JP2006081841A - Image forming apparatus and wave front correcting optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of sufficiently correcting reflection light including astigmatism from an object such as the fundus oculi even if a wave front aberration correction element with restriction on the correctable aberration is used. <P>SOLUTION: The image forming apparatus comprises wave front aberration measuring parts 5 and 81 for receiving the luminous flux from the object 60 and measuring the aberration of the wave front, an image forming optical system 3 for receiving the luminous flux from the object 60 via at least two wave front aberration correcting optical elements 71 and 72 and forming an image of the object 60, and a control part for controlling the quantity of correction of the aberration of the wave front aberration correcting optical elements based on the aberration of the wave front measured by the wave front aberration measuring parts 5 and 81. The image forming apparatus is characterized by the wave front aberration correcting optical elements at least one of which corrects the wave front of the astigmatism component and the other of which corrects the wave front of components other than the astigmatism component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical characteristic measuring apparatus that measures the refractive power and corneal wavefront aberration of the eye, and an image forming apparatus suitable for use in a fundus camera that records a fundus image of the eye to be examined. The present invention relates to an image forming apparatus that is suitable for use in an eye characteristic measuring apparatus that measures a clear fundus image, accurate refractive power, and corneal wavefront aberration. The present invention also relates to a wavefront correcting optical apparatus suitable for use in a fundus camera that records a fundus image of an eye to be examined.

  In a fundus observation device such as a fundus camera, a fundus image is taken, and an ophthalmologist or an optometrist examines the state of the retina, fundus bleeding, and the like. By the way, the human eye optical system is composed of an eyeball composed of a cornea, a crystalline lens, a glass body, etc., but compared with a perfect optical system assumed in geometrical optics, the human eye optical system has There is distortion. In particular, in the field of ophthalmology, since the degree to which the subject's eye deviates from the normal eye is used as diagnostic information, a clear fundus image with little aberration is required. However, since the eye optical system constituting the object to be imaged is incomplete, there are cases where sufficient resolution cannot be obtained. Therefore, in order to correct the collapse of the wavefront in the eye optical system, for example, as shown in Patent Documents 1 and 2, a deformable mirror using a piezoelectric effect is used. However, when correcting reflected light including aberrations from the fundus, there is a case where the correction amount obtained from the displacement amount by a single deformable mirror may not be sufficient to obtain a clear fundus image. was there.

  The corneal wavefront aberration is expressed by a Zernike coefficient (Zernike) as shown in Patent Document 3, for example, and the Zernike coefficient is also converted into a diopter value. In the conventional fundus camera, the cylinder component (Zernike (2. ± 2) component) corresponding to the astigmatism of the wavefront aberration is corrected by the correcting cylinder lens inserted in the optical path. However, the refractive power interval of the cylinder lens is limited to a certain interval (for example, 3D (diopter) interval), and a clear fundus image in which aberrations are sufficiently corrected cannot be obtained with the constant refractive index. was there.

Japanese Patent Laid-Open No. 11-137522 [0031], FIG. US Pat. No. 6,042,223, column 3, lines 51-65, FIG. JP, 2002-209854, A [0039], [0090], FIG. 19, FIG.

  The present invention solves the above-described problems, and a first object is to provide reflected light including astigmatism from an object such as the fundus even when a wavefront aberration correction element that limits the aberration that can be corrected is used. An image forming apparatus capable of sufficiently correcting the above is provided. It is another object of the present invention to provide a wavefront correcting optical apparatus for use in an image forming apparatus, which is suitable for use in a fundus camera that records a fundus image of an eye to be examined.

  The image forming apparatus of the present invention that achieves the above object includes, as shown in FIG. 5, for example, a wavefront aberration measuring unit (5, 81) that receives a light beam from an object 60 and measures wavefront aberration, and an object. The light beam from 60 is received through at least two wavefront aberration correcting optical elements (71, 72), and measured by the image forming optical system 3 that forms an image of the object 60 and the wavefront aberration measuring unit (5, 81). An image forming apparatus including a control unit that controls an aberration correction amount of the wavefront aberration correction optical element based on the wavefront aberration, wherein at least one of the wavefront aberration correction optical elements performs wavefront correction of an astigmatism component, The other wavefront aberration correcting optical element is characterized by performing wavefront correction excluding astigmatism components.

