JP6806481B2 - Imaging device, control method of imaging device, and program - Google Patents

Description

The present invention relates to a photographing device that captures an image of an eye to be inspected, a control method of the photographing device , and a program .

Currently, various ophthalmologic imaging devices are used in which measurement light is scanned on an eye to be inspected and observation and imaging are performed using the reflected light of the scanning light from the eye to be inspected. Examples of these ophthalmic instruments include an optical coherence tomography (OCT), a cofocal laser scanning ophthalmoscope (SLO), an AO-SLO (Adaptive Optics), and the like. In these devices, a technique of scanning the measurement light on the eye to be inspected using a galvano scanner, a resonance type scanner, a polygon scanner, or the like and continuously acquiring data at a plurality of points of the eye to be inspected is used. ..

When using this technique, it is necessary to accurately detect the scanning speed and scanning position of the measurement light in the ophthalmic apparatus on the eye to be inspected in order to correctly observe or photograph the desired part of the eye to be inspected. However, it is known that the scanners used in these ophthalmologic imaging devices change their scanning speeds and scanning positions due to various factors such as individual differences and changes in ambient temperature.

As a solution to this problem, a correction chart is attached at a position conjugate with the light receiving element, and the image obtained by photographing this correction chart is compared with the fundus image to obtain a signal from the reflected light. A technique for correcting timing is known. (Patent Document 1) Further, there is known a technique for correcting the sampling timing based on a position signal obtained from a driving unit of a resonance type scanner. (Patent Document 2)

Japanese Unexamined Patent Publication No. 2014-68704 Japanese Unexamined Patent Publication No. 2014-68703

However, Patent Document 1 does not disclose a specific position where the correction chart is arranged, and when the correction chart is attached within the optical axis of the photographing optical system, the correction data is updated at the time of updating. It is necessary to attach a correction chart each time. In this case, there is a problem that it takes time to update the correction data. In particular, if the scanning speed or scanning position changes during the examination of the eye to be examined and the correction data is updated to identify the cause, it may be difficult for the user to attach the correction chart during the examination. There are many.

Further, the method using the position signal obtained from the drive unit of the resonance type scanner exemplified in Patent Document 2 cannot be applied to a scanner that cannot acquire the position signal. Further, since the position signal indicates the position of the scanner alone, if the position of the entire scanner unit in the ophthalmologic imaging apparatus is displaced, it cannot be corrected. That is, it is not possible to accurately correct the scanning speed and scanning position of the measurement light as an ophthalmologic imaging device.

In view of the above circumstances, the present invention provides an imaging apparatus and a control method thereof that can accurately correct changes in the scanning speed and scanning position of the measurement light on an object to be inspected in a short time. With the goal.

In order to solve the above problems, the imaging device according to one aspect of the present invention is
Luminous flux projection means that projects luminous flux onto the object to be inspected,
An image signal acquisition means for acquiring an image signal based on the reflected light of the luminous flux from the object to be inspected, and
A scanning means included in the luminous flux projection means and scanning the luminous flux on the object to be inspected.
An image generation means that generates an image based on the acquired image signal, and
A position information generating means arranged outside the optical path when the luminous flux projecting means projects the luminous flux onto the object to be inspected.
A control means for causing the scanning means to scan the position information generating means with the luminous flux, and
Based on the position information obtained from the scanned luminous flux in the position information generating means,
A correction means for correcting the timing of acquiring the image signal by the image signal acquisition means, and
Equipped with a,
The correction of the timing of acquiring the image signal by the correction means is continuously in the scanning of the object to be inspected of the light beam by said scanning means for obtaining said image signal is performed, characterized in Rukoto.

According to the present invention, it is possible to accurately correct changes in the scanning speed and scanning position of the measurement light on the object to be inspected in the ophthalmologic imaging apparatus in a short time.

It is the schematic which shows the structure of the whole ophthalmic apparatus which concerns on one Embodiment of this invention. It is explanatory drawing of the optical system in the ophthalmic apparatus shown in FIG. It is explanatory drawing about the SLO image obtained by an ophthalmic apparatus and the operation of a resonance type scanner. It is explanatory drawing of the chart for scanning correction in Embodiment 1 of this invention. It is a flowchart which shows the photographing procedure at the time of obtaining the SLO image in one Embodiment of this invention. It is explanatory drawing of the scanning correction method in Embodiment 1 of this invention. It is explanatory drawing of the photodetector in Embodiment 2 of this invention. It is explanatory drawing of the scanning correction method in Embodiment 2 of this invention. It is explanatory drawing of the photodetector in Embodiment 3 of this invention. It is explanatory drawing of the scanning correction method in Embodiment 3 of this invention.

Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. It should be noted that the following embodiments do not limit the present invention relating to the scope of claims, and not all combinations of features described in the present embodiment are essential for the means for solving the present invention. Absent.

Further, in the present embodiment, a confocal laser scanning ophthalmoscope (SLO device) is given as an example as an ophthalmologic imaging device, but the device is not limited to the SLO device, and an OCT device, an AO-SLO device, or the like may be used as an eye subject. It is generally applicable to scanning ophthalmologic imaging devices.

[Embodiment 1 of the present invention]
Hereinafter, as an embodiment of the present invention, a case where the present invention is applied to an SLO apparatus will be described.

