JP2017169863A - Optical coherence tomography apparatus and actuation method for optical coherence tomography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a difference in polarization states between measurement light and reference light caused by a temperature change between an optical fiber for guiding the measurement light and an optical fiber for guiding the reference light.SOLUTION: An optical coherence tomography apparatus includes: detection means for detecting multiplexed light formed by multiplexing return light from a subject irradiated with measurement light, and reference light corresponding to the measurement light; a first optical fiber disposed at an optical path of the reference light and guiding the reference light; a second optical fiber disposed at an optical path of the measurement light and the return light for guiding the measurement light and return light; first storage means for storing the detection means; and second storage means different from the first storage means, for storing the first optical fiber and second optical fiber.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical coherence tomography apparatus that captures a tomographic image of an object to be examined such as an eye to be inspected, and an operation method of the optical coherence tomography apparatus.

  An optical coherence tomography (hereinafter referred to as OCT) using multiwavelength lightwave interference can obtain a tomographic image of a sample (particularly the fundus) with high resolution. In the OCT, the light from the light source is divided into measurement light and reference light, the return light from the sample irradiated with the measurement light in the measurement optical system, and the reference light that passes through the reference optical system that adjusts the optical path length. A tomographic image is obtained from the interference light obtained by combining the two.

  In recent years, in an OCT apparatus to which this OCT is applied for ophthalmology, in addition to a normal OCT image for imaging the shape of the fundus tissue, an attempt has been made to acquire an image by the function OCT for imaging optical characteristics and movement of the fundus tissue. Yes.

  In polarization OCT, which is one of functional OCTs, imaging is performed using a polarization parameter (retardation and orientation, which will be described later), which is one of the optical characteristics of the fundus tissue. By using the polarized OCT, a so-called polarized OCT image can be formed, and fundus tissue can be distinguished or segmented. In polarized light OCT, light that has been modulated into circularly polarized light is used as measurement light for observing a sample, and interference light obtained from the measurement light is divided into two orthogonal linearly polarized lights, and each of them is detected. Then, based on each obtained polarization parameter (polarization parameter), a polarization OCT image is generated (see Non-Patent Document 1).

Since polarization OCT images tissue parameters by imaging polarization parameters, a desired image may not be obtained if the polarization of measurement light or the like changes due to the apparatus. Therefore, it is necessary to reduce the polarization change caused by the apparatus as much as possible.
Here, in a normal OCT apparatus, Patent Document 1 discloses that a change in the polarization state in the optical path of the measurement light and the optical path of the reference light due to a change in the holding environment of the apparatus such as temperature and vibration is suppressed. ing. Specifically, when a single-mode or multi-mode optical fiber is used for guiding measurement light and reference light, interference light cannot be suitably generated due to the influence of changes in the holding environment. This is because the polarization axis directions of the measurement light and the reference light do not coincide with each other due to a change in the holding environment. On the other hand, in the optical image measurement device disclosed in Patent Document 1, in order to obtain interference light even when an environmental change such as temperature occurs, measurement light and reference light are respectively used. A polarization-maintaining fiber is used as an optical fiber leading to the optical system.

JP 2007-178409 A

IOVS, December 2008, Vol. 49, no. 12, Christoph K. Hizenberger et al. “Analysis of the Origin of Atypical Scanning Laser Polarimetric Patterns by Polarization-Sensitive Optical Coherence Tomography”

  Here, even when a polarization-maintaining fiber is used as the optical fiber that guides light to the measurement optical system and the reference optical system described above, the length, birefringence, and the like are not completely changed by temperature change. For this reason, if the temperature change of the fiber of the measurement optical system is different from the temperature change of the fiber of the reference optical system, a difference occurs in the polarization state of the measurement light and the reference light, and an accurate interference signal may not be obtained. was there.

  One of the objects of the present invention has been made in view of such a situation, and the polarization state of the measurement light and the reference light caused by the temperature change between the optical fiber that guides the measurement light and the optical fiber that guides the reference light. Is to reduce the difference.

In order to achieve the above object, an optical coherence tomography apparatus according to an aspect of the present invention is provided.
Detection means for detecting combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
A first optical fiber disposed in the optical path of the reference light and guiding the reference light;
A second optical fiber disposed in the optical path of the measurement light and the return light to guide the measurement light and the return light;
First storage means for storing the detection means;
And a second storage means for storing the first optical fiber and the second optical fiber, the second storage means being different from the first storage means.

  According to the present invention, even if the temperature in the apparatus changes, the difference in the polarization state of the measurement light and the reference light that occurs due to the temperature change between the optical fiber that guides the measurement light and the optical fiber that guides the reference light is reduced. be able to.

1 is a diagram illustrating an outline of an overall configuration of an optical coherence tomography apparatus according to an embodiment of the present invention. It is explanatory drawing which showed typically the relative position shift of a P wave tomographic image and an S wave tomographic image. It is a figure which shows the example of the accommodating means of the tomographic imaging apparatus which concerns on one Embodiment. It is a figure which shows the modification of the accommodating means of the tomographic imaging apparatus which concerns on one Embodiment. It is a figure which shows another modification of the accommodating means of the tomographic imaging apparatus which concerns on one Embodiment. It is a figure which shows another modification of the accommodating means of the tomographic imaging apparatus which concerns on one Embodiment. It is the figure which showed typically the relationship between the relative positional offset amount of the P wave tomographic image and the S wave tomographic image with respect to temperature.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the configurations exemplified in the following embodiments do not limit the present invention related to the scope of claims, and all the combinations of features described in the present embodiments are essential for the solving means of the present invention. Not necessarily.