  In the apparatus configured as described above, the wavefront aberration measuring unit (5, 81) receives the reflected light reflected from the fundus 61 and measures the wavefront aberration. The image forming optical system 3 receives and observes the light beam from the fundus 61 via at least two wavefront aberration correction optical elements. Here, based on the wavefront aberration measured by the control unit at the wavefront aberration measuring unit (5, 81), one wavefront aberration correcting optical element performs wavefront correction of the astigmatism component, and the other wavefront aberration correcting optical element is Since the wavefront correction excluding the astigmatism component is performed, fine aberration including the astigmatism component generated in the wavefront can be corrected.

  In the image forming apparatus of the present invention, preferably, the object 60 is a fundus 61 to be examined, and further includes an illumination optical system 2 that illuminates the fundus 61 of the eye to be examined, and the image forming optical system 3 has a fundus 61 to be examined. It is preferable that the image is formed.

  In the image forming apparatus of the present invention, preferably, the wavefront aberration correction optical element (71, 72) is formed of a deformable mirror, the first electrode provided on the deformable mirror side of the deformable mirror, and the first electrode Forming a pair of electrodes with a second electrode provided on the side facing the first electrode, and the shape of the wavefront aberration correcting optical element is variable by a voltage applied to the first electrode and the second electrode. It is comprised so that it may become.

  The wavefront correction optical apparatus of the present invention that achieves the above object includes, for example, as shown in FIG. 5, a light receiving optical system 3 that receives a light beam from the eye 60 or an illumination optical system 2 that irradiates the eye with the light beam. Control calculation for calculating the control amounts of the deformable mirrors (71, 72) arranged in the light path of the light beam of at least one optical system and the deformable mirrors (71, 72) required for correcting the aberration of the light beam wavefront In the wavefront correcting optical apparatus including the unit 8, for example, as shown in FIG. 3A, the deformable mirror that performs wavefront correction of the astigmatism component includes the first electrode provided on the deformable mirror side, A pair of electrodes with a second electrode provided on the side facing the first electrode is formed, and the shape of the wavefront aberration correcting optical element is variable by a voltage applied to the first electrode and the second electrode. And configured to be light And is configured to include a deformable mirror rotator for rotating freely rotate the deformable mirror around.

  In the wavefront correcting optical apparatus of the present invention, preferably, the deformable mirror that performs wavefront correction of the astigmatism component has a strip-like electrode shape, and compares the width of the center of each strip electrode with the vicinity of the edge. It is good to make it the structure which formed narrowly or formed each strip electrode with the equal width | variety.

  According to the image forming apparatus of the present invention having such a configuration, at least one of the wavefront aberration correcting optical elements performs wavefront correction of the astigmatism component, and the other wavefront aberration correcting optical elements are wavefronts excluding the astigmatism component. Since it is configured to perform correction, the use of a dedicated wavefront aberration correction optical element that compensates for the astigmatism component makes it possible to separate the function from the wavefront aberration correction optical element that performs wavefront correction excluding the astigmatism component, thus providing a clear image. Can be obtained.

  Further, according to the wavefront correcting optical apparatus of the present invention having such a configuration, a strip-shaped electrode shape can be used as a deformable mirror for performing wavefront correction of astigmatism components, and the configuration of the wavefront aberration correcting optical element is Compared with a wavefront correcting deformable mirror excluding the astigmatism component, the electrode distribution becomes simple.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[principle]
1A and 1B are configuration diagrams showing an example of an electrostatic deformable mirror, in which FIG. 1A is a plan view, FIG. 1B is a sectional view taken along line BB in FIG. Show. In the figure, the electrostatic deformable mirror 10 includes an electrode substrate 11, a silicon substrate 12, a membrane 13, a spacer 14, a reflective film 15, and an electrode 16. The membrane 13 is manufactured by a selective etching process on the silicon substrate 12 and has flexibility, for example, a thickness of about 4 μm. The reflective film 15 is formed by vapor-depositing a material having a high reflectance on the membrane 13, and for example, a metal film having a high reflectance such as aluminum is used. The spacer 14 is used to maintain the gap length between the membrane 13 and the electrode 16 at a predetermined value. For example, a highly rigid sphere is used. A predetermined number of electrodes 16 are formed on the electrode substrate 11. The electrodes 16a, 16b, 16c, 16d, and 16e are individually voltage-driven by the voltage control circuit 17.

  FIG. 2 is a plan view illustrating an example of an electrode arrangement of a deformable mirror that performs wavefront correction excluding astigmatism components. The electrode of the deformable mirror is, for example, a hexagonal honeycomb. 1-No. For example, an electrostatic voltage is applied so that deformation corresponding to each electrode occurs.

