.

  When measuring the wavefront aberration distribution and the refractive power distribution, the unit 21 in which the measurement light source 11 and the light receiving system diaphragm 17 to the image sensor 20 are integrated is used to correct the spherical refraction error obtained by the preliminary measurement. Move in the axial direction. The movement amount is obtained by converting the movement position detected by the detector 23 into a spherical refraction error, and analyzing the wavefront aberration distribution and the refractive power distribution based on the spherical refraction error. Thus, by moving the unit 21 so as to correct the spherical refraction error of the eye to be inspected, the resolution at the time of analyzing moire fringes is not reduced, and the size of the light receiving surfaces of the orthogonal grid mask 19 and the image sensor 20 is reduced. It is possible to cope with measurement of a large refraction error without increasing the value.

  The resolution of the optical characteristics of the eye depends on the width of the unit element of the two-dimensional image sensor 20 and the orthogonal lattice mask 19. Since it is possible to use a finer lens than the microlens array used in the Shack-Hartmann method, it is possible to measure the optical characteristics of the eye with high resolution. In addition, since a configuration for generating a moire pattern is possible with one orthogonal lattice mask 19 and the two-dimensional imaging device 20, the constituent members can be simplified compared to the conventional case, which is advantageous in terms of cost.

It is a schematic block diagram of the measurement optical system and control system of an ophthalmologic measurement apparatus. It is a figure explaining the orthogonal lattice mask formed according to the unit pixel size of a two-dimensional image sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Measurement optical system 10a Projection optical system 10b Light reception optical system 11 Measurement light source 19 Orthogonal lattice mask 20 Two-dimensional image sensor 22 Moving mechanism 30 Control unit

Claims (2)

A projection optical system that projects a spot-like light beam from the measurement light source onto the fundus of the eye to be examined, and a light-receiving optical system that receives the light beam that is reflected off the fundus and exits the eye to be examined. And a light receiving optical system having a two-dimensional image sensor arranged at the Talbot image position of the mask pattern, the mask pattern being formed in accordance with the unit pixel size arrangement of the two-dimensional image sensor An ophthalmic measurement comprising: measuring an optical characteristic of an eye to be inspected based on a Talbot image of the orthogonal lattice mask and a moire pattern generated by a pixel arrangement of the two-dimensional image sensor. apparatus 2. The ophthalmologic measurement apparatus according to claim 1, further comprising moving means for moving the mask pattern and the two-dimensional image sensor together with the measurement light source in an optical axis direction according to a spherical refraction error of the eye to be examined. apparatus.