[Overall configuration of the device]
FIG. 1 is a diagram showing an outline of the overall configuration of an optical coherence tomography apparatus according to an embodiment of the present invention. This optical coherence tomography apparatus includes a polarization OCT (Polarization Sensitive OCT; hereinafter referred to as PS-OCT) unit 100 and a control unit 200.

<Configuration of PS-OCT unit 100>
The configuration of the PS-OCT unit 100 will be described below.

  In the PS-OCT unit 100, an SLD light source (Super Luminescent Diode) that is a low coherent light source is used as the light source 101. For example, the SLD light source emits light having a center wavelength of 850 nm and a bandwidth of 50 nm. Although an SLD light source is used here as the light source 101, any light source capable of emitting low-coherent light, such as an ASE light source (Amplified Spontaneous Emission), may be used.

  Light emitted from the light source 101 is guided to the fiber coupler 104 via the SM (Single Mode) fiber 134, the polarization controller 103, the connector 135, and the polarization maintaining fiber 102. The fiber coupler 104 functions as a light splitting unit having a polarization maintaining function. The light guided to the fiber coupler 104 is divided into measurement light (also referred to as OCT measurement light) and reference light (also referred to as reference light corresponding to the OCT measurement light) by the fiber coupler 104.

  The polarization controller 103 is used to adjust the polarization state of the light emitted from the light source 101. The emitted light is adjusted to linearly polarized light by the polarization controller 103.

  The measurement light split by the fiber coupler 104 is emitted as collimated light from the collimator 106 via the polarization maintaining fiber 105. The emitted measurement light is guided to the fundus Er of the eye 115 through the X scanner 107, the lens 108, the lens 109, the Y scanner 110, the mirror 111, the lens 112, and the λ / 4 polarizing plate 113.

  The X scanner 107 is composed of a galvanometer mirror that scans the measurement light in the horizontal direction on the fundus oculi Er. The Y scanner 110 includes a galvanometer mirror that scans measurement light in the vertical direction on the fundus Er. The X scanner 107 and the Y scanner 110 are controlled by the drive control unit 180 and scan the measurement light in a desired range of the fundus Er (also referred to as a tomographic image acquisition range, a tomographic image acquisition position, and a measurement light irradiation position). be able to.

  The measurement light reflected by the mirror 111 passes through the lens 112 and passes through a λ / 4 polarizing plate 113 (an example of a polarization adjusting member) that is installed at an angle of 45 ° in a plane perpendicular to the optical axis of the measurement light. By passing through the λ / 4 polarizing plate 113, the phase of the measurement light is shifted by 90 °, and the measurement light is polarization-controlled to circularly polarized light. Note that the λ / 4 polarizing plate 113 is disposed at an angle with respect to the optical axis at an angle (an example of an arrangement state) corresponding to the inclination from the optical axis of the polarization splitting surface of the fiber coupler 123 including the polarization beam splitter, for example. It is preferred that In the present embodiment, the λ / 4 polarizing plate 113 is installed so as to be inclined from P-polarized light to S-polarized light by 22.5 ° in a plane perpendicular to the optical axis of the measurement light.

  The measurement light whose polarization is controlled to be circularly polarized is focused on the retinal layer of the fundus Er via the anterior segment Ea of the eye 115 to be examined. The measurement light irradiated on the fundus Er is reflected or scattered by each retinal layer, is emitted from the eye 115 as return light, and passes through the optical path including the polarization maintaining fiber 105 that guides the return light. Return to. The measurement light passes through the λ / 4 polarizing plate 113 twice to become linearly polarized light, and returns to the fiber coupler 104 in this state. In this embodiment, the polarization maintaining fiber 105 is arranged in a path where the measurement light emitted from the fiber coupler 104 is incident on the fiber coupler 104 again as return light, and guides the measurement light and return light. Light guiding means (second optical fiber).

  The reference light divided by the fiber coupler 104 is emitted as collimated light from the collimator 118 through the polarization maintaining fiber 117 for guiding the reference light. Like the measurement light, the emitted reference light is polarization-controlled by a λ / 4 polarizing plate 119 that is installed by tilting from P-polarized light to S-polarized light by 22.5 ° in a plane perpendicular to the optical axis of the reference light. The The reference light is further reflected by the mirror 122 on the coherence gate stage 121 via the dispersion compensation glass 120, and returns to the fiber coupler 104 along the same optical path. The reference light passes through the λ / 4 polarizing plate 119 twice to become linearly polarized light, and returns to the fiber coupler 104 in this state. In this embodiment, the polarization maintaining fiber 117 is arranged in a path where the reference light emitted from the fiber coupler 104 is incident on the fiber coupler 104 again, and guides the reference light (first light guiding means ( 1st optical fiber) is comprised.

  Note that the optical path length of the reference light needs to be changed according to the difference in the axial length of the subject. For this reason, the coherence gate stage 121 is controlled by the drive control unit 180 so as to move in the optical axis direction of the reference light, and drives and controls the position of the mirror 122 on the reference light path.

  By the way, a polarization maintaining fiber, for example, a PANDA (Polarization-Maintaining AND Absorption-Reducing) fiber gives a large birefringence in the fiber so that the polarization plane can be maintained even if the refractive index of the fiber changes due to an external force or the like. It has a simple structure. However, since there is birefringence, between the polarization component oriented along the slow axis (hereinafter referred to as slow axis polarization) and the polarization component oriented along the fast axis perpendicular to the slow axis (hereinafter referred to as fast axis polarization). Therefore, the propagation speed in the fiber is different.