  3A and 3B are explanatory views showing the structure of a deformable mirror suitable for performing wavefront correction of an astigmatism (cylinder) component. FIG. 3A is a plan view, FIG. 3B is a sectional view, and FIG. (D) is an explanatory view of an electrode shape, and (E) is an explanatory view of another electrode shape. The deformable mirror 10 for correcting the wavefront of the astigmatism component is obtained by etching a rectangular main body portion 10a in the longitudinal direction by a thin film portion corresponding to the membrane portion 10c and a gap between the thin film portion and the frame body 10b. The portion 10d is provided at the top and bottom, and the membrane portion is configured to be deformable in the longitudinal direction. A mirror surface is formed on the surface of the membrane portion 10c. Here, the frame 10a and the membrane portion 10c form a first electrode made of silicon. The membrane portion 10c is fixed at both ends, and the central portion is a tensile portion.

  The cross-sectional structure of the deformable mirror 10 is shown in FIG. 3B. The frame 10a is supported on the electrode substrate 10e via the spacer 10f, and the membrane portion 10c is formed on the electrode substrate. The 2nd electrode is formed in the position facing. When a predetermined voltage is applied to the membrane portion 10c corresponding to the first electrode and the second electrode formed on the electrode substrate, the deformable mirror is deformed by the electrostatic force generated between the electrodes. As shown in FIG. 3C, when a voltage is applied, the deformable mirror 10 has a concave shape with a radius of curvature R.

  FIG. 3D illustrates an example of the electrode shape of the second electrode in the deformable mirror that performs wavefront correction of the astigmatism component. In this case, an electrostatic force is applied to the entire membrane portion 10c. FIG. 3E is a diagram for explaining another example of the strip-shaped electrode shape in the deformable mirror that performs wavefront correction of the astigmatism component. The width of each strip electrode may be uniform between the center and the periphery, or the width of the periphery may be wider than the center.

  4A and 4B are diagrams illustrating an example of a rotating unit that rotates the wavefront correcting variable shape mirror of the cylinder component. The deformable mirror is controlled by a stepping motor so that the axial angle direction acting as a cylinder lens is variably controlled. Here, the rotation angle of the deformable mirror is set according to the component to be corrected. For example, when the Zernike coefficient Z (2, 2) is corrected, the Zernike coefficient Z (2, -2) is corrected in the direction (0 degree direction) of FIG. 4 (D) direction (45 degree direction) is rotated.

  Here, a fundus oculi observation device will be described as an example of an image forming apparatus. FIG. 5 is a configuration block diagram for explaining an example of the entire fundus oculi observation device according to the present invention. In the figure, the fundus oculi observation device includes a fundus illumination system 2, a fundus oculi observation system 3, a point image projection optical system 4, a point image light receiving optical system 5, a voltage change template DB 6, an adaptive optics system 7, a computer 8, and an operation control unit 9. Is provided. Here, the point image projection optical system 4 and the point image light receiving optical system 5 constitute a wavefront measurement system, and the wavefront measurement system and the computer 8 constitute a wavefront correction system. The computer 8 includes an aberration measuring unit 81, an image data forming unit 82, a compensation amount determining unit 83, a voltage change template selecting unit 85, and a display unit 86. The wavefront aberration measuring unit receives reflected light reflected from the fundus 61 and measures the wavefront aberration, and includes a point image receiving optical system 5 and an aberration measuring unit 81. The control unit controls the amount of aberration correction by the compensation optical system 7 (wavefront aberration correction optical element) based on the wavefront aberration measured by the wavefront aberration measurement unit, and includes a compensation amount determination unit 83, a voltage change template selection unit 85, and an operation. A control unit 9 is provided.

  The fundus illumination system 2 includes a second light source unit 21, a condenser lens L1, and a beam splitter BS1, and illuminates a predetermined area on the retina 61 of the eye 60 to be examined with a second light beam from the second light source unit. It is. The second light source unit 21 may use, for example, a laser element that emits a red light beam having a wavelength of 630 nm as the second wavelength, and acts as a point light source or a surface light source with respect to the fundus 61, thereby making the fundus 61 a red region. it can. The beam splitter BS1 reflects the light beam from the second light source unit 21 toward the eye 60 to be examined and transmits the light beam reflected and returned by the eye 60 to be examined. For illumination of the fundus 61, for example, illumination light in the observation region of the fundus 61 may be formed using a perforated mirror. When using a perforated mirror, the perforated mirror and the pupil are in a conjugate relationship to prevent reflection at the apex of the cornea 62. Further, regarding the illumination of the fundus 61, the center of the ring-shaped stop may be 100% transmitted, and the transmittance of the peripheral region with respect to the center may be about 10%, for example, and the entire fundus 61 may be illuminated by the peripheral region.

