JP2016013188A - Tomographic imaging apparatus and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tomographic imaging apparatus in which focus adjustment accuracy at the time of tomographic imaging has been improved.SOLUTION: A tomographic imaging apparatus includes a light source for generating light, light branching means for branching the light from the light source into reference light and measurement light, adjustment means for adjusting a focus position of the measurement light, light shielding means for shielding the reference light, and detection means for detecting the intensity of return light acquired by irradiating the measurement light to an object to be inspected in a state that the reference light is shielded by the light shielding means, and the intensity of interference light between the return light and the reference light in a state that the reference light is not shielded by the light shielding means. The adjustment means adjusts a focus position based on the intensity of the return light detected by the detection means in a state that the reference light is blocked by the light shielding means.

Description

  The present invention relates to a tomographic imaging apparatus and a control method thereof, and more particularly to a tomographic imaging apparatus used for observation of the fundus and the like and a control method thereof.

  Currently, an imaging apparatus (hereinafter also referred to as an OCT apparatus) using an optical coherence tomography (OCT) using interference by low-coherent light has been put into practical use. This is an apparatus capable of capturing a tomographic image of an inspection object with high resolution.

  In the OCT apparatus, light from a light source is divided into measurement light and reference light by a beam splitter or the like. The measurement light is irradiated to an object such as an eye through the measurement optical path. Then, the return light from the object to be inspected is combined with the reference light and guided as interference light to the detector via the detection light path. Here, the return light is reflected light or scattered light including information on the interface in the light irradiation direction with respect to the inspection object. A tomographic image of the object to be inspected can be obtained by detecting and analyzing the interference light between the return light and the reference light with a detector.

  As an OCT apparatus that acquires a tomographic image of an eye, an ophthalmologic photographing apparatus in which a fundus camera is combined with an OCT apparatus is known (Patent Document 1). There is also known an ophthalmologic photographing apparatus in which a scanning laser ophthalmoscope (SLO) is combined with an OCT apparatus (Patent Document 2).

  In such a composite apparatus, the focus position is adjusted while checking the focus state of the fundus front image obtained by the fundus camera optical system or the SLO optical system or the positional relationship of the focus index projected on the fundus on the display monitor. The fundus front image and the fundus tomographic image are focused. That is, the focus position obtained by focus adjustment of the fundus front image is applied to the OCT optical system.

JP 2012-223428 A JP 2009-291252 A

  However, such a composite apparatus requires a fundus camera optical system or an SLO optical system in addition to the OCT optical system, which complicates the configuration of the apparatus and increases the cost of the apparatus. In addition, since the focus position of the fundus front image and the focus position of the fundus tomographic image obtained by the OCT optical system do not always match, the accuracy of focus adjustment for the fundus tomographic image is not sufficient.

  An object of the present invention is to improve the accuracy of focus adjustment during tomographic image capturing.

  In order to solve the above problems, a tomographic imaging apparatus according to the present invention includes a light source for generating light, a light branching unit for branching light from the light source into reference light and measurement light, By adjusting the focus position of the measurement light, the light shielding means for shielding the reference light, and irradiating the inspection light with the measurement light in a state where the reference light is shielded by the light shielding means And a detecting means for detecting the intensity of the obtained return light and the intensity of the interference light between the return light and the reference light in a state where the reference light is not shielded by the light shielding means, and the adjustment The means adjusts the focus position based on the intensity of the return light detected by the detection means in a state where the reference light is shielded by the light shielding means.

  In the method for controlling a tomographic imaging apparatus according to the present invention, the return light and the reference light obtained by branching light from a light source into reference light and measurement light and irradiating the object with the measurement light. A tomographic imaging apparatus that generates a tomographic image based on interference light with the reference light, wherein the reference light is shielded by a light shielding means, and the measurement light is received by the light shielding means while the reference light is shielded by the light shielding means. Detecting the intensity of the return light obtained by irradiating the inspection object by the detection means, and adjusting the focus position of the measurement light by the adjustment means based on the intensity of the return light detected by the detection means. Features.

  According to the present invention, since the focus position is detected by the OCT optical system, it is possible to improve the accuracy of focus adjustment during tomographic image capturing.

It is a schematic diagram which shows the outline of the OCT apparatus in the 1st Embodiment of this invention. It is a figure which shows the relationship between the focus position and light intensity integrated value in the 1st Embodiment of this invention. It is a figure which shows the shape of the signal in the 1st Embodiment of this invention. It is a figure which shows the output signal in the 1st Embodiment of this invention. It is a figure which shows the tomographic image of the 1st Embodiment of this invention.

