JP2011234750A - Optical coherence tomographic imaging device, and processing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technique constituted so as to acquire the tomographic image of the eyeground in a state that the visual axis of a subject is stabilized.SOLUTION: An optical coherence tomographic imaging device is constituted so as not only to perform primary scanning on the surface, which crosses the optical axis of the light applied to the eyeground at a right angle, along a predetermined direction but also to stepwise alter the start point of primary scanning along the direction crossing the predetermined direction at a right angle to irradiate the respective scanning lines in the scanning region of the eyeground with light. The optical coherence tomographic imaging device is equipped with a control means for altering the start points with respect to a plurality of the scanning lines in the scanning region at every scanning timing to set the same and executing the primary scanning along the predetermined direction from all of the set starting points within a predetermined time and a means for forming the tomographic image of the eyeground on the basis of the reflected light from the eyeground obtained by the primary scanning executed corresponding to each of the scanning timings. Here, the control means sets the start points so that the average of coordinates along the orthogonal direction in the scanning regions of all of the start points set at every scanning timing coincides with the center along the orthogonal direction in the scanning regions.

Description

  The present invention relates to an optical coherence tomography apparatus and a processing method thereof.

  As an ophthalmologic apparatus for observing an eye using an optical apparatus, for example, an anterior ocular segment photographing machine, a fundus camera, a confocal laser scanning ophthalmoscope (SLO), and the like are known. Among such devices, an optical coherence tomography (Optical Coherence Tomography: hereinafter referred to as OCT apparatus) can acquire a tomographic image of a sample (for example, retina), and thus is an indispensable apparatus for specialized retina outpatients. It is becoming.

  A B-scan (scanning in the primary direction (X / Y direction)) is performed a plurality of times in a direction (for example, Y direction) orthogonal to the B-scan direction (for example, X direction) to obtain a three-dimensional fundus image The technology to do is known. In this case, since a tomographic image of the fundus can be acquired in three dimensions, it is very effective for the spread of lesions and observation of each layer in the retina, particularly for observation of the optic nerve cell layer causing glaucoma.

  Conventionally, as a technique for acquiring a tomographic image of the fundus in three dimensions, as described in Patent Document 1, a method of sequentially acquiring B-scan images from the start point to the end point is known. In this technique, during acquisition of the image, a bright spot called a fixation lamp is placed in the field of view so that eye movement does not occur, and the viewpoint is prevented from moving.

JP 2009-42197 A

  When acquiring a three-dimensional fundus image, low-coherent light used as measurement light is generally performed using infrared light in the vicinity of 850 nm. Although the human eye does not show sensitivity to such infrared light, the human eye perceives the light as red light because it directly enters the eye. Therefore, one red bright line is visible to the human eye during the B scan.

  In the above-described conventional technique, B-scan images are sequentially acquired to form a three-dimensional fundus image. Therefore, in the human eye, the bright line moves from the start point to the end point and from the top to the bottom. Looks like. In this case, the eyeball may follow the bright line while moving as a saccade, and the line of sight (position of the eyeball) may change.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of acquiring a tomographic image of the fundus with a subject's line of sight being stabilized.

  In order to solve the above problems, according to one embodiment of the present invention, primary scanning is performed along a predetermined direction on a surface orthogonal to the optical axis of light applied to the fundus, and the orthogonal direction is orthogonal to the predetermined direction. An optical coherence tomographic imaging apparatus that irradiates each scanning line in the fundus scanning region with the light by changing the start point of the primary scanning stepwise along the scanning timing. Control means for changing and setting the starting point for a plurality of scanning lines in a scanning region, and executing the primary scanning along the predetermined direction from all of the set starting points within a predetermined time; Generating means for generating a tomographic image of the fundus oculi based on the reflected light from the fundus obtained by the primary scan executed corresponding to each scan timing, and the control means includes each scan type. The start point is set so that the average of the coordinates along the orthogonal direction in the scanning region of all the starting points set for each scanning coincides with the center along the orthogonal direction in the scanning region. And

  According to the present invention, a tomographic image of the fundus can be acquired in a state in which the subject's line of sight is stabilized.

The figure which shows an example of a structure of the optical coherence tomography apparatus (OCT apparatus) concerning one embodiment of this invention. FIG. 6 is a diagram illustrating an outline of processing when a measurement light 51 is scanned two-dimensionally with respect to the fundus (first embodiment). 3 is a flowchart illustrating an example of a processing flow in the optical coherence tomography apparatus 10 illustrated in FIG. 1. The figure which shows the outline | summary of the process at the time of making the measurement light 51 scan two-dimensionally with respect to the fundus (second embodiment).