(Outline configuration of the device)
FIG. 1 shows a schematic configuration of an SLO apparatus according to this embodiment.
The SLO device 200 shown in FIG. 1 includes an optical head 900, a stage unit 950, a base unit 951, a chin rest 323, a control unit 925, a storage unit 926, a display unit 928, and an input unit 929. The optical head 900 is a measurement optical system for capturing a two-dimensional image of the fundus of the eye to be inspected. The stage unit 950 functions as a moving unit in which the optical head 900 can be moved in the xyz direction in the drawing by using a motor (not shown). The base portion 951 supports the stage portion 950, and incorporates a power supply, a part of the optical system, and the like. The chin rest 323 is fixed to the base portion 951, and by fixing the chin and the forehead of the subject, the fixation of the eye of the subject (eye to be examined) is promoted.

The control unit 925 is a personal computer that also serves as a control unit for the optical tomography imaging device, and controls the SLO device and configures the fundus image. The storage unit 926 is composed of a hard disk that stores a program for image fundus imaging and the like, and is built in the control unit 925. The display unit 928 is a monitor, and the input unit 929 gives an instruction to a personal computer, and specifically includes a keyboard and a mouse. In the present embodiment, the control unit (personal computer), the hard disk, the display unit, and the input unit are provided outside the SLO device 200 main body, but it is also possible to have a configuration built in the SLO device 200 main body. ..

(Structure of shooting optical system)
The configuration of the imaging optical system of the ophthalmologic imaging apparatus according to the present embodiment will be described next with reference to FIG.
First, the inside of 900 parts of the optical head will be described. Inside the optical head 900, the objective lens 101-1 is arranged so as to face the eye 100 to be inspected. The first dichroic mirror 102 is arranged on the optical axis of the objective lens 101-1. The optical path leading to the eye 100 to be inspected is branched by the first dichroic mirror 102 into an optical path L1 of the anterior segment observation system and an optical path L2 of the internal fixation lamp and the SLO optical system for each wavelength band.

The optical path L1 has a configuration in which the CCD 123 for observing the fundus of the eye receives the reflected light from the fundus, and the lens 120 and the lens 121 are arranged on the optical axis thereof. The CCD 123 has sensitivity in the wavelength of the illumination light for front eye observation (not shown), specifically, in the vicinity of the wavelength of 970 nm.

A second dichroic mirror 106 is further arranged on the optical axis of the optical path L2. The optical path L2 branches the reflected light from the fundus of the eye 100 to be examined into the optical path L3 of the internal fixation lamp optical system and the optical path L4 of the SLO optical system by the second dichroic mirror 106. A lens 101-2, a galvano scanner 104, a resonance type scanner 103, and a lens 105 are arranged in this order on the optical path L2 from the first dichroic mirror 102, and reach the second dichroic mirror 106.

An SLO focusing lens 107, a perforated mirror 108, an SLO light source 109, and a photodetector 110 are arranged on the optical axis of the SLO optical system in the transmission direction of the second dichroic mirror 106. The photodetector 110 constitutes a light receiving means for receiving the reflected light from the eye 100 to be examined in the present embodiment. Further, the fixation focusing lens 111 and the internal fixation lamp 112 are arranged on the optical axis of the internal fixation lamp optical system in the reflection direction of the second dichroic mirror 106. Further, the photodetector 110 is connected to an A / D converter (not shown). Further, the A / D converter is connected to an FPGA (not shown). The photodetector 110 outputs a signal according to the received light, and the A / D converter converts the output of the photodetector 110 into a digital signal. The FPGA samples the output of the A / D converter at a predetermined sampling interval, and outputs the sampled digital signal to the control unit 925. The control unit 925 controls the generation and display of the image of the eye to be inspected based on the output from the FPGA. In the present embodiment, the method of correcting the sampling interval performed by the FPGA will be described, but the sampling interval (A / D conversion interval) of the A / D converter may be changed. The control unit 925 may perform sampling at predetermined sampling intervals. Further, the FPGA may be included in the control unit 925.

The SLO light source 109 emits measurement light having a center value in the vicinity of a wavelength of 780 nm, and the photodetector 110 has sensitivity in the vicinity of a wavelength of 780 nm as received light. On the other hand, the internal fixation lamp 112 generates visible light to promote fixation of the subject.
The luminous flux emitted from the SLO light source 109 or the internal fixation lamp 112 is once imaged in the vicinity of the first dichroic mirror 102, and is imaged again in the vicinity of the fundus of the eye 100 to be inspected. The SLO focusing lens 107 and the fixation focusing lens 111 are driven on the optical axis by a motor (not shown) so that the second imaging position coincides with the fundus of the eye 100 to be inspected. That is, by driving these focusing lenses, the first imaging position also changes in the vicinity of the first dichroic mirror 102.

The imaging position of the luminous flux on the fundus is changed by the resonance type scanner 103 that drives the luminous flux in the X direction and the galvano scanner 104 that drives the luminous flux in the Y direction. With these scanners, the luminous flux is scanned in two dimensions on the fundus. This luminous flux is scattered on the fundus, and the reflected light scattered in the direction of the optical path L2 is reflected by the perforated mirror 108 and detected by the photodetector 110. The photodetector 110 is, for example, a photodiode, and constitutes the image signal acquisition means in the present embodiment. The luminous flux and resonance type scanner 103 emitted from the SLO light source 109 described here constitute a scanning means for scanning the measurement light and the measurement light, respectively, in the present embodiment. Further, the photodetector 110 constitutes a first acquisition means for acquiring an image signal based on the return light of the measurement light from the eye 100 to be inspected, and the acquisition of the image signal is executed by the first acquisition step.

An SLO image can be obtained by processing the signal obtained by the photodetector 110 by the method described later. In this way, the SLO device 200 can image the entire region of interest in the fundus of the eye to be inspected. The configuration from the eye 100 to be examined to the SLO optical system and the SLO optical system described above constitute a luminous flux projection means for projecting a luminous flux onto the eye 100 to be inspected in the present embodiment. Further, the resonance type scanner 103 and the galvano scanner 104 are included in the light flux projection means in the present embodiment to form a scanning means for scanning the light flux on the eye to be inspected.