  For example, when light comprising fast axis polarization is incident on the incident end of the PANDA fiber, both the polarization components of the fast axis polarization and the slow axis polarization leaked from the fast axis polarization due to cross coupling are emitted. The That is, when light of two velocities is generated in the fiber and the light is reflected, for example, at the end of the fiber, it interferes with each other to generate interference light. This interference light generates an interference signal corresponding to a position corresponding to the optical path length difference of each polarized light, and as a result, noise occurs in the OCT interference signal. As a method for avoiding this, it is conceivable to select a fiber length so that the optical path length difference in the fibers of orthogonal polarization components is larger than the imaging depth range of OCT. As an example of this method, the case where the OCT imaging depth range is 2 mm will be described below.

  In general, a beat length indicating a length in which a phase difference between a slow axis polarization and a fast axis polarization propagating through a fiber is equivalent to one wavelength (2π) is described as a specification of the polarization maintaining fiber.

  Here, beat length: LB = λ / B, λ: wavelength, and B: birefringence.

  Since birefringence is the difference in refractive index between the slow axis and the fast axis, if the birefringence multiplied by the fiber length becomes larger than the OCT imaging depth range, the optical path in the fiber of orthogonal polarization components The length difference exceeds the OCT imaging depth range. Therefore, under this condition, noise due to interference between the two polarization components appears outside the imaging range.

Therefore, the fiber length LF necessary to avoid the influence of noise due to the above-mentioned interference is 2 mm for the OCT imaging depth range (z), 3 mm for the beat length (LB), 850 nm for the wavelength used (λ), fiber If the refractive index (nf) is 1.5,
LF = z × nf × LB / λ
It becomes 10.6 m by the following relational expression. Therefore, the lengths of the polarization maintaining fiber 105 as the second light guide unit and the polarization maintaining fiber 117 as the first light guide unit in the present embodiment are set to the required fiber length LF = 10. It must be longer than 6m. That is, the polarization maintaining fiber needs to have a length of at least 10 m.

  The measurement light (return light) that has returned to the fiber coupler 104 serving as a multiplexing means and the reference light are combined by the fiber coupler 104 to be combined light (interference light). The combined light is then guided to a fiber coupler 123 which is a polarization splitting means incorporating a polarization beam splitter. The combined light is split by the fiber coupler 123 into light of different polarization directions (in this embodiment, P-polarized light and S-polarized light, which are different polarizations) at a split ratio of 50:50.

  The P-polarized light after the division is split by the grating 131 through the polarization maintaining fiber 124 and the collimator 130, and further received by the line camera 133 which is a detection means through the lens 132. Similarly, the split S-polarized light is split by the grating 127 via the polarization maintaining fiber 125 and the collimator 126, and further received by the line camera 129 as detection means via the lens 128. Note that the gratings 127 and 131 and the line cameras 129 and 133 are arranged in accordance with the directions of the corresponding polarizations.

  The light received by the line cameras 129 and 133 is output as an electrical signal corresponding to the intensity of the light, and the electrical signal is received by the signal processing unit 190. These line cameras constitute detection means for detecting lights of different polarizations obtained by dividing the combined light.

<Control unit 200>
Next, the control unit 200 for controlling the entire apparatus in the present embodiment will be described.

In the present embodiment, the control unit 200 includes a drive control unit 180, a signal processing unit 190, a display control unit (not shown), and a display unit (not shown).
The drive control unit 180 controls each unit of the PS-OCT unit 100 as described above.

  The signal processing unit 190 includes an image generation unit 191 that is an image generation unit and an image analysis unit 192 that is an image analysis unit. The image generation unit 191 generates a plurality of tomographic images such as a tomographic image based on each polarized light and a luminance image, a retardation image, and a DOPU image, which will be described later, based on the different polarized lights described above. The image analysis unit 192 performs various analysis processes such as identification of each layer of the retina and discrimination of blood vessels based on the obtained image. The signal processing unit 190 uses these units to generate an image, analyze the generated image, and generate analysis result visualization information based on signals output from the detectors such as the line cameras 129 and 133. Do. Details of image generation and analysis will be described later.

  A display control unit (not shown) displays an image or the like acquired or generated from the signal processing unit 190 on a display screen of a display unit exemplified by a display such as a liquid crystal display.

[Image processing]
<Tomographic image generation and fundus image generation>
The image generation unit 191 described above performs reconfiguration processing used for general SD-OCT (Spectral Domain OCT) on the interference signals output from the line cameras 129 and 133. Specifically, the image generation unit 191 generates a tomographic signal (also referred to as a tomographic signal indicating a polarization state) by performing processing such as Fourier transform on the interference signal. By performing this processing on each of the interference signals of the two polarization components, two tomographic signals A _H and A _V are generated. In the present embodiment, these faults signals A _H, based on A _V, the P-wave tomographic image and the S-wave tomographic image is generated, respectively.

<Luminance image generation>
The image generation unit 191 further generates a luminance image different from the above-described tomographic image from the above-described two tomographic signals.
The luminance image is basically the same as the tomographic image in the conventional OCT, and is generated based on the pixel value of each pixel in the signal acquisition region. However, the pixel value r is calculated by Equation 1 from the tomographic signals _{A H} and _{A V} obtained from the line camera 129 and 133.