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

(Embodiment 1)
FIG. 1 is a diagram showing an example of the configuration of an optical coherence tomography apparatus (OCT apparatus) according to an embodiment of the present invention.

  The OCT apparatus 10 is used, for example, for ophthalmic medical treatment. The OCT apparatus 10 emits low-coherent light toward the eye 30 to be examined, and acquires a three-dimensional tomographic image of the fundus (for example, the retina) based on the reflected light. Here, the OCT apparatus 10 includes a light source 11, a beam splitter 12, an XY scanner 13, a lens 14, a folding mirror 15, a driving device 16, a diffraction grating 17, a lens 18, and a one-dimensional sensor 19. The tomogram generator 20 and the controller 21 are provided.

  A low coherent light source is used as the light source 11. For example, an SLD (Super Luminescent Diode) may be used. The light source 11 only needs to emit low-coherent light, and may be, for example, ASE (Amplified Spontaneous Emission). The light emitted from the light source 11 has, for example, a wavelength of 830 nm and a bandwidth (bandwidth) of 50 nm. In the present embodiment, near infrared light is suitable for the wavelength in order to obtain a tomographic image of the human eye (for example, the retina). The wavelength and bandwidth are not limited to the above examples, and may be appropriately determined according to the measurement site to be observed.

  The beam splitter 12 branches light emitted from the light source 11 into measurement light 51 and reference light 52.

  The XY scanner 13 causes the measurement light 51 branched by the beam splitter 12 to scan two-dimensionally over a region (scanning region) 41 to be scanned on a surface 40 perpendicular to the optical axis. Although the XY scanner 13 is illustrated as a single mirror, in reality, two mirrors, an X scan mirror and a Y scan mirror, are arranged close to each other, and are located with respect to the fundus of the eye 30 to be examined. The measurement light 51 is raster-scanned on the surface 40 orthogonal to the optical axis. Note that the mirror of the XY scanner 13 is adjusted so that the center of rotation of the mirror coincides with the center of the measurement light 51.

  The XY scanner 13 B-scans (scans in the primary direction) the measurement light 51 in the X direction (predetermined direction) while tilting the measurement light 51 stepwise in the Y direction (orthogonal direction orthogonal to the X direction). That is, the XY scanner 13 scans the scanning light 41 with the measurement light 51 two-dimensionally. Thereby, a three-dimensional tomographic image of the fundus is obtained.

  The control unit 21 controls the operation of each unit in the OCT apparatus 10. The control unit 21 performs, for example, control of the light source 11, scanning control of the XY scanner 13, control of the tomographic image generation unit 20, control of driving of the driving device 16, and the like.

  Here, in order to make the description of the OCT apparatus 10 according to the present embodiment easy to understand, a flow of processing when acquiring a tomographic image of the fundus will be briefly described.

  The OCT apparatus 10 first emits light from the light source 11. The light emitted from the light source 11 enters the beam splitter 12. The beam splitter 12 branches the incident light into reference light 52 and measurement light 51. The measurement light 51 branched by the beam splitter 12 is incident on the XY scanner 13.

  The measurement light 51 incident on the XY scanner 13 is then incident on the lens 14 and is collected on the fundus (on the retina) of the eye 30 to be examined by the action of the lens 14. When the measurement light 51 is incident on the eye 30 to be examined, the return light 53 is reflected or scattered from the fundus of the eye 30 to be examined, and passes through the same optical path as the measurement light 51 to the beam splitter 12 via the lens 14 and the XY scanner 13. Incident.

  Similarly to the measurement light 51, the reference light 52 branched by the beam splitter 12 enters the folding mirror 15. The folding mirror 15 reflects the reference light 52 toward the original optical path. Thereby, the reflected light (reference light 52) enters the beam splitter 12 again through the same optical path. The folding mirror 15 is driven by the driving device 16 and is configured to be movable along the optical axis direction. Thereby, the optical path length of the reference light 52 is controlled to be substantially the same as the optical path length of the measurement light 51. Note that the driving device 16 moves the folding mirror 15 stepwise by, for example, a stepping motor.

  Here, when the return light 53 and the reference light 52 enter the beam splitter 12, these lights are combined (interference light) by the beam splitter 12. The interference light 54 obtained by this multiplexing is split by the diffraction grating 17. The spectrum of the interference light 54 by the diffraction grating 17 is performed under the same wavelength condition as the center wavelength and bandwidth of the light source.

