JP2011115507A - Retinal function measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To preferably detect a retinal endogenous signal of the human eye. <P>SOLUTION: This retinal function measuring apparatus for measuring the retinal function includes: an OCT optical system; an optical scanner disposed in an optical path of the OCT optical system to vary the advancing direction of measuring light beam for scanning the measuring light beam in the transverse direction on a fundus of the examined eye; and a stimulating light irradiating means for irradiating the fundus with stimulating light. The apparatus further includes: a photographing control means for controlling the OCT optical system, the optical scanner and the stimulating light irradiating means, continuously scanning a certain scanning range of the fundus, and continuously acquiring a fundus tomographic image before and after retinal stimulation for a predetermined time; a positional shifting detecting means for detecting shifting of scanning position on the fundus simultaneously with acquiring the fundus tomographic image; and a scanning position correcting means for correcting the scanning position of the measuring light on the fundus at any time so that shifting of the scanning position is corrected based on a detection signal output from the positional shifting detecting means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for photographing the fundus and measuring the function of the retina.

  A device that measures retinal function by acquiring tomographic images of the fundus before and after stimulation of the retina by stimulating light using an optical coherence tomography (OCT) optical system, calculating these tomographic images and extracting intrinsic signals of the retina. (See Patent Document 1).

JP 2007-202952 A

  However, under wakefulness, eye movement of the eye to be examined occurs, and there is a possibility that a part other than the measurement target is evaluated. In addition, in order to accurately detect a temporal change in the retinal intrinsic signal caused by light stimulation, it is necessary to continuously measure the same tomographic site on the fundus for a predetermined time (for example, about 10 seconds).

  In view of the above problems, an object of the present invention is to provide a retinal function measuring device that can suitably detect a retinal intrinsic signal of the human eye.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) The light beam emitted from the light source is divided into the measurement light beam and the reference light beam, the measurement light beam is guided to the fundus of the eye to be examined, the reference light beam is guided to the reference optical system, and then the measurement light beam reflected from the fundus and the reference light beam are combined. An interference optical system that causes the light receiving element to receive the interference light obtained by
An optical scanner that is arranged in the optical path of the interference optical system and changes the traveling direction of the measurement light beam in order to scan the measurement light beam in a transverse direction on the fundus of the eye to be examined;
In a retinal function measuring device comprising a stimulation light irradiation means for irradiating stimulation light to the fundus of the eye to be examined, and measuring a retinal function of the eye to be examined.
The interferometric optical system, the optical scanner, and the stimulation light irradiation unit are controlled to continuously scan a scanning range with the fundus of the eye to be examined, and tomographic images of the fundus before and after retinal stimulation are determined based on signals from the light receiving element. Photographing control means for acquiring time continuously;
A light receiving optical system that irradiates the fundus of the eye to be examined with a second light flux and causes the second light receiving element to receive the second light flux reflected by the eye fundus of the eye to be examined; A displacement detection means for detecting a displacement of the scanning position on the fundus based on a light reception signal from the second light receiving element;
Based on a detection signal output from the positional deviation detection means, the driving of the optical scanner or a second optical scanner installed separately from the optical scanner is controlled, so that the deviation of the scanning position is corrected. And a scanning position correcting means for correcting the scanning position of the measuring light at any time.
(2) In the retinal function measuring device of (1),
The interference optical system and the light receiving optical system are formed so that wavelength bands of the measurement light beam and the second light beam are different from each other.
(3) In the retinal function measuring device of (2),
The positional deviation detecting means is
A fundus imaging optical system that images a fundus front image of the eye to be examined by the second light receiving element;
Based on an output signal from the second light receiving element, a front image of the fundus of the eye to be examined is acquired at any time, and a measurement image acquired at any time is compared with a reference image acquired in advance to detect a shift in the scanning position. It is characterized by doing.
(4) In the retinal function measuring device of (3),
The positional deviation detection means sets at least one image region selected as a characteristic region in the fundus front image as a template image, and a template for a measurement image acquired at any time using each template image Matching is performed, and the shift of the scanning position is detected based on the coordinate position of the template image in the measurement image.
(5) In the retinal function measuring device of (4),
The positional deviation detection means sets an image region corresponding to each point including at least one point on a scan line set in advance for the fundus front image as a template image.
(6) In the retinal function measuring device of (5),
The misregistration detection means sets an image area corresponding to each point including at least two points on the scan line as a template image,
The scanning position correcting means detects the shift of the scanning position based on the coordinate position of the template image in the measurement image.
(7) In the retinal function measuring device of (6),
The at least two points on the scan line include a start point and an end point of the scan line.
(8) In the retinal function measuring device of (5),
The misregistration detection means further sets at least two or more image areas separated from the scan line as a template image, and stores in advance the positional relationship between the template image and the scan line,
The scanning position correction unit detects a shift of the scanning position based on the coordinate position of the template image in the measurement image and the positional relationship stored in advance.
(9) In the retinal function measuring device of (4),
The positional deviation detection means updates the search area at the time of performing template matching with respect to the fundus front image based on the coordinate position of the template image detected at any time.