[First Embodiment]
Embodiments of the present invention will be described in detail below with reference to the drawings. What can be imaged by the apparatus of the present embodiment is, for example, a tomographic image of a human retina, anterior eye portion, or the like.

(Device configuration)
An example in which the Fourier-domain optical coherence tomography according to this embodiment is applied to a fundus tomographic imaging apparatus will be described with reference to FIG.

  Reference numeral 1 denotes a light source for generating light (low coherence light). In the present embodiment, an SLD (Super Luminescent Diode) light source having a center wavelength of 850 nm and a bandwidth of 50 nm is used as the light source 1. Note that an ASE (Amplified Spontaneous Emission) light source can also be applied to the light source 1. The light source 1 can also be an ultrashort pulse laser light source such as a titanium sapphire laser. As described above, the light source 1 may be anything that can generate low-coherence light. Further, the wavelength of light generated from the light source 1 is not particularly limited, but is selected in the range of 400 nm to 2 μm depending on the object to be inspected. The wider the wavelength band, the better the vertical resolution. In general, when the center wavelength is 850 nm, the vertical resolution is 6 μm in the 50 nm band and 3 μm in the 100 nm band.

  Reference numerals 2, 4, 10, and 14 denote light guide sections formed of optical fibers or the like. The light emitted from the light source 1 is guided to the light branching unit 3 by the light guide unit 2. A fiber coupler or the like can be applied to the optical branching unit 3. Note that an appropriate branching ratio is selected according to the object to be inspected.

  A collimator lens 5, an optical scanning unit 6, a focus lens 7, a wavelength branching mirror 8, and an objective lens 9 are disposed on the optical path of light (measurement light) branched to the light guide unit 4 side by the light branching unit 3. A sample arm 1001 is configured. As the optical scanning unit 6, a galvanometer mirror or a resonance mirror that is arranged adjacent to each other in the optical axis direction (tandem arrangement) and scans the measurement light in the X and Y directions orthogonal to each other is applied. The wavelength branching mirror 8 transmits light emitted from the light source 1 (wavelength: λ = 800 to 900 nm) and reflects light of the anterior ocular segment illumination (λ = 940 nm). The measurement light guided to the light guide 4 passes through the sample arm 1001 and reaches the fundus oculi Ef of the eye E to be examined.

  A collimator lens 11, a shutter 26, and a reference mirror 12 are arranged on the optical path of light (reference light) branched to the light guide unit 10 side by the light branching unit 3 to constitute a reference arm 1002. The shutter 26 is detachably disposed in the reference optical path. The reference mirror 12 is arranged on the linear motion stage 13 and adjusts the optical path length of the reference arm 1002 by moving the linear motion stage 13 in the optical axis direction.

  A lens 15, a spectroscopic unit 16 including a grating or a prism as a diffraction grating, an imaging lens 17, and an imaging unit 18 having a photoelectric conversion element such as a CMOS or a CCD constitute a spectroscope 1003. The light (interference light) from the light branching unit 3 is guided to the spectroscope 1003 by the light guide unit 14 connected to the light branching unit 3.

  Reference numeral 19 denotes a control unit that controls the optical scanning unit 6, the linear motion stage 13, the imaging unit 18, the shutter 26, and the like. A display unit 20 is connected to the control unit 19. The control unit 19 is connected to a memory 24 and a pointing device 25 such as a mouse.

  Anterior segment illumination light sources 21 a and 21 b are arranged around the objective lens 9, and an image of the anterior segment of the eye E illuminated by these light sources passes through the objective lens 9 and is reflected by the wavelength branch mirror 8. The lens 22 forms an image on the imaging surface of the two-dimensional imaging unit 23.

  In this embodiment, a Michelson interference system is used as the interference system, but a Mach-Zehnder interference system may be used.

(Imaging method)
Next, a method for capturing a tomographic image of the retina of the fundus oculi Ef of the eye E using the apparatus having such a configuration will be described.

  When the eye E is placed in front of the present apparatus, the anterior eye portion of the eye E is illuminated with light emitted from the light sources 21a and 21b. The image of the anterior segment illuminated in this way passes through the objective lens 9, is reflected by the wavelength branching mirror 8, and forms an image on the imaging surface of the imaging unit 23 by the lens 22. The video signal from the imaging unit 23 is input to the control unit 19 and converted into digital data in real time, and an anterior ocular segment image is generated.