<Retardation image generation>
The image generation unit 191 further generates a retardation image from tomographic images of polarization components orthogonal to each other.

The value δ of each pixel of the retardation image is obtained by quantifying the phase difference between the vertical polarization component and the horizontal polarization component at the position of each pixel constituting the tomographic image, and the tomographic signals A _H and A _V. Is calculated by Equation 2.

リターデーション画像を生成することにより、本実施形態では網膜層中における複屈折性のある層を把握することが可能となる。

By generating a retardation image, in the present embodiment, it is possible to grasp a birefringent layer in the retinal layer.

<DOPU image generation>
Image generating unit 191, the acquired tomographic signals A _H, the phase difference ΔΦ between them and A _V, to calculate the Stokes vector S by Equation 3 for each pixel.

ただし、位相差ΔΦは２つの断層画像を計算する際に得られる各信号の位相Φ_Ｈ、Φ_ＶからΔΦ＝Φ_Ｖ−Φ_Ｈとして計算する。
次に各Ｂスキャン画像を概ね測定光の主走査方向に７０μｍ、深度方向に１８μｍ程度の大きさのウィンドウを設定する。その後、各ウィンドウ内において式４で画素毎に計算されたストークスベクトルの各要素を平均し、当該ウィンドウ内の偏光の均一性ＤＯＰＵ（Ｄｅｇｒｅｅ Ｏｆ Ｐｏｌａｒｉｚａｔｉｏｎ Ｕｎｉｆｏｒｍｉｔｙ）を式４により計算する。

However, the phase difference ΔΦ is calculated as ΔΦ = Φ _V −Φ _H from the phases Φ _H and Φ _{V of} each signal obtained when calculating two tomographic images.
Next, a window having a size of about 70 μm in the main scanning direction of the measurement light and about 18 μm in the depth direction is set for each B-scan image. Thereafter, each element of the Stokes vector calculated for each pixel in Expression 4 in each window is averaged, and polarization uniformity DOPU (Degree Of Polarization Uniformity) in the window is calculated by Expression 4.

ただし、Ｑ_ｍ、Ｕ_ｍ、Ｖ_ｍは各ウィンドウ内のストークスベクトルの要素Ｑ，Ｕ，Ｖを平均した値である。この処理をＢスキャン画像内の全てのウィンドウに対して行うことで、ＤＯＰＵ画像（偏光の均一度を示す断層画像とも言う）が生成される。

However, Q _m , U _m , and V _m are values obtained by averaging the Stokes vector elements Q, U, and V in each window. By performing this process for all windows in the B-scan image, a DOPU image (also referred to as a tomographic image indicating the degree of polarization uniformity) is generated.

DOPU is a numerical value representing the uniformity of polarization, and is a numerical value close to 1 at a position where the polarization is maintained, and is a numerical value smaller than 1 at a position where the polarization is not maintained. In the structure in the retina, the RPE has a property of canceling the polarization state. Therefore, the value of the portion corresponding to the RPE in the DOPU image is smaller than that in other regions.
In the present specification, the above-described tomographic image, retardation image, DOPU image and the like corresponding to the first and second polarized light are also referred to as a tomographic image indicating a polarization state.

  As described above, in PS-OCT, polarization parameters are imaged by acquiring or generating tomographic images of P wave and S wave which are two orthogonally polarized lights. For this reason, it is necessary that the positions of the P-wave tomographic image (P-wave tomographic image) and the S-wave tomographic image (S-wave tomographic image) substantially coincide.

  On the other hand, in order to avoid the occurrence of noise due to cross coupling of the polarization maintaining fiber in the OCT imaging range, in the optical coherence tomography apparatus of this embodiment, the length of the polarization maintaining fiber is at least about 10 m. I already mentioned that length is needed.

  The above-described PS-OCT unit 100 has a main optical system housed in a casing called an exterior unit, and constitutes an apparatus. The exterior portion does not need to accommodate all the components such as the optical system described above. In the present embodiment, at least the fiber coupler 104, the configuration disposed in the optical path of the reference light including this, and the optical path of the measurement light are disposed. It suffices to store a part of the configuration. Therefore, the exterior portion can be grasped as the first storage means.

Here, the polarization-maintaining fiber 105 as the second light guide unit and the polarization-maintaining fiber 117 as the first light guide unit disposed in the apparatus, that is, inside the exterior portion, are respectively connected to the surrounding atmosphere. Consider a case where devices are placed in different locations at different temperatures. In this case, there is a difference in fiber length between the polarization maintaining fiber 105 and the polarization maintaining fiber 117 by the temperature difference in each arrangement. For example, when the fiber length is 10 m and the linear expansion coefficient of quartz glass is 0.5 × 10 ⁻⁶ , if the temperature difference is 10 degrees, the difference in fiber length is 50 μm. The polarization-maintaining fiber has birefringence with different refractive indexes on the slow axis and the fast axis. If the change in optical path length between the slow axis and the fast axis due to the change in birefringence due to temperature is 30% of the fiber length, an optical path difference between the slow axis and the fast axis will be 15 μm. The relative position of the S-wave tomographic image is also shifted by the same amount.

  FIG. 2 schematically shows a relative positional shift between the P-wave tomographic image and the S-wave tomographic image. The horizontal axis represents the distance in the depth direction (z) of the tomographic image, and the vertical axis represents the intensity of the tomographic signal. In FIG. 2, the P-wave tomographic image and the S-wave tomographic image are shifted by ΔZ relatively in the depth direction.