  According to the present invention, it is possible to suitably detect the retinal intrinsic signal of the human eye.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an optical system of a retinal function measuring apparatus according to this embodiment.

  In FIG. 1, the optical system of the present apparatus receives an observation illumination optical system 10 that illuminates a retinal region of a subject's eye E, and reflected light from the retinal region illuminated by the observation illumination optical system 10 to receive a fundus image. A light receiving optical system (fundus observation optical system) 20 for obtaining the eye, a stimulating light irradiation optical system 30 for stimulating the retina by irradiating the retina region of the subject's eye, and the subject's eye It is roughly divided into a fixation optical system 40 for making a fixation and an interference optical system (OCT optical system) 200 for taking a tomographic image in the retinal region of the eye E.

  The observation illumination optical system 10 has an observation light source 11 such as a halogen lamp, for example, an infrared filter 12 that transmits infrared light having a wavelength of 800 nm to 900 nm, a condenser lens 13, and a characteristic that reflects infrared light and transmits visible light. It includes a dichroic mirror 14 having a ring, a ring slit 15 having a ring-shaped opening, a light projecting lens 16, a perforated mirror 17, and an objective lens 18. The ring slit 15 and the perforated mirror 17 are disposed at a position substantially conjugate with the pupil of the subject's eye E. The observation illumination light emitted from the observation light source 11 is converted into an infrared beam by the infrared filter 12, collected by the condenser lens 13, and then reflected by the dichroic mirror 14 to illuminate the ring slit 15. The light transmitted through the ring slit 15 reaches the perforated mirror 17 through the light projecting lens 16. Most of the light reflected by the mirror portion of the perforated mirror 17 is once converged in the vicinity of the pupil of the subject eye E via the dichroic mirror 60 and the objective lens 18, and then diffused to the subject eye. A predetermined area of E's retina is illuminated continuously.

  The stimulation light irradiation optical system 30 is a stimulation light source 31 (for example, a flash lamp, a visible LED, etc.) that emits visible flash light for stimulating the retinal region, a condensing lens 33, the observation illumination optical system 10, and an optical path. Including an optical system from the ring slit 15 to the objective lens 18 sharing the same. The light source for stimulation can irradiate visible flash light in a single shot or in a flicker form. Here, the visible flash light emitted from the stimulation light source is irradiated to the retinal region of the eye E through the condenser lens 33 and the dichroic mirror 14 through the same optical path as the observation illumination light.

  The light receiving optical system 20 includes an objective lens 18, a focusing lens 21 movable in the optical axis direction, an imaging lens 22, and a two-dimensional light receiving element 23 (for example, a two-dimensional CCD sensor). The focusing lens 21 moves in the optical axis direction by driving the drive mechanism 50. Reflected light from the retinal region illuminated by the observation light source 11 is once condensed in front of the perforated mirror 17 via the objective lens 18 and the dichroic mirror 60, and then passes through the opening of the perforated mirror 17. Then, the reflected light that has passed through the aperture (hole portion) of the perforated mirror 17 is condensed by the imaging lens 22 via the focusing lens 21 and then imaged on the two-dimensional light receiving element 23. The light receiving optical system 20 forms a fundus camera optical system that receives a light beam reflected from the fundus of the subject's eye by a two-dimensional imaging device and photographs a fundus front image of the subject's eye.

  The fixation optical system 40 includes a fixation light source 41 that emits visible light, a pinhole (or a fixation chart) 42, and a dichroic mirror 29 that reflects visible light and transmits infrared light. The optical path from 29 to the objective lens 18 is shared with the light receiving optical system 20. The pinhole 42 is arranged at a position substantially conjugate with the observation point (imaging point) of the retina of the subject's eye E. The light emitted from the fixation light source 41 passes through the pinhole 42, is reflected by the dichroic mirror 29, and then passes through the optical path in the direction opposite to the reflected light from the retina (imaging lens 22 to objective lens 18). An image is formed on the retina of the examiner's eye.

  The dichroic mirror 60 is used as a light splitting member that splits the optical path of the light receiving optical system 20 and the optical path of the OCT optical system 200, and the measurement light emitted from the measurement light source 27 used in the OCT optical system 200 (for example, λ = 1000 to 1000). 1100 nm) and transmits other light. That is, the interference optical system 200 and the light receiving optical system 20 have different wavelengths for the measurement light (first light beam) used for acquiring the tomographic image and the illumination light (second light beam) used for acquiring the fundus front image. It is formed to be a band. Thereby, interference of measurement light and illumination light is avoided, and a retinal tomogram and a fundus front image can be suitably measured. Note that the dichroic mirror 60 may have a characteristic of transmitting infrared light with a wavelength of 800 nm to 900 nm (instead of the infrared filter 12) and a characteristic of transmitting visible light. In addition, the interference optical system 200 and the light receiving optical system 20 may use the same wavelength band. In this case, a half mirror may be used instead of the dichroic mirror 60.