  The fundus oculi observation system 3 includes a fundus image forming optical system 31, a fundus image light receiving unit 32 (CCD), and a fundus image display unit 33. The fundus image forming optical system 31 includes, for example, afocal lenses L2 and L3, an compensating optical system 7, a beam splitter BS2, and a condenser lens L9. The fundus image forming optical system 31 guides the light of the second wavelength reflected by the fundus 61 to the fundus image light receiving unit 32 via the adaptive optical system 7. The beam splitter BS2 is formed of a dichroic mirror that reflects a light beam having a second wavelength and transmits a light beam having a first wavelength, for example. The fundus image light receiving unit 32 receives the fundus image formed by the fundus image forming optical system 31 and displays the fundus image on the fundus image display unit 33. For example, the fundus image light receiving unit 32 emits light of the second wavelength (red light). It can be formed of a light receiving element having sensitivity.

  The point image projection optical system 4 includes a first light source unit 41 and a condenser lens L8. The first light source unit 41 preferably has a large spatial coherence and a small temporal coherence. Here, as an example, a super luminescence diode (SLD) is adopted as the first light source unit 41, and a point light source with high luminance can be obtained. The first light source unit 41 is not limited to the SLD. For example, even with a laser having a large spatial coherence or temporal coherence, by inserting a rotating diffusion plate or the like and appropriately reducing the temporal coherence, Can be used. Furthermore, even an LED with small spatial coherence and temporal coherence can be used by inserting a pinhole or the like at the position of the light source in the optical path as long as the amount of light is sufficient. The first wavelength of the illumination light beam emitted from the first light source unit 41 is, for example, an infrared wavelength (for example, 780 nm).

  The point image receiving optical system 5 includes, for example, relay lenses L6 and L7, a beam splitter BS3, a Hartmann plate 51 that is a conversion member that converts a part of the reflected light beam (first light beam) into at least 17 beams, and the Hartmann And a point image receiving optical unit 52 for receiving a plurality of beams converted by the plate 51. The point image light receiving optical system 5 is for receiving the first light beam reflected and returned from the retina 61 of the eye 60 to be guided to the point image light receiving optical unit 52. The beam splitter BS3 reflects the light beam from the first light source unit 41, reflects from the retina 61 of the eye 60 to be inspected, and transmits the reflected light beam that has returned through the compensation optical system 7 and the relay lenses L6 and L7. The Hartmann plate 51 is a wavefront conversion member that converts a reflected light beam into a plurality of beams. For example, a plurality of micro Fresnel lenses arranged in a plane orthogonal to the optical axis can be used. In general, for the measurement target portion (eye to be measured 60), to measure the spherical component of the eye to be measured 60, third-order astigmatism, and third-order and fourth-order aberrations of Zernike, It is known that measurements need to be made with at least 17 beams through the eye 60.

  FIG. 6 is an explanatory diagram of a wavefront sensor used in the point image light receiving optical system 5. The micro Fresnel lens used for the Hartmann plate 51 is an optical element, and includes, for example, an annular zone having a height pitch for each wavelength and a blaze optimized for emission parallel to the focal point. The micro Fresnel lens here is, for example, an optical path length difference of 8 levels applying a semiconductor microfabrication technique, and achieves a high light collection rate (for example, 98%). The reflected light from the fundus 61 is collected on the point image receiving optical unit 52 via the Hartmann plate 51. Here, the point image receiving optical unit 52 employs a CCD with low lead-out noise. However, as the CCD, for example, a general low noise type, a cooling CCD of 2000 × 2000 elements for measurement, or the like can be used. A type of thing can be applied. The wavefront aberration appears as a point image moving distance (Δx, Δy) in the point image receiving optical unit 52.