  The control unit 19 determines the eccentricity and focus state of the eye E based on the iris pattern in the anterior eye image of the eye E. Since the center of the imaging surface and the optical axis of the optical system of the sample arm 1001 are adjusted to coincide with each other, the eccentric amount between the pupil center and the imaging center of the anterior segment image captured by the imaging unit 23 is the same as that of the eye E. This corresponds to the amount of eccentricity of the optical system of the sample arm 1001. The optical system of the sample arm 1001 is arranged on a stage (not shown) so that the position of the eye E can be adjusted in the vertical and horizontal directions and in the optical axis direction. Therefore, as described above, the vertical and horizontal positions are adjusted so that the center of the pupil coincides with the optical axis, and the optical axis direction is adjusted so that the contrast of the iris pattern is the highest.

  Thereby, the distance (working distance) between the pupil of the eye E to be examined and the objective lens 9 of the optical system of the sample arm 1001 which is flush with the iris is kept constant. The anterior segment image is displayed in the display area 20a of the display unit 20, and the operator can confirm the optical axis decentering from this image.

  In this way, when the amount of eccentricity becomes a predetermined value or less by auto-alignment, the control unit 19 turns on the light source 1 and inserts the shutter 26 into the reference optical path to shield the reference light. Further, the photoelectric conversion element of the imaging unit 18 is operated at a predetermined frame rate, and signal detection for focus adjustment is started. The light from the light source 1 is guided to the light branching unit 3 by the light guide unit 2 and branched such that the ratio of the amount of light guided to the light guide unit 4 and the light guide unit 10 is 1: 9, for example. The measurement light guided to the light guide 4 side reaches the fiber end 4a. Measurement light emitted from the fiber end 4 a as a point light source is converted into parallel light by the collimator lens 5, passes through the optical scanning unit 6, the focus lens 7, and the wavelength branching mirror 8, and passes through the pupil of the eye E to be examined by the objective lens 9. Ef is irradiated.

  Return light reflected and scattered by a plurality of layers constituting the retina of the fundus oculi Ef returns to the same optical path as that at the time of irradiation, enters the light guide unit 4 from the fiber end 4a through the collimator lens 5, and enters the light branching unit 3. Led. The light branching unit 3 is branched so that the ratio of the amount of light guided to the light guide unit 2 and the light guide unit 14 is 1: 9. The light emitted from the fiber end 14 a through the light guide unit 14 is converted into parallel light by the collimator lens 15 and enters the spectroscopic unit 16. In the spectroscopic unit 16, a plurality of diffraction gratings having dimensions close to the wavelength of light are formed at equal intervals, and the incident light is dispersed by diffraction. Since the diffraction angle varies depending on the wavelength, the diffracted light is imaged as a line image by the imaging lens 17 in the linear imaging region of the imaging unit 18. That is, the light emitted from the fiber end 14a forms an image as a split slit image. Therefore, a signal corresponding to the intensity for each wavelength is output from the imaging unit 18.

  Here, the output of the imaging unit 18 is stored in the memory 24 in correspondence with the focus position while changing the focus position by moving the focus lens 7 in the optical axis direction. The focus lens 7 is, for example, an eye diopter and moves in a range corresponding to −15D to + 15D in 0.25D steps. At this time, since the reference light is shielded by the shutter 26, the imaging unit 18 detects only the intensity of the return light from the fundus oculi Ef.

  Further, the photoelectric conversion element of the imaging unit 18 operates at a predetermined frame rate of, for example, about 70 Hz so that the intensity of weak return light from the fundus oculi Ef can be detected. Here, if the frame rate is made slower, the exposure accumulation time increases, which is advantageous for detecting weaker light intensity. The control unit 19 calculates an integrated value of the intensity of light of all wavelengths received from the output data of the imaging unit 18 at each focus position stored in the memory 24.

  FIG. 2 is a diagram illustrating an output of an integrated value of the intensity of the return light with respect to the focus position. Since the integrated value of the intensity of the return light reaches a peak when the focus position matches the fundus oculi Ef, the focus lens 7 is moved to the peak position to focus on the fundus oculi Ef.

  When detecting the completion of the focus adjustment, the control unit 19 detaches the shutter 26 from the reference optical path, and operates the photoelectric conversion element of the imaging unit 18 at a predetermined frame rate. The light guided from the light branching unit 3 to the light guide unit 10 is emitted from the fiber end 10 a, converted into parallel light by the lens 11, and travels toward the reference mirror 12. The reference mirror 12 is disposed on the linear motion stage 13 so as to be movable perpendicularly to the parallel light and in the optical axis direction. As a result, the optical path lengths of the reference optical path and the measurement optical path can be matched to the eye E having different axial lengths.