  Next, the configuration of the OCT optical system 200 provided on the reflection side of the dichroic mirror 60 will be described. The interference optical system 200 divides the light beam emitted from the light source into a measurement light beam and a reference light beam, guides the measurement light beam to the fundus of the eye to be examined, guides the reference light beam to the reference optical system, and then reflects the measurement light beam and the reference light beam reflected by the fundus. Interference light obtained by the combination with is received by the light receiving element.

  Reference numeral 27 denotes an OCT light source that emits low-coherent light used as measurement light and reference light of the OCT optical system 200. For example, an SLD light source is used. For the OCT light source 27, for example, a light source having a center wavelength of 1050 nm and a bandwidth of 50 nm is used. Reference numeral 26 denotes a fiber coupler (beam splitter) that doubles as a light splitting member and a light coupling member. Light emitted from the OCT light source 27 is split into reference light and measurement light by the fiber coupler 26 via an optical fiber 67 as a light guide. The measurement light goes to the eye E through the optical fiber 64, and the reference light goes to the reference mirror 28 through the optical fiber 65.

  In the optical path for emitting the measurement light toward the eye E, the optical fiber 64 for emitting the measurement light, the focusing lens 63 movable in the optical axis direction according to the refraction error of the eye to be examined, and the scanning drive mechanism 51 are driven. A scanning unit 62 composed of a combination of two galvanometer mirrors capable of scanning measurement light in the XY directions on the fundus and a relay lens 61 are arranged. The dichroic mirror 60 and the objective lens 18 serve as a light guide optical system that guides the OCT measurement light from the OCT optical system 200 to the fundus of the eye to be examined. Note that the scanning unit 62 of the present embodiment has a configuration in which the scanning direction of the measurement light to be scanned on the fundus can be arbitrarily set by arbitrarily adjusting the reflection angle of the measurement light by the two galvanometer mirrors. Yes. Therefore, it is possible to obtain a tomographic image of an arbitrary region of the fundus of the eye to be examined. Note that the end of the optical fiber 64 is disposed so as to be conjugate with the fundus of the eye to be examined. Further, the two galvanometer mirrors of the scanning unit 62 are arranged at a position substantially conjugate with the eye pupil to be examined.

  The galvanometer mirror and scanning drive mechanism 51 are arranged in the optical path of the interference optical system 200, and change the traveling direction of the measurement light beam in order to scan the measurement light beam in the transverse direction (XY direction) on the fundus of the eye to be examined ( Used as an optical scanning unit). The optical scanner uses an acousto-optic device (AOM) that changes the traveling (deflection) direction of light in addition to a mirror.

  The measurement light emitted from the optical fiber 64 reaches the scanning unit 62 via the focusing lens 63, and the reflection direction is changed by driving the two galvanometer mirrors. Then, the measurement light reflected by the scanning unit 62 is reflected by the dichroic mirror 60 via the relay lens 61 and then condensed on the fundus of the eye to be examined via the objective lens 18.

  Then, the measurement light reflected from the fundus is reflected by the dichroic mirror 60 via the objective lens 18, travels to the OCT optical system 200, passes through the relay lens 61, the two galvanometer mirrors of the scanning unit 62, and the focusing lens 63. , Enters the end of the optical fiber 64. The measurement light incident on the optical fiber 63 reaches the end of the optical fiber 66 via the fiber coupler 26 and the optical fiber 66.

  On the other hand, an optical fiber 65 that emits reference light, a collimator lens 25, and a reference mirror 28 are arranged in an optical path that emits the reference light toward the reference mirror 28. The reference mirror 28 is configured to be movable in the optical axis direction by the reference mirror driving mechanism 52 in order to change the optical path length of the reference light. The reference optical system is not limited to the reflection type, but may be a transmission type optical system.

  The reference light emitted from the end of the optical fiber 65 is converted into a parallel light beam by the collimator lens 25, reflected by the reference mirror 28, condensed by the collimator lens 25, and incident on the end of the optical fiber 65. The reference light incident on the optical fiber 65 reaches the fiber coupler 26.

  Then, the reference light generated as described above by the light emitted from the light source 27 and the fundus reflection light by the measurement light irradiated on the eye fundus to be examined are combined by the fiber coupler 26 to be interference light, The light is emitted from the end of the fiber 66. A spectroscopic optical system 800 (spectrometer unit) 800 separates interference light into frequency components in order to obtain an interference signal for each frequency, and includes a collimator lens 80, a grating mirror (diffraction grating) 81, a condensing lens 82, and a light receiving element. 83. The light receiving element 83 uses a one-dimensional element (line sensor) having sensitivity in the wavelength band of the OCT light source.