  Preferably, the point image projection optical system 4 and the point image light receiving optical system 5 are provided with a prism (not shown) inserted in the middle of the optical path, and by adjusting the prism position, It is good to comprise so that a light beam may be condensed with the eye 60 to be examined. In this case, assuming that the light beam from the first light source unit 41 is reflected at the point where the light is focused, the relationship in which the signal peak at the point image receiving optical unit 52 due to the reflected light is maximized is maintained, and the point image receiving optical system is maintained. The prism position is adjusted in the direction in which the signal peak at the unit 52 increases.

  The compensation optical system 7 includes deformable mirrors 71 and 72, relay lenses L4 and L5 as wavefront aberration correction optical elements that compensate the aberration of the measurement light, and a moving prism (not shown) that moves in the optical axis direction to correct the spherical component. Or a spherical lens L3 that moves in the optical axis direction to correct the spherical component. The compensating optical system 7 is disposed in the fundus oculi observation system 3 and the point image receiving optical system 5 and compensates for aberrations of reflected light flux that is reflected back from the eye 60 to be examined, for example. In addition, the compensation optical system 7 may compensate the aberration with respect to the light beam emitted from the first light source unit 41 and illuminate a minute region on the fundus 61 of the eye 60 to be examined with the light beam subjected to the aberration compensation. good.

  The deformable mirrors 71 and 72 change the wavefront of the light beam by deforming the mirror by an actuator provided inside the mirror. For example, one of the deformable mirrors 71 corrects the wavefront of the astigmatism component. The other deformable mirror 72 is preferably configured to perform wavefront correction excluding astigmatism components. As the structure of the second electrode in the deformable mirror 71 for correcting the wavefront of the astigmatism component, for example, a rectangular electrode as shown in FIG. 3D or a strip electrode shape illustrated in FIG. It can be selected as appropriate. In the case of the electrode shape of FIG. 3 (D), the manufacture becomes easy, and in the case of the strip electrode shape illustrated in FIG. 3 (E), it takes a little time to manufacture by forming it in an appropriate width. It becomes easy to form a curvature necessary for correction.

  The axis of astigmatism is adjusted by rotating the entire deformable mirror 71 (reflection film 15) attached to the stepping motor around the optical axis. This rotation angle is determined by the ratio of the Zernike coefficients of the Zernike polynomials Z (2,2) and Z (2, -2). On the other hand, in the deformable mirror 72 that performs wavefront correction excluding the astigmatism component, for example, a number of electrodes may be provided in a honeycomb shape shown in FIG. The deformable mirrors 71 and 72 include, for example, a form that is deformed by electrostatic capacity and a form that is deformed using a piezoelectric element.

  The function of the deformable mirrors 71 and 72 can be replaced by another element used as an adaptive optical system (Adaptive Optics) for compensating the aberration of the measurement light. For example, a spatial light modulator such as a liquid crystal is used. Can do. The liquid crystal spatial light modulator modulates the phase by utilizing the light distribution of the liquid crystal, and is used after being reflected in the same manner as the deformable mirror. In addition, when using a spatial light modulator, a polarizer may be needed in the middle of an optical path. In the deformable mirror and the spatial light modulator, a transmissive optical system may be used in addition to the reflective optical system.

  Next, each component of the computer 8 will be described. The aberration measuring unit 81 obtains optical characteristics including high-order aberrations of the eye 60 based on the output from the point image light receiving optical unit 52. The output from the point image light receiving optical unit 52 is reflected light from the fundus (retina) 61 and includes an aberration because the eye optical system is incomplete, and does not become a plane wave. When the light including aberration is condensed by the micro lens of the Hartmann plate 51, the condensing point is displaced. The displacement point is photographed by the point image receiving optical unit 52, and the displacement amount (Δx, Δy) is measured by the aberration measuring unit 81. In addition to the output signal from the point image receiving optical unit 52, the aberration measuring unit 81 may receive wavefront measurement data indicating at least the wavefront aberration of the eye 60 to obtain optical characteristics.

  The image data forming unit 82 performs a simulation of the appearance of the eye 60 based on optical characteristics such as wavefront aberration, and calculates simulation image data related to the appearance of the eye 60 or eye data such as MTF indicating the appearance. .

The compensation amount determining unit 83 uses the voltage change template selected by the voltage change template selection unit 85 to distribute the wavefront correction amount of the astigmatism component handled by the deformable mirror 71 and the deformable mirror 72. The correction amount excluding the astigmatism component is determined, and the correction amounts for the deformable mirrors 71 and 72 are output to the operation control unit 9. The compensation amount determining unit 83 converts the aberration Z into a Zernike polynomial from the displacement (Δx, Δy) measured by the aberration measuring unit 81, and assigns weights (a, b, c,...) To the Zernike polynomial. Put on.
Z = aZernike (1,1) + bZernike (1, -1) + cZernike (2,0) + ... (1)
The operation control unit 9 also determines the rotation angle for the deformable mirror 71 and controls the stepping motor.