  The reference light reflected by the reference mirror 12 is condensed on the fiber end 10a of the light guide unit 10 by the lens 11, guided to the light branch unit 3 by the light guide unit 10, and branched to the light guide unit 2 and the light guide unit 14. Is done. The branching ratio at this time is 9: 1 opposite to the return light from the eye E. Then, the light guided to the light guide unit 14 becomes interference light by combining with the return light from the fundus oculi Ef, enters the spectroscope 1003, is split by the spectroscopic unit 16, and as described above, The photoelectric conversion element forms an image on a light receiving region arranged on the line.

  Here, the photoelectric conversion element of the imaging unit 18 operates at a predetermined frame rate of, for example, about 70 kHz, which is faster than the focus adjustment. Since the intensity of the interference light between the reference light and the return light becomes larger than the intensity of the return light alone due to the interference, the influence of noise during signal detection can be suppressed even if the frame rate is increased accordingly.

  Further, by increasing the frame rate, a signal in a wider area on the fundus can be obtained in a short time. A signal from the imaging unit 18 is input to the control unit 19, and a tomographic image is generated and displayed on the display area 20 b of the display unit 20. The control unit 19 detects the luminance of the tomographic image and adjusts the position of the reference mirror 12 (coherence gate adjustment) so that the tomographic image of the region of interest is positioned at a predetermined position in the display area 20b. The control unit 19 moves the position of the linear motion stage 13 in the instructed direction, and changes the control position information of the linear motion stage 13 stored in the memory 24 according to the amount of movement. The linear motion stage is driven and controlled by a stepping motor (not shown), and the position of the linear motion stage 13 corresponds to the number of steps instructed to the stepping motor. For example, when a 60 mm stroke is driven in 60000 steps, the amount of movement per step is 1 μm. The number of steps from 0 to 60000 corresponds to the 0 to 60 mm position of the linear motion stage.

  Further, since the distance from the reference position of the linear motion stage 13 to the lens 11 is accurately designed, and the relationship between the reference position and the stage position is also clear in design, the reference optical path length is determined from the number of steps. Can be calculated. As described above, the optical path length of the reference optical path changes as the position of the reference mirror 12 changes. As a result, the display position of the tomographic image in the display area 20b changes. Thus, the position of the reference mirror 12 is always stored in the memory 24. After the above imaging preparation, when the imaging button 20e is instructed, a still image of a tomographic image is captured. Thereby, the captured tomographic image is stored in the memory 24.

(Tomographic image generation)
Next, generation of a tomographic image will be described.

  During tomographic imaging, interference light between the return light from the fundus oculi Ef of the eye E and the reference light reflected from the reference mirror 12 is guided to the light guide unit 14. Due to the difference between the optical path length from the optical branching section 3 to the fundus oculi Ef and the optical path length from the optical branching section 3 to the reference mirror 12, the return light and the reference light have a phase difference when combined at the optical branching section 3. . Since this phase difference varies depending on the wavelength, interference fringes are generated in the spectral intensity distribution appearing on the light receiving region of the imaging unit 18. In addition, since the retina has a plurality of layers, and the return light from each layer boundary has a different optical path length, the interference fringes include interference fringes having different frequencies. From the frequency of interference fringes included in the intensity distribution and the intensity thereof, the position of the reflecting object and the brightness corresponding to the reflection / scattering from the position can be obtained.

  In the B scan mode for scanning one line on the fundus, the control unit 19 drives only one of the X and Y scan mirrors of the optical scanning unit 6, for example, the X scan mirror, while Read the output. Data indicating the angle of the scan mirror is output from the optical scanning unit 6, and the read signal is converted into digital data together with the angle of the scan mirror, and further converted into an angle θi at which the light irradiates the eye to be examined. And stored in the memory 24. The angle of the scan mirror and the irradiation angle θi of the light beam correspond to each other and are obtained from the design value of the optical system.

  FIG. 3 shows the light intensity distribution on the imaging unit 18 at the scan mirror angle θi. The horizontal axis is the sensor position on the imaging unit 18 and corresponds to the wavelength. The vertical axis represents the signal intensity. Here, the waveform due to the interference fringes overlaps the intensity distribution of the center wavelength λ0 and the half-value width δλ.