Further, the internal fixation lamp 112 projects various patterns such as a cross shape and an X shape onto various positions of the fundus of the eye to be inspected by controlling the lighting in conjunction with scanning by the resonance type scanner 103 and the galvano scanner 104. Is possible. As a result, the eye to be inspected can be directed in various directions, and a wide area in the fundus of the eye to be inspected can be photographed.

The chart 130 arranged at a position deviated from the optical axis of the optical path L2 is a scanning correction chart described later. As shown in FIG. 2, the scanning correction chart 130 is arranged outside the optical axis of the optical path L2. In the example shown in FIG. 2, the scanning correction chart 130 is arranged parallel to the optical axis of the optical path L2, but is not limited to this, and is arranged at an angle with respect to the optical axis of the optical path L2. You may do it. For example, the scanning correction chart 130 may be arranged so as to be perpendicular to the optical axis of the optical path L2, or may be arranged at an angle with respect to the optical axis of the optical path L2.

(Generation of SLO image)
Next, the SLO image will be described with reference to FIG.
The signal level obtained by the photodetector 110 is converted into the brightness of each pixel to generate an SLO image. The actual generation of the SLO image is executed by a module that functions as an image generation means in the control unit 925. Specifically, the pixels obtained while the resonant scanner 103 scans the light beam once in the X direction on the fundus are arranged in the horizontal direction to obtain one-line data. By arranging the one-line data obtained by repeating this process vertically, a two-dimensional image as shown in FIG. 3A is obtained. Since the resonance type scanner 103 is reciprocated, the scanning directions are opposite between the odd-numbered scan and the even-numbered scan. Therefore, in FIG. 3A, the odd-numbered line data and the even-numbered line data are arranged in reverse to obtain a two-dimensional image having a unified direction.

FIG. 3B shows the driving of the resonance type scanner 103. The horizontal axis represents the time, and the vertical axis represents the deflection angle of the resonance type scanner 103. The pixels on the dotted line 301 in FIG. 3A are created from the signals at time 311 or 321 in FIG. 3B. Similarly, the pixels on the dotted lines 302, 303, and 304 were created from the signals at time 312 or 322, time 313 or 323, and time 314 or 324, respectively. Here, the times 311, 312, 313, and 314 are at equal time intervals. The times 321 and 322, 323, and 324 are at equal time intervals. The deflection angles of the resonance type scanner 103 at that time are 331, 332, 333, and 334, respectively.

Since the drive of the resonant scanner is not constant velocity, the intervals of the angles 331, 332, 333, and 334 at each time are different. Therefore, the dotted lines 301, 302, 303, and 304 in FIG. 3A are not actually equidistant on the fundus, but are displayed at equidistant on the image. That is, the SLO image of FIG. 3A has distortion. Therefore, it is necessary to correct the signal acquisition interval by the photodetector 110 by the method described later.

(Explanation of scanning correction chart)
The scanning correction chart 130 will be described with reference to FIG.
FIG. 4A shows a portion related to the scanning correction chart 130 of FIG. The galvano scanner 104 changes the angle of the mirror portion at the time of correction, and projects a luminous flux onto, for example, a scanning correction chart 130 arranged off the optical axis along the optical path 401. By changing the angle of the mirror portion of the galvano scanner 104, the luminous flux can be guided along different optical paths such as the optical path 402 and the optical path 403, and the luminous flux can be projected to an arbitrary position on the scanning correction chart 130. The scanning correction chart 130 is arranged near the first dichroic mirror 102, that is, at a position where a luminous flux is formed. Therefore, the luminous flux emitted from the SLO light source 109 is in focus at any position on the scanning correction chart 130. The imaging position of the luminous flux is determined by the position on the optical axis of the SLO focusing lens 107. Therefore, by controlling the angle of the galvano scanner 104 according to the position of the SLO focusing lens 107, the luminous flux can be focused on the scanning correction chart 130. In other words, the luminous flux can be focused by the correction light focusing means including the SLO focusing lens 107 and the galvano scanner 104, which is outside the scanning range of the luminous flux when scanning the luminous flux on the fundus of the eye to be inspected. The scanning correction chart 130 is arranged at such a position. Further, the position is a predetermined range around the position where the light beam is formed between the resonance type scanner 103 and the eye examination position when the light beam is formed on the examination position of the eye to be inspected, and the correction light is used. It can also be defined as a range in which the imaging position can be adjusted by the focusing means.

FIG. 4B is a diagram showing a chart surface of the scanning correction chart 130. FIG. 4A shows a case where the scanning correction chart 130 is viewed from the direction of the first dichroic mirror 102. On the chart surface of the scanning correction chart 130, a plurality of parallel lines having low reflectance are drawn on a perfect diffusion surface having high reflectance in parallel with the scanning direction of the galvano scanner 104. Further, in the present embodiment, the central line is drawn thicker than the other lines.

Here, the luminous flux is projected at a position corresponding to the angle between the resonance type scanner 103 and the galvano scanner 104. For example, if the galvano scanner 104 projects a luminous flux onto the optical path 403, the luminous flux is projected at any position on the scanning line 410. The position of the scanning line 410 to be projected is determined according to the angle of the resonant scanner 103. In particular, when the angle of the resonant scanner 103 is the center, the luminous flux is projected on the point where the scanning line 410 and the thick line in the center of the scanning correction chart 130 intersect. By driving the resonance type scanner 103 in this state, the luminous flux can be scanned on the scanning correction chart 130 along the scanning line 410. Each of the parallel lines of the scanning correction chart 130 is drawn at a position corresponding to an evenly spaced angle of the resonant scanner 103.