  Here, the interference light emitted from the end of the optical fiber 66 is converted into parallel light by the collimator lens 80, and then is split into frequency components by the grating 81. Then, the interference light split into frequency components is condensed on the light receiving surface of the light receiving element 83 via the condenser lens 82. Thereby, spectrum information of interference fringes is recorded on the light receiving element 83. Then, the spectrum information is input to the control unit 70 and analyzed using Fourier transform, whereby information (A scan signal) in the depth direction of the subject's eye can be measured. Here, the control unit 70 can acquire a tomographic image by causing the scanning unit 62 to scan the measurement light on the fundus in a predetermined transverse direction. That is, by scanning in the XY direction, a tomographic image in the Z direction on the XY plane can be acquired (in this embodiment, a method for obtaining a tomographic image by performing one-dimensional scanning with the measurement light on the fundus in this way. Is B scan). The acquired tomographic image is stored in a memory 72 connected to the control unit 70. Furthermore, it is also possible to acquire a three-dimensional image of the fundus of the eye to be examined by two-dimensionally scanning the measurement light in the XY direction. The acquisition of the OCT image in the present embodiment is performed by two galvanometer mirrors provided in the scanning unit 62. In the above description, SD-OCT is taken as an example. However, the present invention is not limited to this, and SS-OCT (swept source OCT) and TD-OCT (Time domain OCT) may be used.

  The control unit 70 controls the entire apparatus. In the control unit 70, the observation light source 11, the stimulus light source 31, the fixation light source 41, the focus drive mechanism 50, the image pickup device 23, the scan drive mechanism 51, the reference mirror drive mechanism 52, and the focusing lens 63 are moved in the optical axis direction. For this purpose, a first drive mechanism 63a, a light receiving element 83, a memory (storage unit) 72, and a control unit 74 are connected. The control unit 70 also has a function as an image processing unit for imaging the eye fundus of the subject and imaging the retinal function. Reference numeral 75 denotes a monitor which is display-controlled by the control unit 70. The memory 72 is for storing various information. The control unit 74 is for performing various input operations. For example, a mouse is connected to the control unit 74.

  Here, the control unit 70 forms a fundus tomographic image by image processing based on the light reception signal output from the light receiving element 83, and forms a fundus front image by image processing based on the image pickup signal output from the imaging element 23. Form (see FIG. 2). In addition, acquisition of a tomographic image and acquisition of a fundus front image are performed in parallel. The frame rate of the image sensor 23 is set in accordance with the frame rate at the time of acquiring a tomographic image. For example, it is set to 30 fps to 50 fps.

  Further, the control unit 70 controls the interference optical system 200, the galvano mirror and the scanning drive mechanism 51, and the stimulation light irradiation optical system 30, continuously scans the scanning range where the eye fundus is examined, and receives a signal from the light receiving element 83. Based on the above, tomographic images of the fundus before and after the retinal stimulation are continuously acquired for a predetermined time.

<Scanning position setting>
First, the examiner performs alignment so that the front image Gf is displayed on the monitor 75 using a joystick (not shown). Next, the examiner moves the scan line SL electronically displayed on the front image Gf, and sets the scanning position of the measurement light (see FIG. 2A). The scanning position of the measurement light and the driving position of the galvano mirror are associated in advance.

  FIG. 3 is a diagram illustrating a specific example of the flow of tomographic image measurement and eye tracking. FIG. 4 is a diagram for explaining template matching.

<Preparation for template matching>
The examiner views the front image Gf on the monitor 75, moves the rectangular graphic, and selects at least one or more characteristic regions (for example, nipples and blood vessels) capable of pattern matching (FIG. 4A). reference). As an initial setting, the control unit 70 may automatically detect a nipple included in the front image by image processing, and an image region near the nipple may be automatically set as a characteristic part.

<Image acquisition start and template image registration>
When a trigger signal for starting imaging is issued, the control unit 70 drives the galvanometer mirror based on the set scanning position information (see the scan line SL), and based on the light reception signal from the light receiving element 83, the tomographic image is generated. Is stored in the memory 72.

  The control unit 70 registers one image (first front image) at the start of measurement output from the image sensor 23 as a reference image, and at least one image region selected as a characteristic region. It registers as a template image (B1-B4) (refer Fig.4 (a)). In this case, the center coordinates (see small circles in the figure) of the images B1 to B4 are calculated, and a predetermined image area centered on each center coordinate becomes a template. And it is used for the template matching with respect to the output image from the image pick-up element 23. FIG.