  The intensity information of this waveform is read out, converted into digital data by an A / D converter (not shown), and stored in the memory 24. When this data is subjected to wave number conversion and frequency conversion, an intensity distribution as shown in FIG. 4 is obtained. This indicates that the interference intensities at the distances h1, h2, and h3 (distance from the coherence gate) are I1, I2, and I3. Therefore, the interference intensity is measured while changing the angle θi of the scan mirror from θs to θe. The interference intensity I (θi, hj) acquired in this way is displayed with θ on the horizontal axis and h on the vertical axis, so that a B-scan image of the fundus (image based on the optical distance) as shown in FIG. Can be displayed.

  As described above, according to the present embodiment, by adjusting the focus position based on the intensity of the return light from the fundus of the measurement light, a fundus camera optical system or an SLO optical system is not provided separately from the OCT optical system. Thus, a focused fundus tomographic image can be obtained with a simple apparatus configuration. Furthermore, since the focus position is detected by the OCT optical system, the focus accuracy of the fundus tomographic image can be improved.

[Second Embodiment]
In the first embodiment, the measurement light is not scanned during focus adjustment, but may be scanned. The output of the imaging unit 18 that detects the intensity of the return light also depends on the reflectance of the fundus. Since the fundus reflectance varies depending on the position on the fundus, if the eye moves during focus adjustment, the output of the imaging unit 18 changes not only due to the influence of the focus position change but also due to the fundus reflectance change. End up. When the output changes, an error occurs in the detection of the peak position of the integrated value of the return light intensity, and an error occurs in the detection of the focus position. Therefore, for example, the measurement light may be scanned in a circle in synchronization with the movement step of the focus position. As a result, the influence of the reflectance of the fundus that irradiates the measurement light is averaged on the circle, so even if the position on the fundus where the measurement light is irradiated changes due to movement of the eye, the focus position is detected. The effect of.

  Here, since the reflectance of the fundus is particularly high in the optic disc, if there is a step in which the optic disc is included in the scan range and a step in which the scan range is not included in each step of moving the focus position, the change in the output of the imaging unit 18 is thereby caused. This increases the influence on the detection of the focus position. In order to suppress the influence, for example, the measurement light may be a circle scan having a size that fits between the macula and the optic disc so that the scan range does not include the optic disc. Further, when the measurement light is scanned, the irradiation limit light amount that is restricted in terms of laser safety is reduced as compared with the case where the measurement light is not scanned. Thereby, the intensity of the irradiation light of the measurement light can be increased, and the intensity of the return light can be increased accordingly, so that the influence of noise when detecting the intensity of the return light can be reduced.

  According to the present embodiment, it is possible to adjust the focus by scanning the measurement light while suppressing the influence of the eye movement and the influence of the noise of the detector.

[Third Embodiment]
In the first embodiment, the control unit 19 performs the focus adjustment and the optical path length adjustment. However, the focus position may be further finely adjusted thereafter. After detecting the completion of the optical path length adjustment, the control unit 19 stores the luminance value of the tomographic image at each focus position in the memory 24 while moving the focus lens 7 in the optical axis direction to slightly change the focus position. . Then, the focus lens 7 is adjusted to a focus position where the luminance value reaches a peak. For example, with the focus position after the focus adjustment performed in the first embodiment as the origin, the focus lens 7 is moved in the range of −1D to + 1D in 0.1D steps with the diopter of the eye, and the luminance of the tomographic image reaches a peak. The focus lens 7 is moved to the position.

  According to the present embodiment, fine adjustment of the focus position is further performed after the optical path length adjustment, so that it is possible to focus on the image at the desired coherence gate position with higher accuracy.

[Fourth Embodiment]
In the first to third embodiments, the control unit 19 performs the auto focus adjustment and the auto optical path length adjustment. However, the operator may perform fine adjustment manually thereafter. The operator observes the tomographic image displayed in the display area 20b of the display unit 20, and performs focus adjustment by operating the button of the display area 20c with the cursor using the pointing device 25 so that the tomographic image becomes brightest. . Similarly, the position adjustment (coherence gate adjustment) of the reference mirror 12 is performed by operating the button of the display area 20d so that all the tomographic images of the region of interest fall within the desired area of the display area 20b.

  According to the present embodiment, a tomographic image of a desired focus position and a desired coherence gate position can be obtained by performing manual adjustment after auto focus adjustment and auto optical path length adjustment.