FIG. 4C is a graph showing the signal intensities obtained by scanning the luminous flux on the scanning correction chart 130 described above. In the figure, the horizontal axis is time and the vertical axis is signal strength. Since the reflectance is low on the parallel lines of the scanning correction chart 130, the signal intensity is low while scanning on the lines. By binarizing the signal strength data with a threshold value of 420, it is possible to distinguish between the time of scanning on the line and the time of not scanning. Further, as described above, in the present embodiment, the central line in the parallel line is drawn thicker than the other lines. As a result, the time of low signal intensity obtained when the luminous flux is scanned on the center line becomes longer than that of the other lines, and a reference of the position on the scanning correction chart 130 in which the luminous flux is scanned can be obtained. In the present embodiment, the thickness of the line is changed, but the present invention is not limited to this as long as a signal change mode different from that of other lines can be obtained by changing the interval, changing the reflectance, or the like.

In the scanning correction chart 130 described above, the diffusion surface and the regions arranged in parallel on the surface having a reflectance different from the reflectance of the diffusion surface are arranged according to a predetermined rule. Any component on the chart to be created may be used. In the present embodiment, the regions arranged in parallel are composed of linear regions, and the extending direction thereof is parallel to one direction when the scanning means scans the luminous flux in two directions of X and Y. Is placed in. More specifically, it is preferable that the linear region is arranged parallel to the scanning direction by the galvano scanner 104. That is, it is preferable that the linear region is arranged perpendicular to the scanning direction by the resonant scanner 103. Further, as shown in FIG. 2 in the present embodiment, the chart-like structure is preferably arranged outside the optical path when the luminous flux projection means projects the luminous flux onto the eye to be inspected. Further, it is preferable that the scanning correction chart 130 is arranged between the objective lens 101-1 and the resonance type scanner 103. That is, the scanning correction chart 130 may be a member having a pattern arranged in a range where the measurement light by the resonance type scanner 103 can be irradiated and outside the scanning range of the measurement light with respect to the eye to be inspected. ..

(SLO shooting flow)
FIG. 5 shows the flow of SLO shooting. First, the control unit 925 starts driving the resonance type scanner 103 in step S501. Next, the control unit 925 turns on the SLO light source 109 in step S502. Next, in step S503, the control unit 925 obtains the angle of the galvano scanner 104 corresponding to the position on the optical axis of the SLO focusing lens 107. The corresponding angle is the angle at which the luminous flux is focused on the scanning correction chart 130 in the current state of the SLO device 200, and is calculated by the control unit 925 by calculation based on the optical system. The angle may be calculated based on a table held in advance instead of calculation.

Next, the control unit 925 drives the galvano scanner 104 to the angle obtained by the above method in step S504. After the drive of the galvano scanner 104 is completed, the luminous flux is scanned on the scan correction chart 130 by the resonance type scanner 103 in step S505. The control unit 925 functions as a control means for causing the resonance type scanner 103, which is a scanning means, to scan the scanning correction chart 130 with the luminous flux. At this time, the signal acquisition (sampling) by the FPGA is set to an equal time interval of a predetermined interval. By reciprocating the resonance type scanner 103 in this way, two 1-line data can be obtained. That is, the measurement light is scanned a plurality of times on the scanning correction chart 130. When the resonance type scanner 103 scans the luminous flux on the scanning correction chart 130, so-called position information regarding the scanning position can be obtained. That is, the control unit 925 causes the resonance type scanner 103 to perform a plurality of scans including a reciprocating scan so that a plurality of position information (information indicating the operation of the scanning means) can be obtained. The line data to be acquired may be two or more.

Next, the control unit 925 corrects the sampling interval by FPGA by the correction method described later in step S506. Next, the control unit 925 drives the galvano scanner 104 toward the fundus in step S507. Next, in step S508, the control unit 925 performs a two-dimensional scanning of the luminous flux by the resonance type scanner 103 and the galvano scanner 104 on the fundus. It is preferable that the scanning of the measurement light for acquiring the image information, the scanning of the measurement light for acquiring the data for correction, and the correction of the sampling interval are continuously performed. At this time, the signal acquisition by the photodetector 110 is performed at the interval corrected by step S506.

That is, the image is generated by the information obtained by the scanning position of the luminous flux by both scanners or the reflected light associated with the scanning position corresponding to the angular position of the scanners. At that time, the image generation method by the image generation means is corrected based on the information obtained by scanning the luminous flux on the scanning correction chart 130. More specifically, the timing when the above-mentioned FPGA samples the output of the photodetector 110 is corrected. That is, the timing of acquiring this image information when acquiring the image signal based on the reflected light from the eye 100 to be inspected is corrected, and the acquisition timing is determined. The correction or determination of the acquisition timing is executed by the module functioning as the correction means or the determination means in the control unit 925. By this correction, the sampling timing that was at equal time intervals is modulated to non-equal time intervals, and the positions where the light flux is reflected on the eye 100 to be inspected for acquiring the image signal are set at equal intervals.

In this way, the control unit 925 generates an SLO image in step S509 and displays it on the display unit 928. The control unit 925 determines in step S510 whether or not the shooting preparation is completed. If there is an input from the input unit 929 to press the shooting button, the control unit 925 determines that the shooting preparation is completed. The judgment criteria may be other criteria. For example, the in-focus state may be determined from the brightness of the SLO image, and the in-focus state may be determined to be ready for shooting. In contrast to the above-mentioned first acquisition step, the step of acquiring information indicating the operation of the resonance type scanner 103 based on the output obtained from the scanning correction chart 130 is the second acquisition step. Further, a configuration for acquiring information indicating the operation of the resonance type scanner 103 from the scanning correction chart 130 or the like constitutes a second acquisition means.