  In order to correct the aberration expressed by each Zernike polynomial, a voltage applied to each electrode of the deformable mirror 72 is held as a database in, for example, the voltage change template DB6. The compensation amount determination unit 83 determines a voltage to be applied to each electrode of the deformable mirror 72 with reference to the voltage change template DB 6 and sends a correction signal to the operation control unit 9. The compensation amount determining unit 83 is preferably configured to sequentially repeat the measurement of the aberration of the eye 60 and the correction of the aberration by the deformation of the deformable mirror 72 until the aberration is equal to or less than a threshold value (for example, RMS 0.1 μm).

  Preferably, the compensation amount determining unit 83 calculates evaluation data for evaluating the quality of the fundus image based on the simulation image data or the eye characteristic data to be examined for a plurality of voltage change templates, and the evaluation data Based on this, an appropriate correction amount for the deformable mirrors 71 and 72 may be determined. As the evaluation data, for example, a value indicating the degree of matching between a simulation image and a predetermined pattern template or MTF (Modulation Transfer Function) can be used. Here, the MTF is an index indicating the transfer characteristic of the spatial frequency, and is widely used to express the performance of the optical system. For example, the MTF can be predicted in appearance by obtaining transfer characteristics for 0 to 100 sinusoidal gray gratings per degree.

  The voltage change template selection unit 85 selects a voltage change template stored in the voltage change template DB 6. The selection may be configured such that the computer 8 designates based on a predetermined selection criterion based on, for example, an operator's designation and optical characteristics such as wavefront aberration of the eye 60 to be examined. The voltage change template DB 6 stores a concentric circle template 64, a symmetric template 66, and an asymmetric template 68. The concentric circle template 64 copes with the property that the element located near the center of the deformable mirror 72 is more susceptible to the image quality than the element located near the center, and the concentric circle template 64 greatly increases the inner voltage change. It is good to set. In the symmetric template 66, a voltage change value that is symmetric with respect to the center point of the deformable mirror 72 can be set. The asymmetric template 68 sets an appropriate voltage change value that is asymmetric with respect to the center or axis. The display unit 86 is a man-machine interface such as a CRT or a liquid crystal display device.

  The operation control unit 9 deforms the deformable mirrors 71 and 72 based on the output from the compensation amount determination unit 83. Further, the operation control unit 9 moves the lens L3 in the optical axis direction based on the output from the computer 8. The fundus oculi observation device may be further provided with an alignment system (not shown) and a fixation system (not shown). The alignment system illuminates an appropriate pattern such as a placido ring and guides the light beam reflected and returned from the anterior eye portion of the eye 60 or the cornea 62 to the alignment light receiving portion. To match the pupil and the optical axis. The fixation system includes an optical path for projecting a visual target for causing fixation or clouding of the eye 60 to be measured.

(Conjugate relationship)
The fundus 61 of the eye 60 to be measured is arranged to have a substantially conjugate relationship with the first light source unit 41 and the point image light receiving optical unit 52. The surfaces of the deformable mirrors 71 and 72 are arranged to have a substantially conjugate relationship with the fundus 61 (or pupil) of the eye 60 to be measured and the Hartmann plate 51.

(Zernike analysis)
Next, Zernike analysis will be described. A method for calculating the Zernike coefficients c _i ^2j-i from a generally known Zernike polynomial will be described. The Zernike coefficient c _i ^2j−i is important for grasping the optical characteristics of the eye 60 based on the tilt angle of the light beam obtained by the point image receiving optical unit 52 via a changing member such as a Hartmann plate, for example. It is a parameter.

ただし、（Ｘ，Ｙ）はハルトマン板の縦横の座標である。 The wavefront aberration W (X, Y) of the eye 60 to be examined is expressed by the following equation using the Zernike coefficient c _i ^2j−i and the Zernike polynomial Z _i ^2j−i .

However, (X, Y) are the vertical and horizontal coordinates of the Hartmann plate.