[Fifth Embodiment]
In the first to fourth embodiments, automatic adjustment is performed by the control unit 19, but the operator may manually perform focus adjustment and optical path length adjustment. The operator operates the display changeover switch 20f to display the integrated value of the intensity of the return light in the display area 20b. At this time, by the switch operation, the control unit 19 inserts the shutter 26 into the reference optical path to shield the reference light, and the photoelectric conversion element of the imaging unit 18 is detected, for example, about 70 Hz to detect weak return light intensity. To operate at a predetermined frame rate. The operator operates the button of the display area 20c with the cursor using the pointing device 25, and performs focus adjustment so that the integrated value of the intensity of the displayed return light reaches a peak. When the focus adjustment is completed, the display changeover switch 20f is operated again. By this switch operation, the control unit 19 detaches the shutter 26 from the reference optical path, and operates the photoelectric conversion element of the imaging unit 18 by changing to a predetermined frame rate of, for example, about 70 kHz in order to observe a tomographic image. Thereby, a tomographic image is displayed in the display area 20b. As in the fourth embodiment, the operator operates the buttons of the display area 20c and the display area 20d while observing the tomographic image, and performs focus adjustment and coherence gate adjustment.

  According to the present embodiment, the focus position and the coherence gate position can be adjusted by performing manual adjustment while observing the return light intensity, even when an error occurs during automatic adjustment by the control unit 19.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the object to be inspected is an eye has been described, but the present invention can also be applied to an object to be inspected other than the eye, such as skin or organ. In this case, the present invention has an aspect as a medical device such as an endoscope other than the ophthalmologic apparatus. Therefore, it is desirable that the present invention is grasped as a tomographic imaging apparatus exemplified by an ophthalmologic apparatus, and the eye to be examined is grasped as one aspect of the inspection object.

  Further, by executing the program code read by the computer, an operating system (OS) or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. This is also included.

  Furthermore, the program code read from the recording medium is written in the memory in the function expansion card or function expansion unit attached to the computer, and the arithmetic device in the expansion card or expansion unit performs part or all of the actual processing, This includes the case where the functions of the above-described embodiments are realized.

Claims (8)

A light source for generating light;
Light branching means for branching light from the light source into reference light and measurement light;
Adjusting means for adjusting the focus position of the measurement light;
A light shielding means for shielding the reference light;
The intensity of the return light obtained by irradiating the inspection light with the measurement light in a state where the reference light is shielded by the light shielding means, and the return light in a state where the reference light is not shielded by the light shielding means. And detecting means for detecting the intensity of interference light with the reference light,
The tomographic image pickup apparatus, wherein the adjusting unit adjusts the focus position based on the intensity of the return light detected by the detecting unit in a state where the reference light is blocked by the light blocking unit.   2. The tomographic imaging according to claim 1, wherein the detection unit detects the return light while moving the focus position by the adjustment unit, and adjusts the focus position to a position where the return light reaches a peak. apparatus.   3. The tomographic imaging apparatus according to claim 1, wherein the detection unit operates at a slower frame rate when detecting the intensity of the return light than when detecting the interference light. 4.   The said adjustment means is further provided with the scanning means which scans the said to-be-inspected object in a circle shape with the said measurement light synchronizing with the movement of a focus position, when the said adjustment means adjusts the said focus position. Item 4. The tomographic imaging apparatus according to Item 2 or 3.   The tomographic image of the inspection object is generated by detecting the interference light in a state where the reference light is not shielded by the light shielding unit after the focus position is adjusted. The tomographic imaging apparatus according to any one of 1 to 4. Optical path length adjusting means for adjusting any one of the optical path length of the reference light and the optical path length of the measurement light;
The luminance of the tomographic image is detected while changing the optical path length by the optical path length adjusting unit, and the optical path length is adjusted by the optical path length adjusting unit so that the tomographic image is at a predetermined position in a display area. The tomographic imaging apparatus according to claim 5.   After the adjustment of the optical path length, the brightness of the tomographic image is further detected while the focus position is changed by the adjustment means, and the focus position is adjusted by the adjustment means at a position where the brightness reaches a peak. The tomographic imaging apparatus according to claim 6, wherein A tomographic imaging apparatus for branching light from a light source into reference light and measurement light, and generating a tomographic image based on interference light between return light obtained by irradiating the object to be inspected with the measurement light and the reference light Control method,
Shielding the reference light by a light shielding means;
The detection means detects the intensity of the return light obtained by irradiating the inspection light with the measurement light in a state where the reference light is shielded by the light shielding means,
A method for controlling a tomographic imaging apparatus, comprising: adjusting a focus position of the measurement light based on an intensity of the return light detected by the detection means;

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