When it is determined that the shooting preparation is completed, the control unit 925 saves the SLO image in the storage unit 926 in step S511 and displays it on the display unit 928. Finally, the control unit 925 turns off the SLO light source 109 in step S512, and ends the shooting.

If it is determined that the shooting preparation is not completed, the control unit 925 returns to step S503 and repeats the above-described processing. While repeating the above-mentioned process, the operator can drive the SLO focusing lens 107 by the input from the input unit 929 to focus the luminous flux on the fundus. Further, the control unit 925 may periodically determine the focusing state by the above-mentioned method, and drive the SLO focusing lens 107 so that the light flux is focused on the fundus.

By continuously executing the correction and the image acquisition in this way, the control unit 925 can correct the sampling interval each time one SLO image is acquired. Therefore, even if the scanning time of the resonant scanner 103 changes with the passage of time, the sampling interval can be corrected immediately. The control unit 925 does not correct the sampling interval every time one SLO image is acquired, but every time N (N is 2 or more) SLO images are acquired, that is, after scanning the measurement light with respect to the eye to be inspected. The sampling interval may be corrected. That is, the step of acquiring the image signal of the SLO image, the step of acquiring the information indicating the operation of the resonant scanner 103, and the step of determining the acquisition timing of the image signal based on the information indicating the operation are repeatedly executed. It may be that.

The above is the flow of SLO shooting. The timing of correction may be another control method. For example, the correction may be performed every time a predetermined time elapses, or the correction may be performed at the start of the inspection. If the change in the resonant scanner is large, correction may be performed during image acquisition. They can also be switched by the drive control of the galvano scanner.

(Explanation of scanning correction)
Next, the scanning correction method will be described with reference to FIG. The scanning correction is performed on the outward path and the return path of the reciprocating operation of the resonance type scanner 103. Since the operation directions of the outward route and the return route are only reversed, only the correction of the outward route will be described below.

The signal strength data obtained from the scanning correction chart 130 obtained in step S505, for example, the data shown in FIG. 4C, is binarized at a threshold value of 420 to calculate the center of gravity. As a result, the detection times t1, t2, and t3 are obtained for each line. The description of the fourth and subsequent lines will be omitted. The angle of the resonant scanner 103 corresponding to each line of the scanning correction chart 130 is stored in advance in the storage unit 926, from which the resonant scanner angles x1, x2, and x3 at times t1, t2, and t3 are obtained. .. Coordinates of these points (t1, x1), (t2, x2), (t3, x3), and all the points obtained in the same manner, where the horizontal axis is the time t and the vertical axis is the angle x of the resonance type scanner 103. When plotted in, a graph as shown in FIG. 6 is obtained. The angle x of the resonance type scanner 103 is represented by, for example, a coordinate system in which the optical axis of the resonance type scanner is 0. For example, the angle at the center of the angle range that changes when the resonant scanner 103 acquires an SLO image is set to 0.

ここで、Ａは振幅、即ち共振型スキャナ１０３の最大振り角である。ωは角周波数（＝２π／Ｔ）、αは初期位相、即ち共振型スキャナの同期信号を検出した時刻の位相である。この式（１）は、次の式（２）の形に変形できる。

ただし、

である。 Further, since the resonance type scanner 103 outputs a synchronization signal for each cycle, the control unit 925 can calculate the period of the resonance type scanner 103 by detecting the synchronization signal. Let this cycle be T.
Then, all the above data can be approximated by the following equation (1).

Here, A is the amplitude, that is, the maximum swing angle of the resonance type scanner 103. ω is the angular frequency (= 2π / T), and α is the initial phase, that is, the phase at the time when the synchronization signal of the resonant scanner is detected. This equation (1) can be transformed into the form of the following equation (2).

However,

Is.

The a and b of the formula (2) are the above data (t1, x1), (t2, x2) ,. .. .. It can be obtained from the method of least squares. From there, A and α can be obtained by equation (3).

で得られる座標で信号取得を行えばよい。ｉは画素番号、即ち１からｎの範囲の整数である。 Let n be the number of pixels in the SLO image, and let X1 to Xn be the angles of the resonant scanner corresponding to the observation range on the fundus. In order to acquire signals on the fundus at equal intervals, the following equation (4)

The signal may be acquired with the coordinates obtained in. i is a pixel number, that is, an integer in the range of 1 to n.

Therefore, by substituting X1, X2, X3, ..., Xn into the inverse function of the equation (1), the time to acquire the signal, T1, T2, ..., Tn is obtained. The T1, T2, ..., Tn are stored in the storage unit 926 as the corrected signal acquisition time. In step S508, by acquiring the signal at this time, it is possible to obtain an SLO image having no distortion or less distortion.

The above is the correction method of the signal acquisition interval when scanning the luminous flux and acquiring the signal. In this correction method, it is possible not only to correct the drive of the resonance type scanner alone, but also to correct the entire SLO optical system including the change in the positional relationship between the SLO light source, the resonance type scanner, and each mirror. Therefore, the scanning position of the SLO apparatus can be accurately corrected.

The arrangement (position or angle) of the scanning correction chart 130 may be different from the example shown in FIG. 4 and the like. The chart may be shortened and the angle of the galvano scanner during correction may be controlled by a predetermined fixed angle. In that case, since the luminous flux does not focus on the chart depending on the position of the SLO focusing lens 107, it may be controlled to drive the SLO focusing lens 107 to a fixed position at the time of correction. Alternatively, the position of the line on the chart may be detected by acquiring the signal in the out-of-focus state and obtaining the center of gravity of the portion having low signal strength.