  At this time, the control unit 70 sets the search areas S1 to S4 around the center coordinates of the images B1 to B4 as the search range when performing template matching. Note that the search areas S1 to S4 have a wider range than the images B1 to B4, and are set to have the same size (or more) as the average movement range of the eyes due to microscopic fixation during acquisition of an image for one frame. Is done.

<Template matching>
Thereafter, the control unit 70 performs template matching on the measurement image acquired as needed using each of the template images (B1 to B4) described above, and shifts the scanning position based on the coordinate position of the template image in the measurement image. To detect.

  More specifically, when the tomographic image of the first frame is acquired, the control unit 70 further drives the galvano mirror to start acquiring the tomographic image (second tomographic image) of the next frame. Further, when the measurement image (second fundus front image) of the next frame is acquired, template matching (evaluation by cross-correlation analysis between the reference image and the measurement image) is performed on the determined template image and the measurement image ( (Refer FIG.4 (b)). As an evaluation function in template matching, SSD (Sum of Squared Difference) indicating similarity or SAD (Sum of Absolute Difference) indicating difference may be used as the evaluation function.

  The control unit 70 moves the images B1 to B4 horizontally / vertically / rotates within the above-described search areas S1 to S4 (see FIG. 4A) in the measurement image data, and detects a location where the correlation value is maximized. . And the control part 70 obtains the location where a correlation value becomes the maximum regarding each template image B1-B4 as a center coordinate position (refer FIG.4 (b)). Then, the control unit 70 calculates movement information (for example, movement direction and movement amount) of the center coordinate positions of the images B1 to B4 in the reference image and the measurement image, and obtains the average as the eyeball movement information ΔP.

<Setting the next scanning position>
Next, the control unit 70 obtains the tomographic image (third tomographic image) of the next frame based on the positional deviation detection signal (eye movement information ΔP) detected as described above. A scanning position is set in advance. More specifically, the control unit 70 corrects the scan start point and end point (see the scan line SL) set for the reference image based on the calculated eye movement information ΔP. In this case, a scanning position obtained by adding movement information ΔP to each of the scanning start point and end point in the reference image is set as the correction position.

  Further, the area obtained by adding the movement information ΔP to the search areas S1 to S4 in the reference image is reset as the search area of the next frame. In this case, the search areas S1 to S4 may be corrected based on the center coordinate positions of the images B1 to B4 in the measurement image and reset as the search area of the next frame.

<Acquisition of tomographic image using corrected scanning position information>
When acquiring a tomographic image (third tomographic image) of the next frame, the tomographic image is obtained by driving the galvanometer mirror based on the scanning position information corrected as described above. In this case, a galvanometer mirror drive signal is output based on the start point position corrected as described above, and scanning of the measurement light with respect to the retina is started. Then, the measurement light scans a certain scanning range set on the fundus, and the measurement light scan ends at the corrected end point position. The tomographic image is stored in the memory 72. Thereby, the shift of the scanning position on the fundus due to the fine movement of the eye to be examined is corrected.

<Real time tracking>
Further, when the measurement image (third fundus front image) of the next frame is acquired, the control unit 70 further performs template matching for the third fundus front image in each of the reset search areas S1 to S4. To obtain eye movement information ΔP in the same manner as described above. Then, based on the eye movement information ΔP, the starting point and the ending point of scanning when further acquiring a tomographic image (fourth tomographic image) of the next frame are corrected. Thereafter, the control unit 70 drives the galvanometer mirror based on the corrected scanning position to obtain a fourth tomographic image. Then, the tomographic image is stored in the memory 72.

  As described above, the control unit 70 performs eye tracking (tracking) of measurement light by sequentially performing template matching and scan line determination by image processing. That is, the control unit 70 obtains a fundus front image at any time based on an output signal from the image sensor 23 at a predetermined frame rate, compares the measurement image obtained at any time with the reference image, and moves the eye movement information ΔP ( Scan position deviation information) is detected. Then, the scanning position of the measurement light is corrected as needed based on the detected eye movement information ΔP, and a tomographic image is obtained based on the corrected scanning position (active tracking). Moreover, the search area | region at the time of performing template matching is updated at any time based on the coordinate position of each template image B1-B4 in the front image acquired at any time.

  At the time of the active tracking, the control unit 70 controls the light source 31 to irradiate the eye to be examined with a preset condition (for example, single flash light, flicker light, etc.), Stimulates the retina of eye E. As a result, the cells constituting the retina are stimulated, and the activity of nerve cells based on this is caused.

<External signal extraction>
When the continuous acquisition of tomographic images within a predetermined time is completed as described above, the control unit 70 obtains a change in the brightness (luminance) of the tomographic image stored in the memory 72 for each pixel. The change in brightness can be obtained by obtaining a difference or a ratio. By calculating the change in the luminance value of the tomographic image in this way, an intrinsic signal is extracted. The control unit 70 displays brightness change information on the monitor 75 in association with each pixel.