  The interference light 54 separated by the diffraction grating 17 enters the lens 18. The light incident on the lens 18 is imaged on the one-dimensional sensor 19 by the imaging action of the lens 18. The one-dimensional sensor 19 detects the light intensity corresponding to each wavelength and generates (converts) an electrical signal. The electrical signal is sent to the tomographic image generation unit 20. The one-dimensional sensor 19 may be a CCD type or a CMOS type.

  The tomographic image generator 20 that has received the output (electric signal) from the one-dimensional sensor 19 converts each wavelength into a wave number, and then performs a Fourier transform. As a result, a tomographic image of the eye 30 to be examined (a tomographic image of the fundus) is acquired. Note that, at each position on the retina of the eye 30 to be examined, the position of the optical path length of the measurement light 51 that is equal to the optical path length of the reference light 52 is called a coherence gate. An image corresponding to the distance from the coherence gate is obtained.

  Next, an outline of processing when the measurement light 51 is two-dimensionally scanned on the fundus will be described with reference to FIG. This process is performed by the control unit 21 controlling the light source 11 and the XY scanner 13.

  FIG. 2 shows the scanning region 41 shown in FIG. The scanning region 41 indicates a region on a two-dimensional plane that is an acquisition target of a fundus tomographic image, and A1 to An and B1 to Bn are lines (scanning lines) to be scanned. W and T indicate the width of a region (scanning region) from which a fundus tomographic image is acquired. In this case, the width of scanning (B scan) in the X direction by the measurement light 51 is W, and the width of scanning in the Y direction by the measurement light 51 is L.

  The control unit 21 of the OCT apparatus 10 first divides the scanning region 41 into two along the Y direction before scanning the measurement light 51 on the fundus. Accordingly, the scanning region 41 is divided into a first region 61 and a second region 62 that are divided at equal intervals along the Y direction.

  Here, the scanning of the measuring light 51 in the primary direction (primary scanning) is alternately performed on the first region 61 and the second region 62. More specifically, A1-A1 ′, B1-B1 ′, A2-A2 ′, B2-B2′A3-A3 ′, B3-B3 ′, A4-A4 ′, B4-B4 ′,. A scanning process is performed on each scanning line in the order of An ′ and Bn−Bn ′.

  In this scanning process, the primary scanning for the first area 61 and the primary scanning for the second area 62 are performed simultaneously (strictly within a predetermined time) at each scanning timing. That is, primary scanning is performed on each region at each scanning timing. At this time, the scanning process is performed so that the average of the coordinates of the start point of the primary scanning along the Y direction between the two scanning lines always coincides with the center of all scanning regions 41 (hereinafter referred to as region center E). Is done.

  Further, the scanning processing for two scanning lines executed corresponding to each scanning timing is performed within a predetermined time. Here, the predetermined time refers to a time for the human eye to capture the bright line of the measurement light 51 as an afterimage, and the time is said to be about 30 milliseconds, for example. That is, the primary scan for the first region 61 and the primary scan for the second region 62 are performed within the time when the human eye captures the bright line of the measurement light 51 as an afterimage. Thus, the subject feels that the scanning process for two scanning lines for the first region and the second region 62 has been performed simultaneously.

  Further, at each scanning timing, the scanning process is performed so that the primary scanning start point for the first region 61 and the primary scanning start point for the second region 62 gradually move toward the region center E. . This makes it appear to the subject that the two scan lines move toward the center. Therefore, movement of the line of sight (eyeball) can be reduced.

  Here, an example of the flow of processing in the OCT apparatus 10 shown in FIG. 1 will be described using the flowchart shown in FIG. Here, an example of a processing flow when the measurement light 51 is scanned two-dimensionally on the fundus will be described.

  When this process starts, the control unit 21 of the OCT apparatus 10 first divides the scanning region 41 into two regions at equal intervals along the Y direction. That is, the image is divided into a first area 61 and a second area 62 shown in FIG. 2 (S101).

  When the region is divided, the control unit 21 of the OCT apparatus 10 sets a start point of primary scanning in the Y direction (S102 and S103). More specifically, in the first region 61 and the second region 61, a start point that is farthest from the center region E along the Y direction is selected, and that position is set as the start position of the primary scan. Set. In the case of FIG. 2, A1 is set as the start point for the first region 61, and B1 is set as the start point for the second region 62.