Further, in the present embodiment, the time T1 ,. .. .. , Tn is obtained in advance, and then the signal is acquired, but the signal may be acquired first. For example, a signal is acquired in advance at all available times, the acquired signal level is stored, and T1 ,. .. .. , The data corresponding to Tn may be selected.

As described above, the chart-like structure exemplified in the scanning correction chart in the above-described embodiment is used to obtain position information related to the scanning position when the light flux is scanned by the scanner. Therefore, these configurations are defined as the position information generating means in the present invention.

[Embodiment 2 of the present invention]
In the present embodiment, a photodetector is used as a light receiving element instead of the scanning correction chart as the position information generating means, and the signal acquisition time is corrected based on the time when the light flux is received by the photodetector.

(Device configuration)
FIG. 7 is a diagram showing the arrangement of the photodetectors of the present embodiment. The configuration of the apparatus of this embodiment is the same as that of the first embodiment except for the parts shown in FIG. 7.

The photodetector 131 has a sensitivity characteristic near the wavelength of the light emitted from the SLO light source 109, and is arranged at a position close to the position where the scanning correction chart 130 is arranged in the first embodiment. FIG. 7A is a diagram in which the photodetector 131 and related configurations are observed from the same angle as in FIG. 4A of the first embodiment. The photodetector 131 is arranged outside the optical path when the luminous flux projection means projects the luminous flux onto the eye to be inspected.

Further, the photodetector 131 is arranged at a position away from the center of the scanning range of the luminous flux by the resonant scanner 103 in the driving direction of the resonant scanner 103, that is, the X-axis. FIG. 7B is a diagram in which the arrangement of the photodetector 131 is observed from an angle different from that in FIG. 7A. The reason why the position of the photodetector 131 is not the center of the above-mentioned luminous flux scanning range on the X-axis will be described later.

When the resonant scanner scans the sensor surface of the photodetector 131, the photodetector 131 detects the light from the SLO light source and outputs an analog signal. This analog signal is binarized by a comparator at a certain threshold value and input to the control unit 925 as a pulse-shaped digital signal. The time at the center of the pulse at this time is defined as the detection time. The detection time may have other definitions. For example, in order to suppress the influence of noise of the analog signal, a rising threshold value and a falling threshold value of the pulse signal may be provided separately. Further, the center of gravity of the analog signal may be obtained and used as the detection time. In addition, the detection time may be defined by using a special calculation formula according to the output characteristics of the photodetector and the drive characteristics of the resonance type scanner.

(Explanation of scanning correction)
In the scanning correction of the present embodiment, the operation of the resonance type scanner is estimated by using the equation (1) of the first embodiment by a method different from that of the first embodiment. The estimation method will be described with reference to FIG.

が得られる。
その後は実施形態１と同様に、信号取得すべき座標Ｘ１、Ｘ２、Ｘ３,．．．を式（４）によって求め、それを式（１）に代入することによって、信号取得すべき時刻Ｔ１、Ｔ２、…、Ｔｎを得ることができる。 FIG. 8A is a diagram showing the timing of driving the resonant scanner and detecting by the photodetector in the present embodiment. When the resonant scanner makes one round trip, the photodetector 131 detects the light from the SLO light source once each on the outward path and the return path. The detection time of the outward route is t1, the detection time of the return route is t2, and the angle of the resonance type scanner when scanning the photodetector is x1. x1 is a constant determined when adjusting the device.
A and α of the equation (1) can be obtained by solving two equations in which (t1, x1) and (t2, x1) are substituted for (t, x) of the equation (1). In particular,

Is obtained.
After that, as in the first embodiment, the coordinates X1, X2, X3 ,. .. .. By the equation (4) and substituting it into the equation (1), the times T1, T2, ..., Tn to be signal-acquired can be obtained.

FIG. 8B is a diagram showing a case where the photodetector is arranged at the center of the scanning range in the X-axis direction, unlike the present embodiment. In this case, the amplitude of the resonant scanner, that is, A in the equation (1) cannot be obtained. This will be explained. As can be seen from FIG. 8B, when x1 is the center, that is, 0, the time from the detection time t1 to t2 is exactly half of the period T, that is, T / 2 (= π / ω). Therefore, when t2-t1 = π / ω and x1 = 0 are substituted into the equation (6), A = −0 / 0, and A cannot be obtained. Therefore, the photodetector 131 needs to be arranged at a position away from the center in the X-axis direction. On the other hand, since the speed change of the resonance type scanner becomes large at a position far from the center, the detection accuracy, that is, the accuracy of the detection time of the pulse center may deteriorate. Further, depending on the position, the amplitude of the resonance type scanner may be insufficient to scan the photodetector 131. Therefore, it is desirable to arrange the photodetector 131 near a position of about half of the maximum amplitude of the resonance type scanner. That is, it is desirable that the photodetector 131, which is the light receiving means, is arranged at a position separated from the scanning center when the resonance type scanner 103, which is the scanning means, scans the luminous flux.

Further, in the present embodiment, the period of the resonance type scanner is calculated from the synchronization signal of the resonance type scanner, but other methods may be used. For example, it may be calculated based on the detection time by the sensor. At that time, in consideration of the possibility that the speeds may differ between the outward path and the return path of the reciprocating drive of the resonance type scanner, the cycles obtained at different times may be used separately for the outward path and the return path.