  For example, the control unit 70 adds and averages a plurality of tomographic images acquired within a predetermined time (for example, 2 seconds) before retinal stimulation, and within a predetermined time (for example, stimulation) after retinal stimulation. You may make it obtain | require the change information of the brightness | luminance of the addition average image which carried out the average of the several tomographic image acquired in after 8 second). When the number of tomographic images before and after stimulation is the same, an addition image may be used instead of the addition average image.

  In addition, the control unit 70 may calculate the temporal change of the luminance value at a certain part in the tomographic image acquired over time and display the calculation result (for example, a graph, a table, etc.). Examples of the luminance value for obtaining a temporal change include an average value of luminance values corresponding to a certain retinal layer such as a photoreceptor layer, a luminance value in a minute region on the retina, and the like.

  As described above, the tomographic image of the same part can always be measured even when eye movement occurs by capturing an eye ball moving at high speed in real time by moving image processing and instantaneously feeding it back to the galvanometer mirror.

  Thereby, since the tomographic image in the same part of the fundus can be continuously measured for a predetermined time, the intrinsic signal of the retina in the depth direction can be suitably detected.

  Hereinafter, a calculation method for detecting the shift of the scanning position in consideration of the eyeball rotation will be described. As a first method, as shown in FIG. 5A, the control unit 70 sets the template images B1 and B2 around the start point and end point on the scan line SL, and sets the search areas S1 to S2. Set.

  Here, as shown in FIG. 5B, when the eyeball rotates, the fundus region including the scanning start point and the fundus region including the scanning end point are rotated around the rotation axis of the eye E. Therefore, the control unit 70 performs template matching on the measurement image of the next frame output from the image sensor 23 using the template images B1 and B2 set on the scan line SL, and correlates the template images. The center coordinate position where the value is maximum is calculated. Thereby, the deviation of the scanning position is detected.

  Here, when the measurement image of the next frame is acquired from the image sensor 23, the control unit 70 sets the center coordinate position of each of the template images B1 and B2 in the measurement image as the start point / end point of the next scan, and then The tomographic image is obtained by driving the galvanometer mirror based on the corrected scanning position data. Also, the search area is reset as described above.

  As described above, the control unit 70 detects the displacement of the scanning position by detecting the positional information of the fundus site including the start point of the scan and the fundus site including the end point of the scan for each measurement image. Then, the scanning position of the measurement light is corrected as needed based on the positional deviation information. In this case, the shift of the scanning position between the reference image and the measurement image may be calculated, and the scanning position may be corrected based on this.

  As described above, by performing template matching on the measurement image using the template image including an arbitrary point on the scan line SL as described above, the scanning position of the measurement light and the scanned fundus region are associated with each other. It is done. Therefore, smooth active tracking is possible. Further, it is possible to correct the shift of the scanning position due to the eyeball rotation without obtaining the rotation angle based on the rotation axis of the eye E.

  Furthermore, by setting an image region including the start point and end point on the scan line SL as a template image, it is possible to accurately detect a shift in the scan position due to rotation.

  Note that not only the start point and end point, but also an image region for each point may be set as a template image with at least one point on the scan line SL as a center. In addition, template images may be set based on three or more points.

  When the template image is set at a position other than the start point and end point on the scan line SL, a straight line passing through the center coordinates of each template image calculated by the template matching may be set as the next scan line.

  Next, the second method will be described with reference to FIG. In this case, the control unit 70 sets an image region centered on at least one point (for example, the start point) on the scan line SL set in advance for the fundus front image as a template image. Further, the control unit 70 sets template images B2 and B3 centering on two points E and F that are characteristic parts capable of pattern matching and are separated from the scan line SL (see FIG. 6A). Further, each search area S1 to S3 is set. In addition, about the setting position of the point E and the point F, it is preferable to form so that the line segment EF which connects these, and the scanning line SL may cross | intersect.

  Further, the control unit 70 calculates the intersection point G of the line segment EF connecting the center coordinate E of the template B2 and the center coordinate F of the template B3 and the scan line SL, and the position information of the intersection point G with respect to the feature points E and F (For example, the distance between the line segments CE and ED, the ratio between the line segments CE and ED, etc.) is stored in the memory 75.

  And the control part 70 performs template matching with respect to the measurement image of the next flame | frame output from the image pick-up element 23 using each template image B1-B3, and the center coordinate position where a correlation value becomes the maximum about each template image. Is calculated.

  Here, when the measurement image of the next frame is acquired, the control unit 70 sets the center coordinate position C of the image B1 in the measurement image as the start point position of the next scan (see FIG. 6B).