  The value δ of each pixel in the retardation image is obtained by quantifying the phase difference between the vertical polarization component and the horizontal polarization component at the position of each pixel constituting the tomographic image, and converting the intensity ratio into an angle. is there. Therefore, the relative positional shift between the P-wave tomographic image and the S-wave tomographic image causes the retardation image to deteriorate.

  In order to prevent such deterioration of the retardation image, it is desirable that the difference in the change in the fiber length between the polarization maintaining fiber 105 and the polarization maintaining fiber 117 caused by the temperature change in the apparatus is as small as possible. . For this purpose, the polarization-maintaining fiber 105 and the polarization-maintaining fiber 117 are covered with a member other than the exterior portion, and a storage means (a first exterior portion is formed on the exterior portion) that forms a substantially closed space separated from the space inside the exterior portion. When the first storage means is used, it is preferably stored in the second storage means). By controlling the temperature of the internal space of the storage means, the temperature difference in the space where the polarization maintaining fiber 105 and the polarization maintaining fiber 117 are placed can be suppressed. Thereby, the difference of the fiber length resulting from the difference of the temperature change in these fibers can be made small. In the present embodiment, the case where the second storage unit does not store the fiber coupler 104 corresponding to the light splitting unit or the multiplexing unit is illustrated, but the second storage unit stores the fiber coupler 104. It is also possible to adopt a form.

FIG. 3 shows an example of the storage means in this embodiment. The polarization maintaining fiber 105 and the polarization maintaining fiber 117 are wound around the same fiber holding member 301. The method of fixing or holding the fiber is not limited to the mode of winding around the member as shown in FIG. 3, but may be a mode of being arranged on a circle and being pressed and held by another member, or another holding mode. In the present embodiment, a sealing member 300 that houses the wound polarization maintaining fiber in a substantially closed space is further disposed. The sealing member 300 is disposed as the same and single accommodation means that covers the outside of the polarization maintaining fiber 105 and the polarization maintaining fiber 117.
That is, the sealing member 300 accommodates the polarization maintaining fiber 105 and the polarization maintaining fiber 117 in the same space. Here, in this example, both fibers are accommodated in the same space. However, if the temperature of the internal gas can be maintained uniformly, the fibers are divided into two partially communicating spaces. May be arranged. In this case, the space formed by the sealing member 300 is referred to as substantially the same space. The fiber sealing member 300 is provided with an inlet opening for drawing the polarization maintaining fiber into the substantially sealed space and an outlet opening for drawing it out. These openings may be set larger than the fiber diameter in order not to damage the fiber or to enable bending or the like. However, since the gap between the fiber generated in the opening and the periphery of the opening of the sealing member has such a size that the influence on the temperature in the space can be ignored, the space is referred to as a closed space in the present invention.

  According to this embodiment, the temperature of the space in which the polarization maintaining fiber is stored is made substantially uniform by storing the polarization maintaining fiber in the closed space. In this case, it is preferable that the storage means for storing these polarization maintaining fibers in a substantially closed space is composed of a member having low thermal conductivity having a function of blocking heat transfer with the external space. Furthermore, a temperature detection means for detecting the internal temperature of the enclosed space and a temperature control means for controlling the internal temperature by cooling or heating according to the detected temperature are arranged for the storage means. Is preferred.

  Further, a fan (not shown) as a temperature control means may be arranged on the wall surface of the sealing member 300 in order to adjust the temperature in the sealing member 300 as a storage means. In this case, the temperature at the time of adjustment at the factory is stored in a storage means such as a memory in the optical coherence tomography apparatus or in the control apparatus. At this time, the internal temperature of the enclosed space may be set to the temperature at the time of factory adjustment based on the temperature of the assumed actual usage environment. The temperature can be set, for example, in a state where the sealing member 300 or the like is disposed in a thermostatic chamber that can change the temperature of the bath. When the apparatus is actually installed in a hospital or the like and the subject's eye is photographed, the temperature in the sealing member 300 is detected by a temperature sensor so that the temperature becomes a desired temperature stored in the apparatus. A temperature control means such as a fan is driven. From the viewpoint of temperature control, the storage means preferably stores the polarization maintaining fiber in a sealed space. However, if the polarization maintaining fiber can be temperature-controlled, it needs to be sealed. Absent.

  Here, as a temperature sensor which is a temperature detection means, a thermocouple etc. can be used, for example. In addition to the fan, for example, a heater, a Peltier element, or the like can be used as the temperature control means. Moreover, it is good also as an aspect which controls the temperature of the fiber holding member 301 which is not the aspect which controls the temperature of the space in the sealing member 300 but the polarization | polarized-light maintaining fiber is wound and closely_contact | adhered. In this case, the temperature sensor may be configured to measure the temperature of the fiber holding member 301. Further, the fiber holding member 301 has a reel shape around which the fiber is wound. However, the fiber holding member 301 is not limited to this reel shape as long as the fiber can be held in a fixed form while being in close contact with the fiber. For example, the temperature control means may be provided in the fiber holding member so that the fiber holding member is in close contact with or in contact with the fiber to hold it and directly manages the temperature of the fiber in a state through the contacting portion. .

  Next, a modification of the present embodiment is shown in FIG. In this example, each of the polarization maintaining fiber 105 and the polarization maintaining fiber 117 is wound around a different fiber holding member 303 and fiber holding member 304 that have a reel shape and are arranged close to each other. The wound polarization maintaining fiber 105 and the polarization maintaining fiber 117 are further provided with a sealing member 302 that is the same storage means so as to cover the outside. Further, the sealing member 302 is provided with an extraction portion (not shown) configured such that a part of the wall surface can be opened and closed, so that the polarization maintaining fiber can be extracted from the sealing member 302 while being wound around the reel. It is configured. This makes it easy to replace parts due to fiber damage or the like.