ここで、ゼルニケ多項式Ｚ_ｉ ^２ｊ−ｉは、以下の数式で表される（より具体的な式は、例えば特開２００２−２０９８５４を参照）。

m＞0 sin
m≦0 cos

The wavefront aberration W (X, Y) is expressed by the vertical and horizontal coordinates of the point image receiving optical unit 52 (x, y), the distance between the Hartmann plate and the point image receiving optical unit 52 f, and the point image receiving optical unit 52. When the movement distance of the received point image is (Δx, Δy), the following relationship is established.

Here, the Zernike polynomial Z _i ^2j−i is expressed by the following formula (for more specific formula, see, for example, JP-A-2002-209854).

m> 0 sin
m ≦ 0 cos

ただし、Ｗ（Ｘ、Ｙ）：波面収差、（Ｘ、Ｙ）：ハルトマン板座標、（△ｘ、△ｙ）：点像受光光学部５２で受光される点像の移動距離、ｆ：ハルトマン板と点像受光光学部５２との距離。 The Zernike coefficient c _i ^2j−i can be obtained with a specific value by minimizing the square error represented by the following equation.

Where W (X, Y): wavefront aberration, (X, Y): Hartmann plate coordinates, (Δx, Δy): movement distance of the point image received by the point image receiving optical unit 52, f: Hartmann plate And the point image receiving optical unit 52.

The computer 8 calculates the Zernike coefficients c _i ^2j-i and uses them to obtain eye optical characteristics such as spherical aberration, coma aberration, and astigmatism. Further, the computer 8 calculates the aberration amount RMS _i ^2j-i by the following equation using the Zernike coefficient c _i ^2j-i .

(flowchart)
FIG. 7 is a flowchart of fundus observation in the first embodiment of the present invention. First, the fundus oculi observation device aligns the eye 60 to be examined so that the optical axis of the fundus oculi observation device coincides with the pupil 62 and the fundus oculi 61 (S102). Then, the aberration measuring unit 81 of the computer 8 sets (Xre, Yre) the position where the optical axis from the first light source unit 41 hits the fundus 61 with the macula as the origin (S104). For example, the computer 8 can acquire a fundus image from the fundus image light receiving unit 32 and detect the position of the macula and the position where the optical axis corresponds to the fundus 61 by image processing. The position of the macular can be detected using a normalized correlation method, for example, by creating a macular template in advance and storing it in a memory (not shown) of the computer 8. Further, the computer 8 displays the acquired image on the display unit 86, and the operator of the fundus oculi observation device inputs the position of the macula and the position where the optical axis corresponds to the fundus 61 from an appropriate input unit such as a pointing device. Also good.

  Next, the aberration measuring unit 81 measures the wavefront aberration of the eye 60 based on the signal from the point image receiving optical unit 52 (S108). The compensation amount determination unit 83 converts the measured aberration into a Zernike polynomial (S110). The compensation amount determination unit 83 determines a correction amount to be distributed to the two deformable mirrors 71 and 72 (S112). Then, the compensation amount determination unit 83 determines the deformable mirrors 71 and 72 to be corrected according to the distributed aberration (S114). That is, one deformable mirror 71 corrects astigmatism components, and the other deformable mirror 72 corrects aberrations other than astigmatism components such as coma and spherical aberration.

  Subsequently, the compensation amount determination unit 83 converts the voltage change template selected by the voltage change template selection unit 85 into a correction signal for the target deformable mirrors 71 and 72 (S116). The computer 8 determines whether correction signals have been calculated for all the deformable mirrors 71 and 72 (S118). In the case of No in S118, the deformable mirror to be corrected is changed and returned to S116 (S120). In the case of Yes in S118, the compensation amount determining unit 83 outputs the correction signal converted in S116 to the operation control unit 9, and the operation control unit 9 outputs the applied voltage signal to the deformable mirrors 71 and 72 (S122). . Then, each element of the deformable mirrors 71 and 72 is displaced according to the applied voltage signal, the reflecting mirror is deformed, and the axis of the deformable mirror 71 is adjusted to an appropriate angle by the control of the stepping motor. (S124).

  The computer 8 uses the aberration measuring unit 81 to measure the wavefront aberration of the eye 60 based on the signal from the point image receiving optical unit 52 (S126). The computer 8 determines whether the measured aberration is smaller than a predetermined threshold (S128). In the case of Yes in S128, the compensation amount determination unit 83 returns to S110. If No in S128, the process ends.

  The fundus oculi observation device / system of the present invention includes a fundus oculi observation program for causing a computer to execute each procedure, a computer-readable recording medium recording the fundus oculi observation program, and a fundus observation program that can be loaded into an internal memory of the computer. The program product can be provided by a computer such as a server including the program.