  When the start point of the primary scan in each area is determined in this way, the control unit 21 of the OCT apparatus 10 controls the light source 11 and the XY scanner 13 and follows the X direction from the start point set in each area. Then, the measurement light 51 is primarily scanned (S104). Thereby, a tomographic image for one scanning line is acquired from each region. That is, tomographic images for two scanning lines are acquired from the entire scanning region 41. As described above, the primary scan for the first area 61 and the primary scan for the second area 62, which are executed corresponding to each scanning timing, are performed within the time when the human eye captures the bright line as an afterimage. In the case of FIG. 2, the primary scan of the A1-A1 'line and the primary scan of the B1-B1' line are performed.

  Here, the control unit 21 of the OCT apparatus 10 determines whether or not the scanning process for all the scanning regions 41 has been completed. If the scanning process for the entire scanning region 41 has been completed (YES in S105), this process is terminated. If there is an unscanned line (NO in S105), the control unit 21 of the OCT apparatus 10 changes the position of the start point of the primary scan along the Y direction in each of the first region 61 and the second region 62. (S106). Specifically, the position of the start point for both regions is moved one step toward the region center E. In the case of FIG. 2, in the first region 61, the position of the starting point is moved by one step from the A1 to the An direction, and in the second region 62, the starting point is moved from the B1 to the Bn direction. Is moved by one step.

  Thereafter, the OCT apparatus 10 returns to the process of S104 again, and performs the scanning process for each region in the same manner as described above. As a result, the scanning process is performed on the entire scanning region 41 while the position of the start point for both regions is changed stepwise toward the region center E.

  As described above, in the present embodiment, the scanning area 41 is divided into two areas, and each divided timing is within a predetermined time (within the time that the eye perceives as an afterimage) at each scanning timing. The measurement light 51 is primarily scanned. Here, in this scanning process, the average of the coordinates along the Y direction of all the starting points of the primary scanning performed corresponding to each scanning timing is made to coincide with the area center E.

  Thereby, a tomographic image of the fundus can be acquired in a state in which the subject's line of sight is stabilized (a state in which the movement of the eyeball due to saccade or the like is suppressed).

(Embodiment 2)
Next, Embodiment 2 will be described. In the first embodiment, the case where the scanning area 41 is divided into two areas has been described as an example. However, the present invention is not limited to this. Can be processed.

  Therefore, in the second embodiment, a case where the scanning region 41 is divided into four will be described as an example of dividing the scanning region 41 into four or more even regions.

  Here, an outline of processing when the measurement light 51 is scanned in the two-dimensional direction by the XY scanner 13 will be described with reference to FIG.

  In the second embodiment, the scanning area 41 is divided into four along the Y direction. Thus, the scanning region is divided into a first region 63, a second region 64, a third region 65, and a fourth region 66 that are divided at equal intervals along the Y direction.

  Here, first, the start point of the primary scan (B scan) is set for each of the divided areas. In this case, A1, B1, C1, and D1 are set as start points. More specifically, two adjacent areas are associated as a pair, and the scanning line that is farthest along the Y direction from the boundary between the paired areas is selected as the starting point from each area, and the position Is set as the start position of the primary scan. Then, the scanning process is performed with the primary scanning from all the four start points set as one set.

  Thereafter, the measurement light 51 is scanned over the entire scanning region 41 while changing the starting point in each region at each scanning timing. That is, the starting points set for each pair of regions are changed and set so as to approach each other in a stepwise manner toward the boundary between the regions. More specifically, at the first scanning timing, primary scanning is performed with A1, B1, C1, and D1 as starting points, and at the next scanning timing, 1 is set with A2, B2, C2, and D2 as starting points. Perform the next scan. At the subsequent timing, the start point is changed and set in the same manner as described above, and at the last scan timing, the primary scan is performed with An, Bn, Cn, and Dn as the start points. Thereby, the measurement light 51 can be scanned two-dimensionally with respect to the fundus.

  Thus, also in the second embodiment, as in the first embodiment, the average of the coordinates along the Y direction at the start point of the primary scan executed at each scanning timing is along the Y direction in the entire scanning region 41. It coincides with the coordinate center position (region center E).

  The operation of the OCT apparatus 10 according to the second embodiment is different from the operation of the first embodiment in terms of detailed operation, but the overall operation (area division, setting and changing of the start point) is the same as that of the first embodiment. Since the flow is similar, the description thereof is omitted here.