  Next, another modification of this embodiment is shown in FIG. In this example, the polarization-maintaining fiber 105 is wound around a fiber holding member 306, and a sealing member 305 serving as a storage unit is disposed so as to cover the outside (FIG. 5A). Further, the polarization maintaining fiber 117 is wound around the fiber holding member 308, and a sealing member 307, which is a storage means different from the sealing member 305, is disposed so as to cover the outside (FIG. 5B). By storing each polarization-maintaining fiber in a different sealing member, the difference in fiber length due to temperature change can be suppressed to a small value.

  Here, the sealing member 305 and the sealing member 307 may be arranged in a state of being substantially close to each other as shown in FIG. By arranging them in close proximity, the temperature difference in the separate sealing members can be kept small. In the present embodiment, storage means that constitutes a closed space is disposed inside the exterior portion, and the polarization maintaining fiber is disposed inside the storage means. However, if the internal temperature of the internal space of the exterior part or the temperature of the space in which the polarization maintaining fiber is arranged can be managed, the storage means does not have to constitute the closed space. In other words, if the polarization maintaining fiber can be held in a temperature stable space and the flow of air current between the region where the temperature changes rapidly and the space can be cut off, it functions as a storage means. obtain. In the case where both polarization maintaining fibers are arranged inside such a storage means, these fibers are arranged at the same location in the storage means in order to suppress the occurrence of a temperature difference between these fibers. It is preferable. In this case, it is impossible in principle to place two fibers at the same location, and the same location described here means a place where the temperature around the fiber can be easily maintained, and grasps it as almost the same location. It is preferred that

  Further, a temperature sensor (not shown) that is a temperature detection means, a fan (not shown) that is a temperature control means, or the like may be disposed on one or both of the sealing member 305 and the sealing member 307. By controlling the temperature in the sealing member as described above, the temperature difference in the separate sealing members can be kept small.

  Next, a method for reducing the influence of the temperature change in the apparatus by correcting the length change caused by the temperature of the polarization maintaining fiber 105 and the polarization maintaining fiber 117 will be described.

  First, the polarization maintaining fiber 105 and the polarization maintaining fiber 117 are accommodated in a substantially closed space by the sealing member 300 in this embodiment, as in the example shown in FIG. Here, in order to detect the temperature inside the sealing member 300, a temperature sensor (not shown) as temperature detecting means is arranged. The temperature sensor is preferably arranged to measure the temperature in the space where the polarization maintaining fiber is placed, but instead of this, the temperature of the sealing member 300 or the temperature of the member 301 is measured to measure the polarization. A mode in which the temperature of the holding fiber is estimated may be used. By adding such a configuration, the temperature of the space inside the sealing member can be detected in real time by the temperature sensor.

In the above, a method for obtaining a suitable tomographic image by managing the temperature of the fiber has been described. Next, a method for actually correcting by using a temperature sensor in consideration of the influence of the temperature change of the fiber at the time of image generation will be described.
When assembling an optical coherence tomography apparatus in a factory, a correction process for the optical coherence tomography apparatus is often provided as a final process before inspection to perform device correction for driving operation. In the case of the present embodiment, in this correction process, the accommodation environment for the polarization maintaining fiber is corrected together with the apparatus correction using a temperature sensor. In the actual correction process, a reflection mirror is installed at the position of the eye to be examined, and a P-wave tomographic image and an S-wave tomographic image are acquired or generated. If the apparatus is correctly adjusted in the assembly process, the positions of the acquired P-wave tomographic image and S-wave tomographic image are the same. However, as described above, if the temperature in the apparatus, more specifically, the temperature in the accommodation environment of the polarization maintaining fiber changes from the time of adjustment of the assembly process, the relative position of the tomographic image may be shifted.

  As a countermeasure, the correspondence is acquired in advance as the correlation between the relative displacement amount of the tomographic image and the value of the temperature sensor obtained from the storage environment. As an acquisition method, for example, the apparatus is placed in the above-described thermostat, and the relationship between the value of the temperature sensor and the relative positional shift amount between the P-wave tomographic image and the S-wave tomographic image is changed while changing the temperature in the thermostat. Remember me inside. FIG. 7 schematically shows an example of the relationship between the relative positional shift amount of the P-wave tomographic image and the S-wave tomographic image with respect to the temperature. In the figure, the horizontal axis represents temperature, and the vertical axis represents the amount of relative position shift. The temperature at the time of adjustment in the assembly process is T0, and the apparatus is adjusted so that the relative positional deviation amount ΔZ becomes small at this time.

  As schematically shown in FIG. 7, when the temperature T decreases from T0 to T1 or increases from T0 to T2, the relative position shift amount ΔZ changes. The value of ΔZ at each temperature is stored in the optical coherence tomography apparatus in a predetermined temperature range of the assumed use environment. The signal processing unit 190 generates a relational expression between the temperature and the relative position shift amount from each value stored in the apparatus, stores the relational expression, and then ends the correction process. Here, the relational expression can be obtained by, for example, polynomial fitting by the least square method.