[Embodiment 3 of the present invention]
This embodiment is an embodiment in which two photo detectors are arranged to further improve the accuracy of scanning correction. In the present embodiment, even when the optical axis of the resonance type scanner is deviated due to a change in the environment or the like, scanning correction can be performed in consideration of the deviation.

(Device configuration)
FIG. 9 is a diagram showing the arrangement of the photodetectors of the present embodiment. The configuration of the device of the present embodiment is the same as that of the second embodiment except that two photo detectors are arranged.

FIG. 9A is a diagram in which the photodetector is observed from the same angle as in FIGS. 4A and 7A. The photodetector 131 is the same as the photodetector of the second embodiment, and is arranged in the same place as the second embodiment. The photodetector 132 is a photodetector having the same structure as the photodetector 131. As shown in FIG. 9A, the photodetector 132 is arranged at a position overlapping the photodetector 131 in the XZ plane. Further, FIG. 9B shows a state observed in the YZ plane from different angles. As shown in the figure, the photodetector 132 is arranged at a position substantially symmetrical with the photodetector 131 with respect to the Y axis, that is, at a position where the luminous flux can be received when the deflection angle of the resonance scanner is the same on the opposite side of the photodetector 131. ing.

式（７）は、式（１）に定数項Ｂが追加されたものである。Ｂは共振スキャナの光軸と装置の光軸のずれ量である。共振型スキャナが１往復したときに、ｘ１の位置に配置されたフォトディテクタ１３１による検出時刻をｔ１及びｔ２とする。ｘ１’の位置に配置されたフォトディテクタ１３２による検出時刻をｔ１’及びｔ２’とする。ｘ１及びｘ１’は装置の調整時に決まる定数である。 (Explanation of scanning correction)
The scanning correction of this embodiment will be described with reference to FIG. In this embodiment, the following formula is used instead of the formula (1) of the first and second embodiments.

Equation (7) is an addition of the constant term B to equation (1). B is the amount of deviation between the optical axis of the resonance scanner and the optical axis of the device. When the resonance type scanner makes one reciprocation, the detection times by the photodetector 131 arranged at the position of x1 are t1 and t2. Let t1'and t2' be the detection times by the photodetector 132 arranged at the position of x1'. x1 and x1'are constants determined when adjusting the device.

ただし、

である。 When the four equations obtained by substituting (t1, x1), (t2, x1), (t1', x1'), and (t2', x1') into the equation (7) are solved, the equation (7) A, B, α can be obtained.

However,

Is.

After that, as in the first and second embodiments, the coordinates X1, X2, X3 ,. .. .. Is obtained by the equation (4), and by substituting it into the equation (7), the times T1, T2, ..., Tn to be signal-acquired can be obtained.

Focusing on equation (10), when the difference between ψ and ψ'and the difference between x1 and x1'are small, the denominator and numerator on the right side of equation (10) are both small values, and the calculation accuracy of B is correct. Get worse. That is, it is desirable that ψ and ψ'and x1 and x1'are values that are separated to some extent. This means that it is desirable that the two photodetectors are separated from each other. Therefore, in the present embodiment, the photodetector 131 and the photodetector 132 are arranged at positions substantially symmetrical with respect to the Y axis. However, other arrangements may be used as long as A, α, and B in the equation (7) can be obtained with sufficient accuracy.

Further, the position of the photodetector in FIG. 9A may be different from that of the present embodiment. For example, the position may overlap with the optical axis of FIG. 9A. Even if the angle between the photodetector and the optical axis is small in FIG. 9 (a), if the photo detector is far from the optical axis in FIG. 9 (b), the image can be taken without hindering the scanning of the eye to be inspected. Can be done.

Further, the two photodetectors do not have to overlap in the XZ plane as shown in FIG. 9A. If the angles of the two photodetectors are different, all the information in FIG. 10 can be obtained by pointing the galvano scanner at each angle in turn.

Further, three or more photo detectors may be arranged. Equations (1) and (7) are based on the premise that the drive of the resonant scanner is expressed by a trigonometric function, but a term that corrects the deviation between the trigonometric function and the actual drive may be added. Further, a special function may be used according to the actual drive of the resonance type scanner.

(Other embodiments)
The position information generating means in the present invention is not limited to the scanning correction chart and the photodetector. For example, a mirror may be used, or a line sensor or an area sensor may be used. Further, the scanning means for acquiring the position by the position information generating means is not limited to the resonance type scanner. It may be a galvano scanner, a polygon scanner, or other scanning means. Further, the present invention may supply a program that realizes one or more functions of the above-described embodiment to a system or device via a network or a storage medium. In this case, it can also be realized by a process in which one or more processors in the computer of the system or device reads and executes the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Further, the present invention is not limited to the above-described embodiment, and various modifications and modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the case where the object to be measured is an eye is described, but it is also possible to apply the present invention to an object to be measured such as skin or an organ other than the eye. In this case, the present invention has an aspect as a device for medical imaging such as an endoscope other than the ophthalmologic imaging apparatus. Therefore, it is desirable that the present invention is grasped as an imaging apparatus exemplified by an ophthalmologic imaging apparatus, and the eye to be inspected is grasped as one aspect of an object to be inspected.