  As described above, according to the second embodiment, the movement in the Y direction is less than that in the configuration of the first embodiment, and the bright lines are more dispersed. Therefore, a tomographic image of the fundus can be acquired in a state where the movement of the eyeball is suppressed.

  The above is an example of a typical embodiment of the present invention, but the present invention is not limited to the embodiment described above and shown in the drawings, and can be appropriately modified and implemented without departing from the scope of the present invention. .

  For example, in the first and second embodiments, the case where the scanning process is performed by dividing the scanning area 41 into an even number of areas and setting the start point for the divided areas has been described as an example. It is not limited to this. In the present embodiment, the average of the coordinates along the Y direction at the start point of the primary scanning executed at each scanning timing matches the center position (area center E) of the coordinates along the Y direction in all the scanning areas 41. It is only necessary to divide the area.

  In the first and second embodiments, the case where the measurement light 51 is scanned for each line in each divided region has been described as an example. However, the present invention is not limited to this, and the measurement light 51 is provided for each of a plurality of lines. You may make it scan. In this case, the effect obtained by dispersing the scanning of the measuring beam 51 is somewhat reduced, but the movement of the scanning in the Y direction is reduced, so that the time required until all scanning is completed can be shortened.

Claims (5)

The primary scanning is performed along a predetermined direction on a plane orthogonal to the optical axis of the light irradiated to the fundus, and the start point of the primary scanning is changed stepwise along the orthogonal direction orthogonal to the predetermined direction. An optical coherence tomographic imaging apparatus for irradiating each scanning line in the fundus scanning region with the light,
At each scanning timing, the starting point is changed and set for a plurality of scanning lines in the scanning region, and the primary scanning along the predetermined direction from all of the set starting points is performed within a predetermined time. Control means to be executed,
Generating means for generating a tomographic image of the fundus based on the reflected light from the fundus obtained by the primary scan executed corresponding to each scanning timing;
The control means includes
The start point is set so that the average of the coordinates along the orthogonal direction in the scanning region of all the starting points set at each scanning timing coincides with the center along the orthogonal direction in the scanning region. An optical coherence tomographic imaging apparatus. The control means includes
A dividing unit that divides the scanning region into an even number of regions at equal intervals along the orthogonal direction;
For each scanning timing, setting means for changing and setting the start point along the orthogonal direction for each of the divided regions;
Scanning control means for executing, within a predetermined time, the primary scanning along the predetermined direction from all of the start points set for each of the divided areas at each scanning timing. The optical coherence tomographic imaging apparatus according to claim 1. The dividing means includes
Dividing the scanning region into two regions at equal intervals along the orthogonal direction;
The setting means includes
At the first scanning timing, the scanning line located farthest from the center along the orthogonal direction is set as the start point in each of the divided areas, and at each subsequent scanning timing, each of the areas is set. The optical coherence tomographic imaging apparatus according to claim 2, wherein the start points set with respect to are changed and set so as to approach each other along the orthogonal direction in a stepwise manner. The dividing means includes
Dividing the scanning region into four or more even regions at equal intervals along the orthogonal direction;
The setting means includes
At the first scanning timing, all the divided areas are associated as a pair between two adjacent areas, and the scanning line that is farthest along the orthogonal direction from the boundary between the paired areas is the scanning line. Each of the paired areas is set as the start point, and in the subsequent scanning timing, the start points set for the paired areas are gradually approached toward the boundary between the areas. The optical coherence tomographic imaging apparatus according to claim 2, wherein each is changed and set. The primary scanning is performed along a predetermined direction on a plane orthogonal to the optical axis of the light irradiated to the fundus, and the start point of the primary scanning is changed stepwise along the orthogonal direction orthogonal to the predetermined direction. A processing method of an optical coherence tomography apparatus for irradiating each scanning line in the scanning region of the fundus with the light,
The control means changes and sets the starting point for a plurality of scanning lines in the scanning region at each scanning timing, and also performs the primary scanning along the predetermined direction from all of the set starting points. Executing within a predetermined time;
Generating means for generating a tomographic image of the fundus based on the reflected light from the fundus obtained by the primary scanning performed corresponding to each scanning timing;
The control means includes
The start point is set so that the average of the coordinates along the orthogonal direction in the scanning region of all the starting points set at each scanning timing coincides with the center along the orthogonal direction in the scanning region. A processing method for an optical coherence tomographic imaging apparatus.

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