  On the other hand, when the apparatus is actually installed in a hospital or the like and the subject's eye is photographed, the temperature in the sealing member 300 in which the polarization maintaining fiber is accommodated is detected by a temperature sensor. The signal processing unit 190 calculates the relative displacement amount from the relational expression between the temperature and the relative displacement amount generated in the factory correction process, and stores the relative displacement amount in the apparatus. Thereafter, when the subject's eye is photographed and a P-wave tomographic image and an S-wave tomographic image are acquired, the display positions of the images, that is, the tomographic images, are corrected by the stored relative positional deviation amount. Even when a temperature change occurs in the apparatus due to these corrections, the relative positions of the P-wave tomographic image and the S-wave tomographic image become correct, and a desired tomographic image can be acquired.

  Next, as a modification, an image correction method when the polarization maintaining fiber 105 and the polarization maintaining fiber 117 are arranged in separate sealing members 305 and 307 as shown in FIG. 5 will be described. The sealing member 305 and the sealing member 307 are each provided with a temperature sensor (not shown) which is a temperature detecting means for detecting the internal temperature. The temperature sensor can detect the temperature of the space inside the sealing member 305 and the temperature of the space inside the sealing member 307 in real time. Here, as in the previous example, for example, an optical coherence tomography apparatus is placed in a thermostat, and the values of each temperature sensor, the P-wave tomogram, and the S-wave tomogram are changed while changing the temperature in the thermostat. The relationship with the relative position shift amount is stored in advance in the optical coherence tomography apparatus. At this time, it is preferable that the temperature inside the separate sealing member 305 and the sealing member 307 is individually changed, and the value of the relative positional deviation with respect to each temperature difference is stored in the optical coherence tomography apparatus.

  The signal processing unit 190 generates and stores a relational expression between the temperature difference and the relative position shift amount from each stored value. When the apparatus is actually installed in a hospital or the like and the eye to be inspected is imaged, the temperature of each of the sealing member 305 and the sealing member 307 in which each polarization maintaining fiber is stored is detected by a temperature sensor. The signal processing unit 190 calculates the relative positional deviation amount from the relational expression between the temperature difference generated in the correction process at the factory and the relative positional deviation amount, and stores this relative amount in the optical coherence tomography apparatus. Thereafter, when the eye to be examined is photographed and a P-wave tomographic image and an S-wave tomographic image are acquired, the image is corrected by the stored relative positional deviation amount.

  Here, in the above-described correction step, the temperature inside the separate sealing member 305 and the sealing member 307 may be individually changed, and the value of the relative positional deviation amount for each combination of temperatures may be stored in the apparatus as a table. . In this case, when an optical coherence tomography apparatus is actually installed in a hospital or the like and the subject's eye is imaged, the temperature inside the sealing member 305 and the sealing member 307 is detected by the above-described temperature sensor, which is a derivation means. A signal processing unit (not shown) calculates a relative positional deviation amount from a table of combinations of temperatures and relative positional deviation amounts, and stores them in the optical coherence tomography apparatus. Thereafter, when the eye to be examined is photographed to obtain a P-wave tomographic image and an S-wave tomographic image, the display positions of the images are corrected by the stored relative positional deviation amount. The image correction such as the display position of the image is executed by the image analysis unit 192 functioning as an image correction unit.

  As a result, even when a temperature change occurs in the apparatus, the relative display position shift amount between the P-wave tomographic image and the S-wave tomographic image can be reduced by suppressing the influence of the temperature difference between the polarization maintaining fibers. Can be suppressed.

  As mentioned above, although preferable embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. For example, in this embodiment, the interference signal is obtained using the Michelson interferometer method, but the same effect can be obtained even when the Mach-Zehnder interferometer method is used.

  In this embodiment, a fiber optical system using a fiber coupler is used as a light splitting unit having a polarization maintaining function. However, instead of this, a spatial optical system using a collimator lens and a polarization beam splitter may be used as the light dividing means.

  In this embodiment, an example using an SD-OCT optical coherence tomography apparatus using a low-coherent light source and a grating is shown, but an SS-OCT system using a wavelength swept light source is also used. Good.

(Other embodiments)
The present invention also includes an operation method of the apparatus for performing the above-described correction operation when the apparatus is installed or when the apparatus is movable in the optical coherence tomography apparatus having the configuration shown in the above-described embodiment. Contains. The present invention supplies a program that realizes each process defined in this control method to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program It can also be implemented as a process to perform. It can also be implemented by a circuit (for example, ASIC) that realizes one or more functions.

  In the above-described embodiment, the present invention describes the case where the subject is an eye. However, the present invention can also be applied to a subject such as a skin or an organ other than the eye. 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 an optical coherence tomography apparatus exemplified by an ophthalmologic apparatus, and the eye to be examined is grasped as one aspect of the subject.

Claims (22)