Claims (17)

Luminous flux projection means that projects luminous flux onto the object to be inspected,
An image signal acquisition means for acquiring an image signal based on the reflected light of the luminous flux from the object to be inspected, and
A scanning means included in the luminous flux projection means and scanning the luminous flux on the object to be inspected.
An image generation means that generates an image based on the acquired image signal, and
A position information generating means arranged outside the optical path when the luminous flux projecting means projects the luminous flux onto the object to be inspected.
A control means for causing the scanning means to scan the position information generating means with the luminous flux, and
The position information generation means includes a correction means for correcting the timing of acquiring the image signal by the image signal acquisition means based on the position information obtained from the scanned light flux .
The timing of acquiring the image signal by the correction means correcting the imaging apparatus according to claim Rukoto runs continuously in the scanning of the object to be inspected of the light beam by said scanning means for obtaining the image signal. The correction means modulates the timing of acquiring the image signal, which was at equal time intervals, at non-equal time intervals, and sets the position where the light flux is reflected on the object to be inspected for acquiring the image signal at equal intervals. The photographing apparatus according to claim 1, wherein the photographing apparatus is characterized in that. The photographing apparatus according to claim 1 or 2 , wherein the scanning means includes a resonance type scanner. The position information generating means is a chart-like structure having a diffusion surface and a region arranged in parallel on the diffusion surface with a reflectance different from the reflectance of the diffusion surface.
The imaging device according to any one of claims 1 to 3 , wherein the position information is reflected light from the diffusion surface of the light flux and the region. The fourth aspect of claim 4 , wherein the region arranged in parallel is a linear region, and the scanning means is arranged in parallel with one direction when scanning the light flux in two directions. Shooting device. The photographing apparatus according to any one of claims 1 to 3 , wherein the position information generating means includes a sensor that receives the light flux. The process of projecting a luminous flux onto the object to be inspected by a luminous flux projection means,
A step of acquiring an image signal based on the reflected light of the luminous flux from the object to be inspected, and
A step of scanning the luminous flux on the object to be inspected by the scanning means included in the luminous flux projection means.
The step of generating an image based on the acquired image signal and
A step of causing the position information generating means arranged outside the optical path when the luminous flux projecting means projects the luminous flux onto the object to be inspected to perform scanning by the luminous flux using the scanning means.
Based on the position information obtained from the scanned light beam in said position information generating means, seen including and a step of correcting the timing of acquiring the image signal,
The imaging apparatus characterized in that the correction of the timing of acquiring the image signal in the correction step is continuously executed by scanning the light beam on the object to be inspected by the scanning means for obtaining the image signal. Control method. A program characterized by causing a computer to execute each step of the control method of the photographing apparatus according to claim 7 . Scanning means for scanning the measurement light emitted from the light source,
A first acquisition means for acquiring an image signal based on the return light of the measurement light from the eye to be inspected, and
A light receiving means capable of receiving the measurement light scanned by the scanning means and arranged at a position outside the scanning range of the measurement light with respect to the eye to be inspected.
A second acquisition means that acquires information indicating the operation of the scanning means based on the output from the light receiving means, and
A determination means for determining the timing of acquiring the image signal by the first acquisition means based on the information indicating the operation is provided .
The scanning means is a photographing device that continuously scans the measurement light on the light receiving means after scanning the measurement light on the eye to be inspected . The imaging device according to claim 9 , wherein the light receiving means is arranged at a position separated from the scanning center of the scanning means by a predetermined distance. The light receiving means includes a plurality of light receiving elements and includes a plurality of light receiving elements.
The imaging device according to claim 9 or 10 , wherein the second acquisition means acquires information indicating the operation based on the outputs of the plurality of light receiving elements. With an additional objective lens
The photographing apparatus according to any one of claims 9 to 11 , wherein the light receiving means is arranged between the objective lens and the scanning means. The scanning means is a resonant scanner.
The photographing apparatus according to any one of claims 9 to 11 , wherein the light receiving means is a photodiode. The photographing apparatus according to any one of claims 9 to 13 , wherein the scanning means scans the measurement light by reciprocating scanning. Scanning means for scanning the measurement light emitted from the light source,
A first acquisition means for acquiring an image signal based on the return light of the measurement light from the eye to be inspected, and
A member capable of irradiating the measurement light scanned by the scanning means and having a pattern arranged at a position outside the scanning range of the measurement light with respect to the eye to be inspected.
A second acquisition means for acquiring information indicating the operation of the scanning means based on the return light from the member irradiated with the measurement light, and
A determination means for determining the timing of acquiring the image signal by the first acquisition means based on the information indicating the operation, and a determination means.
The first acquisition means so as to repeatedly execute the acquisition of the image signal by the first acquisition means, the acquisition of information indicating the operation of the scanning means by the second acquisition means, and the determination of the timing of acquiring the image signal by the determination means. 1 acquisition means, the second acquisition means, the control means for controlling the determination means, and
A photographing device characterized by being provided with. The first acquisition step of acquiring an image signal based on the return light from the eye to be inspected for the measurement light emitted from the light source, and
Information indicating the operation of the scanning means is acquired based on the output from the light receiving means that can receive the measurement light scanned by the scanning means and is arranged at a position outside the scanning range of the measurement light with respect to the eye to be inspected. The second acquisition process and
A determination step of determining the timing of acquiring the image signal in the first acquisition step based on the information indicating the operation is included.
A control method for a photographing apparatus, which repeatedly executes the first acquisition step, the second acquisition step, and the determination step. The process of scanning the measurement light emitted from the light source by scanning means,
A step of acquiring an image signal based on the return light of the measurement light from the eye to be inspected, and
Information indicating the operation of the scanning means based on the output from the light receiving means that can receive the measurement light scanned by the scanning means and is arranged at a position outside the scanning range of the measurement light with respect to the eye to be inspected. And the process of getting
Including a step of determining the acquisition timing in the step of acquiring the image signal based on the information indicating the operation.
A method for controlling an imaging device, wherein the scanning means continuously scans the measurement light on the light receiving means after scanning the measurement light on the eye to be inspected.

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