  Further, the control unit 70 calculates the end point position of the next scan using the center coordinate positions E and F of the images B2 and B3 in the measurement image and the intersection H in the measurement image. Here, the center coordinate positions E and F corresponding to the images B2 and B3 in the measurement image represent the positions of the feature points E and F in the measurement image. When obtaining the intersection position H corresponding to the intersection G of the first front image (reference image) in the measurement image, the relationship (distance / ratio) between the line segments EG and GF in the reference image and the line segment EH in the measurement image A point where the HF relationship is the same is calculated from the line segment EF of the measurement image and set as the position of the intersection H.

  When the end point D of the next scan is obtained, the point where the relationship between the line segment CG / GD in the reference image and the relationship between the line segment CH / HD in the measurement image is the same as the line segment CH of the measurement image. Calculate from the extension line and set as the end point position D.

  Then, when the start point / end point of the next scan is set as described above, the control unit 70 drives the galvanometer mirror based on the corrected scan position data to obtain a tomographic image. Also, the search area is reset as described above.

  That is, the control unit 70 sets at least two or more image regions apart from the preset scan line SL for the fundus front image as the template images B2 and B3, and the template images B2 and B3 and the scan line. The positional relationship with SL is stored in the memory 75 in advance. Then, the control unit 70 detects the shift of the scanning position based on the positional relationship between the template images B2 and B3 and the scan line SL stored in the memory 75 and the coordinate position of the template image in the measurement image. Thereby, even if a characteristic pattern does not exist in the vicinity of the start point or end point of scanning, it is possible to detect a shift in the scanning position due to eyeball rotation.

  In the above configuration, when there is no characteristic pattern near both the end point and the start point of scanning, in addition to the intersection point G of the line segment EF connecting the feature point EF and the scan line SL, a line with respect to the scan line SL is used. The angle of the minute EF is stored in advance.

  The control unit 70 then determines the position of the intersection point G on the line segment EF in the reference image and the angle of the line segment EF with respect to the scan line SL, and the position of the intersection point H on the line segment EF in the measurement image and the line segment with respect to the scan line SL. The start point and end point of scanning in the measurement image may be set so that the angle of EF has the same relationship.

  In the above description, the scanning position is corrected by template matching using three template images. However, four or more template images may be used (however, it takes much time for matching). For example, an image centered on each point of the start point and end point of the scan line and two feature points separated from the scan line can be considered. In this case, each point may be determined from a template arranged concentrically as shown in FIG.

  In the above description, the image region corresponding to each point is set as a template image with an arbitrary point on the scan line SL as a center. However, the present invention is not limited to this, and each point including an arbitrary point on the scan line SL. As long as the image area corresponding to is set as a template image.

  In the above description, as a configuration for detecting the shift of the scanning position due to the eyeball movement of the eye to be examined, an illumination optical system that simultaneously illuminates the entire fundus with infrared light, and an imaging optical system that simultaneously images the entire fundus And an optical system having For this reason, the shift | offset | difference by the eyeball movement of the fundus front image used for position shift detection decreases. Therefore, it is possible to detect the displacement with high accuracy.

  Note that the configuration for detecting the deviation of the scanning position is not limited to the above configuration, and a light beam reflected on the fundus of the eye to be examined is received through a confocal aperture disposed at a position substantially conjugate with the fundus of the eye to be examined. Thus, a confocal optical system (SLO optical system) that captures a confocal front image of the fundus of the eye to be examined may be used.

  In addition, as described above, when the light receiving optical system for detecting the positional deviation is configured to capture a front image of the fundus of the eye to be examined, the narrower observation range can increase the speed of the positional deviation detection, and the positional deviation correction ( Tracking) can be speeded up. For example, an optical system having an imaging angle of view that matches the nipple portion of the fundus can be considered.

  Furthermore, the configuration for detecting the positional shift of the fundus of the subject's eye is not limited to the above configuration, and a second light beam different from the measurement light of the interference optical system 200 is irradiated on the fundus of the subject's eye and reflected by the fundus of the subject's eye. A light receiving optical system that causes the second light receiving element to receive the second light flux, and simultaneously acquiring a tomographic image of the fundus, and simultaneously shifting the scanning position on the fundus based on the light receiving signal from the second light receiving element. Any configuration can be used. For example, the detection light beam may be scanned using a pair of mirrors so as to draw a circle on the fundus, and the fundus reflection light may be received by a light receiving element to obtain a position shift signal (US Pat. No. 5,943,115). Issue).

  In the above description, the driving of the two galvanometer mirrors of the scanning unit 62 is controlled based on the output detection signal, and the scanning position of the measurement light on the fundus is corrected as needed so that the shift of the scanning position is corrected. However, it is not limited to this. That is, apart from the two galvanometer mirrors of the scanning unit 62, a new pupil conjugate position is formed in the optical path of the interference optical system 200, and a second optical scanner for correcting the scanning position is installed at that position. Also good.