Detection means for detecting combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
A first optical fiber disposed in the optical path of the reference light and guiding the reference light;
A second optical fiber disposed in the optical path of the measurement light and the return light to guide the measurement light and the return light;
First storage means for storing the detection means;
An optical coherence tomography apparatus comprising: a second storage unit that stores the first optical fiber and the second optical fiber, the second storage unit being different from the first storage unit.   The optical coherence tomography apparatus according to claim 1, wherein the second storage unit stores the first optical fiber and the second optical fiber in substantially the same space.   The first optical fiber and the second optical fiber each have a length of 10 m or more and are housed in the second housing means while being wound around the same member. Item 3. The optical coherence tomography apparatus according to Item 1 or 2.   The first optical fiber and the second optical fiber each have a length of 10 m or more, and are housed in the second housing means while being wound around different members. Item 3. The optical coherence tomography apparatus according to Item 1 or 2.   The members around which the first optical fiber and the second optical fiber are wound can be taken out from the second storage means in a state where the first optical fiber and the second optical fiber are wound. The optical coherence tomography apparatus according to claim 4, wherein:   2. The light according to claim 1, wherein there are a plurality of the second storage units, and the first optical fiber and the second optical fiber are stored in different second storage units. Coherence tomography equipment.   The optical coherence tomography apparatus according to claim 6, wherein the different second storage units are arranged inside the first storage unit. A temperature detection means arranged in each of the different second storage means for detecting the internal temperature of the internal space of the second storage means;
The relative position shift amount of each of the plurality of tomographic images generated based on the lights of different polarizations obtained by dividing the combined light, and the detected internal temperature of each of the second storage means Storage means for storing the correspondence relationship of
The image correction means for correcting a shift amount of a relative position of the plurality of tomographic images according to the correspondence relationship stored in advance and the detected internal temperature. Or the optical coherence tomography apparatus of 7.   The said 2nd accommodating means has a temperature control means which controls so that the temperature inside these 2nd accommodating means may become the same, The any one of Claim 6 thru | or 8 characterized by the above-mentioned. Optical coherence tomography system. Detection means for detecting combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
A first optical fiber disposed in the optical path of the reference light and guiding the reference light;
A second optical fiber disposed in the optical path of the measurement light and the return light to guide the measurement light and the return light;
Storage means for storing the detection means,
The optical coherence tomography apparatus, wherein the first optical fiber and the second optical fiber are disposed at substantially the same location inside the storage means.   The optical coherence tomography apparatus according to claim 10, further comprising a second storage unit that is disposed in the storage unit and stores the first optical fiber and the second optical fiber.   The optical coherence tomography apparatus according to claim 10 or 11, further comprising a member around which the first optical fiber and the second optical fiber are wound.   The optical coherence tomography apparatus according to claim 10, wherein the first optical fiber and the second optical fiber have different members wound around each other.   11. The optical coherence tomography according to claim 10, further comprising two different second storage units disposed in the storage unit and configured to store the first optical fiber and the second optical fiber, respectively. apparatus. Detection means for detecting lights of different polarizations obtained by dividing the combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
A first optical fiber disposed in the optical path of the reference light and guiding the reference light;
A second optical fiber disposed in the optical path of the measurement light and the return light to guide the measurement light and the return light;
Storage means for storing the detection means, the first optical fiber, and the second optical fiber;
An optical coherence tomography apparatus comprising: temperature control means for controlling temperatures of the first optical fiber and the second optical fiber held inside the storage means. Inside the housing means, holding means capable of controlling the temperature and holding the first optical fiber and the second optical fiber in contact with each other,
16. The temperature control means controls the temperature of the first optical fiber and the second optical fiber through the contacting portion by controlling the temperature of the holding means. The optical coherence tomography apparatus described in 1. The detection means detects different polarized lights obtained by dividing the combined light,
The optical coherence tomography according to any one of claims 1 to 16, further comprising image generation means for generating a tomographic image of the subject based on the detected lights of different polarizations. apparatus. Detection means for detecting lights of different polarizations obtained by dividing the combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
Image generating means for generating a plurality of tomographic images based on the detected lights of different polarizations;
When the plurality of tomographic images are generated, the temperature of the first optical fiber that is arranged in the optical path of the reference light and guides the reference light, and the optical path of the measurement light and the return light are arranged in the optical path. Temperature detecting means for detecting the temperature of the second optical fiber that guides the measurement light and the return light; and
Corresponding relationship between the temperature of the first optical fiber stored in advance, the temperature of the second optical fiber, and the shift amount of each relative position of the plurality of tomographic images, and the detected first light Image correction means for correcting a shift amount of the relative position of each of the generated tomographic images based on the temperature of the fiber and the detected temperature of the second optical fiber. Optical coherence tomography system.   The optical coherence tomography apparatus according to any one of claims 1 to 18, wherein the first optical fiber and the second optical fiber are polarization maintaining fibers. A step of detecting light of mutually different polarizations obtained by dividing the combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light; and
A first optical fiber disposed in the optical path of the reference light and guiding the reference light; and a second optical fiber disposed in the optical path of the measurement light and the return light to guide the measurement light and the return light. A step of controlling the temperature of the first optical fiber and the second optical fiber held inside the storage means together with the detection means;
Generating a plurality of tomographic images based on the detected lights of different polarizations;
A method of operating an optical coherence tomography apparatus, comprising: Detecting light of mutually different polarizations obtained by dividing the combined light obtained by combining the return light from the subject irradiated with the measurement light and the reference light corresponding to the measurement light;
Generating a plurality of tomographic images based on the detected different polarizations;
When the plurality of tomographic images are generated, the temperature of the first optical fiber that is arranged in the optical path of the reference light and guides the reference light, and the optical path of the measurement light and the return light are arranged in the optical path. Detecting the temperature of the second optical fiber that guides the measurement light and the return light; and
Corresponding relationship between the temperature of the first optical fiber stored in advance, the temperature of the second optical fiber, and the shift amount of each relative position of the plurality of tomographic images, and the detected first light Correcting the amount of relative positional deviation of each of the generated tomographic images based on the temperature of the fiber and the detected temperature of the second optical fiber. Operation method of tomography apparatus.   A program causing a computer to execute each step of the operation method of the optical coherence tomography apparatus according to claim 20 or 21.

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