  The optical characteristics of the eye 60 to be examined are obtained by the aberration measuring unit 81 using the anterior eye image and the fundus image obtained by the point image receiving optical system 5, but the present invention is not limited to this. Further, it can be configured so as to be obtained from wavefront measurement data including wavefront aberration from an appropriate optical system and apparatus. In the first and second embodiments of the present invention, two deformable mirrors 71 and 72 are disposed with the mirror surfaces facing each other. However, the present invention is not limited to this, and three or more mirrors are provided. These deformable mirrors may be used.

It is a block diagram which shows an example of an electrostatic variable shape mirror. It is a top view explaining an example of the electrode arrangement | sequence of a deformable mirror which performs the wavefront correction | amendment except an astigmatism component. It is explanatory drawing of an example of the electrode arrangement | sequence of a deformable mirror suitable for performing the wavefront correction | amendment of an astigmatism (cylinder) component. It is a figure explaining an example of the rotation part which rotates the variable shape mirror for wavefront correction of a cylinder component. 1 is a configuration block diagram illustrating an example of an entire fundus oculi observation device according to the present invention. It is explanatory drawing of a wavefront sensor. It is a flowchart of fundus observation in the present invention.

Explanation of symbols

2 Fundus illumination system (second illumination optical system)
3 Fundus observation system 31 Fundus image forming optical system 32 Fundus image light receiving unit (CCD)
33 Fundus image display unit 4 Point image projection optical system 41 First light source unit 5 Point image receiving optical system 51 Hartmann plate 52 Point image receiving optical unit 6 Voltage change template DB (database)
60 Eye to be examined (object)
61 Retina (fundus)
62 Cornea (Anterior Eye)
7 Compensating optics 71, 72 Deformable mirror (wavefront aberration correcting optical element)
8 Computer 81 Aberration Measurement Unit 82 Image Data Formation Unit 83 Compensation Amount Determination Unit 85 Voltage Change Template Selection Unit 86 Display Unit 9 Operation Control Unit BS Beam Splitters L1 to L9 Lens

Claims (5)

A wavefront aberration measuring unit that receives a light beam from an object and measures wavefront aberration;
An image forming optical system that receives a light beam from the object via at least two wavefront aberration correction optical elements and forms an image of the object;
A control unit for controlling an aberration correction amount of the wavefront aberration correcting optical element based on the wavefront aberration measured by the wavefront aberration measuring unit;
An image forming apparatus comprising:
At least one of the wavefront aberration correcting optical elements performs astigmatism wavefront correction and is formed to be rotatable around the optical axis, and the other wavefront aberration correcting optical elements perform wavefront correction excluding astigmatism components. An image forming apparatus formed as described above. The object is the fundus of the eye to be examined;
An illumination optical system for illuminating the fundus of the eye to be examined;
The image forming apparatus according to claim 1, wherein the image forming optical system is configured to form an image of the fundus of the eye to be examined. The wavefront aberration correcting optical element comprises a deformable mirror;
A pair of electrodes, a first electrode provided on the deformable mirror side of the deformable mirror and a second electrode provided on the side facing the first electrode, is formed, and the first electrode and the second electrode The image forming apparatus according to claim 1, wherein the wavefront aberration correcting optical element is configured to be variable in shape according to a voltage applied to the electrode. A variable shape mirror disposed in a light path of a light beam of at least one optical system of a light receiving optical system that receives a light beam from the eye to be examined or an illumination optical system that irradiates the light beam to the eye to be examined;
A wavefront correction optical apparatus comprising: a control calculation unit that calculates a control amount of the deformable mirror necessary for correcting the aberration of the light flux wavefront;
The deformable mirror that performs wavefront correction of the astigmatism component forms a pair of electrodes, a first electrode provided on the deformable mirror side and a second electrode provided on the side facing the first electrode. The wavefront aberration correcting optical element is configured to be variable in shape by the voltages applied to the first electrode and the second electrode, and the deformable mirror is rotated around the optical axis. 1. A wavefront correcting optical apparatus comprising: a deformable mirror rotating unit to be moved.   The deformable mirror that performs wavefront correction of the astigmatism component has a strip-like electrode shape, and the width near the center of each strip electrode is narrower than the vicinity of the edge, or each strip electrode has an equal width. 5. The wavefront correcting optical apparatus according to claim 4, wherein

Images