  In the above configuration, according to the imaging optical system that captures a front image of the fundus of the eye to be examined, a front image within a predetermined time before and after retinal stimulation is continuously obtained while acquiring a tomographic image. Therefore, the control unit 70 may obtain a change in brightness (luminance) of the tomographic image of the front image stored in the memory 72 for each pixel and extract an intrinsic signal using the front image. Thereby, the intrinsic signal of the retina in the depth direction and the intrinsic signal of the retina in the plane direction can be detected simultaneously. In addition, detection of endogenous signals in the planar direction can provide a fundus map relating to retinal function, and is useful information for diagnosis.

It is a schematic block diagram which shows the optical system of the retinal function measuring apparatus which concerns on this embodiment. It is a figure which shows the specific example of the front image and tomographic image which were acquired by this optical system. It is a figure which shows the specific example of the measurement of a tomographic image, and the flow of eye tracking. It is a figure explaining template matching. It is a figure explaining the 1st method of detecting the shift of a scanning position in consideration of eyeball rotation. It is a figure explaining the 2nd method of detecting the shift of a scanning position in consideration of eyeball rotation. It is a figure at the time of providing a template concentrically.

DESCRIPTION OF SYMBOLS 20 Light reception optical system 30 Stimulation light irradiation optical system 62 Scanning part 70 Control part 200 Interference optical system

Claims (9)

The light beam emitted from the light source is divided into the measurement light beam and the reference light beam, the measurement light beam is guided to the fundus of the eye to be examined, the reference light beam is guided to the reference optical system, and then obtained by combining the measurement light beam reflected by the fundus and the reference light beam. An interference optical system that causes the light receiving element to receive the interference light;
An optical scanner that is arranged in the optical path of the interference optical system and changes the traveling direction of the measurement light beam in order to scan the measurement light beam in a transverse direction on the fundus of the eye to be examined;
In a retinal function measuring device comprising a stimulation light irradiation means for irradiating stimulation light to the fundus of the eye to be examined, and measuring a retinal function of the eye to be examined.
The interferometric optical system, the optical scanner, and the stimulation light irradiation unit are controlled to continuously scan a scanning range with the fundus of the eye to be examined, and tomographic images of the fundus before and after retinal stimulation are determined based on signals from the light receiving element. Photographing control means for acquiring time continuously;
A light receiving optical system that irradiates the fundus of the eye to be examined with a second light flux and causes the second light receiving element to receive the second light flux reflected by the eye fundus of the eye to be examined; A displacement detection means for detecting a displacement of the scanning position on the fundus based on a light reception signal from the second light receiving element;
Based on a detection signal output from the positional deviation detection means, the driving of the optical scanner or a second optical scanner installed separately from the optical scanner is controlled, so that the deviation of the scanning position is corrected. A retinal function measuring device comprising: scanning position correcting means for correcting the scanning position of the measuring light as needed. In the retinal function measuring device according to claim 1,
The interference optical system and the light receiving optical system are formed such that the wavelength bands of the measurement light beam and the second light beam are different from each other. The retinal function measuring device according to claim 2,
The positional deviation detecting means is
A fundus imaging optical system that images a fundus front image of the eye to be examined by the second light receiving element;
Based on an output signal from the second light receiving element, a front image of the fundus of the eye to be examined is acquired at any time, and a measurement image acquired at any time is compared with a reference image acquired in advance to detect a shift in the scanning position. A retinal function measuring device. The retinal function measuring device according to claim 3,
The positional deviation detection means sets at least one image region selected as a characteristic region in the fundus front image as a template image, and a template for a measurement image acquired at any time using each template image A retinal function measuring device that performs matching and detects a shift of the scanning position based on a coordinate position of the template image in the measurement image. The retinal function measuring device according to claim 4,
The retinal function measuring apparatus according to claim 1, wherein the positional deviation detecting means sets an image region corresponding to each point including at least one point on a scan line set in advance for a fundus front image as a template image. In the retinal function measuring device according to claim 5,
The misregistration detection means sets an image area corresponding to each point including at least two points on the scan line as a template image,
The retinal function measuring device according to claim 1, wherein the scanning position correcting unit detects a shift of the scanning position based on a coordinate position of the template image in a measurement image. In the retinal function measuring device according to claim 6,
The at least two points on the scan line include a start point and an end point of the scan line. In the retinal function measuring device according to claim 5,
The misregistration detection means further sets at least two or more image areas separated from the scan line as a template image, and stores in advance the positional relationship between the template image and the scan line,
The retinal function measuring apparatus according to claim 1, wherein the scanning position correcting unit detects a shift of the scanning position based on the coordinate position of the template image in the measurement image and the positional relationship stored in advance. The retinal function measuring device according to claim 4,
The retinal function measuring apparatus according to claim 1, wherein the positional deviation detection means updates a search area when template matching is performed on a fundus front image based on a coordinate position of the template image detected at any time.

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