Optical coherence tomography apparatus, optical coherence tomography system, optical coherence tomography method, and inspection method

Abstract

Provided is an optical coherence tomography apparatus or the like capable of performing tomography over a wide range at once and also capable of performing tomography of a distant object. The optical coherence tomography apparatus comprises an objective lens condensing light from a light source onto a sample and performs tomography of the sample on the basis of interference of sample light, which is reflected light from the sample, and reference light, which is reflected light from a reference surface provided between the objective lens and the sample, wherein both the sample light and the reference light pass through the objective lens, the sample is irradiated at a wide angle with the light from the light source that has passed through the objective lens, and the reference surface is configured of a light scatterer.

Description

[Technical Field]

[0001] The present disclosure relates to an optical coherence tomography apparatus, an optical coherence tomography system, an optical coherence tomography method, and an inspection method. [Background technology]

[0002] Optical coherence tomography (OCT) is primarily used in the medical field for tomography of biological organs such as the eyeball.

[0003] Known optical coherence tomography devices include those that split light from a light source using a beam splitter or the like, irradiate the split light onto a sample and a reference mirror separately to obtain reflected light, and perform tomography using the interference of these reflected lights that have passed through separate optical paths (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-104127 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide an optical coherence tomography device capable of performing tomographic imaging of a wide area at once and of performing tomographic imaging of a remotely located object, as well as an optical coherence tomography system, an optical coherence tomography method, and an inspection method using the same. [Means for solving the problem]

[0006] The present disclosure provides an objective lens that focuses light from a light source onto a sample; An optical coherence tomography apparatus for performing tomography of the sample based on interference between sample light, which is light reflected from the sample, and reference light, which is light reflected from a reference surface provided between the objective lens and the sample, Both the sample light and the reference light pass through the objective lens; The light from the light source that has passed through the objective lens is irradiated onto the sample at a wide angle, The reference surface is made of a light scattering medium. This invention relates to an optical coherence tomography apparatus.

[0007] The objective lens is preferably a short focal length lens or a wide angle lens.

[0008] It is also preferable that the focal position of the objective lens is variable.

[0009] It is also preferable that the light scatterer has a haze value of 5 to 95% in a wavelength range of 400 to 1750 nm.

[0010] It is also preferable that the light-scattering body has a total light transmittance of 10 to 90% in the wavelength range of 400 to 1750 nm.

[0011] It is also preferred that the reference surface is a plane.

[0012] The optical coherence tomography apparatus preferably includes a probe having the objective lens.

[0013] The optical coherence tomography apparatus preferably includes a plurality of the probes.

[0014] It is also preferable to obtain information based on light of different frequencies from a plurality of the above-mentioned probes.

[0015] It is also preferable that the probe is arranged so as to be mechanically movable.

[0016] The present disclosure also relates to an optical coherence tomography system including the optical coherence tomography apparatus and a movement mechanism that mechanically moves the probe included in the optical coherence tomography apparatus.

[0017] The present disclosure also relates to an optical coherence tomography method using the optical coherence tomography apparatus or the optical coherence tomography system.

[0018] It is preferable to perform tomography with the distance between the objective lens and the sample being 2 cm or more and less than 2 m.

[0019] It is also preferable to perform tomography while mechanically moving the probe having the objective lens.

[0020] It is also preferable to perform tomography while mechanically moving the sample.

[0021] It is also preferable to use a plurality of probes each having the above objective lens to perform tomography using light of a plurality of different frequencies.

[0022] It is also preferable to use a plurality of probes each having the above objective lens to perform tomography from a plurality of different directions.

[0023] The present disclosure also relates to an inspection method for inspecting the internal state of a sample based on image data obtained by performing tomographic imaging of the sample using the optical coherence tomography method. [Effects of the Invention]

[0024] According to the present disclosure, it is possible to provide an optical coherence tomography device capable of performing tomographic imaging of a wide area at once and of performing tomographic imaging of an object located at a distance, as well as an optical coherence tomography system, an optical coherence tomography method, and an inspection method using the same. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing an example of a conventional optical coherence tomography (OCT) device. [Figure 2] 1 is a schematic diagram illustrating an example of an OCT device according to the present disclosure. [Figure 3] FIG. 10 is a schematic diagram showing another example of an OCT device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0026] In the medical field, optical coherence tomography (OCT) devices using a Michelson interferometer as shown in Fig. 1 are commonly used. In the OCT device 10 of Fig. 1, light output from a light source 11 is split by a coupler 12 to generate reference light that passes through an optical path including a circulator 13 and a reference mirror 14, and sample light that passes through an optical path including a circulator 15 and a sample 16. The reference light and sample light are combined by a coupler 17, and an interference signal is detected by a photodetector 18.

[0027] OCT devices used in the medical field are focused on taking high-precision tomographic images of extremely small areas, such as the eyeball, from close up, and have the problem that they are difficult to apply to fields that require taking tomographic images of wide areas at once or of objects located far away.

[0028] After extensive research, the inventors discovered that the above problems can be solved by configuring an OCT device in which both sample light and reference light pass through an objective lens so that light from a light source that has passed through the objective lens is irradiated onto the sample at a wide angle, and by configuring the reference surface using a light scatterer, and have thus completed the OCT device disclosed herein.

[0029] The present disclosure will be specifically described below.

[0030] The present disclosure provides an OCT device that includes an objective lens that focuses light from a light source onto a sample, and performs tomographic imaging of the sample based on the interference between sample light, which is light reflected from the sample, and reference light, which is light reflected from a reference surface provided between the objective lens and the sample, wherein both the sample light and the reference light pass through the objective lens, and light from the light source that has passed through the objective lens is irradiated onto the sample at a wide angle, and the reference surface is composed of a light scatterer.

[0031] In the OCT device of the present disclosure, both sample light, which is light reflected from the sample to be imaged, and reference light, which is light reflected from the reference surface, pass through the objective lens. With this configuration, even when a part (e.g., a probe) including the objective lens is used in a location away from the main body (housing), there is no difference in the environment (temperature, etc.) between the sample light path and the reference light path, so the deviation of the obtained tomographic image is small. The sample light and reference light are incident on the sample side of the objective lens and exit to the light source side.

[0032] The sample light and reference light are generated from light from a light source. The light from the light source passes through an objective lens included in the OCT device of the present disclosure and is focused on the sample. The light reflected from the sample becomes the sample light. Furthermore, a portion of the light from the light source is reflected by a reference surface provided between the objective lens and the sample and becomes the reference light. It is preferable that both the sample light and the reference light are generated from light from the light source that has passed through the objective lens. Compared to a conventional Michelson-type OCT device in which the sample light and the reference light are generated separately from light that has been split before passing through the objective lens, the difference in the environments of the sample light path and the reference light path can be reduced, and the deviation of the obtained tomographic image can be further reduced.

[0033] In the OCT device of the present disclosure, the light from the light source that passes through the objective lens is irradiated onto the sample at a wide angle. This configuration allows tomography of a wide area at once, and also enables tomography of a target at a distance.

[0034] "Wide-angle irradiation" means irradiation in a range in which the angle α between the light beam incident on the sample surface and the normal to the sample surface is 0 degrees or more and 90 degrees or less. The angle α may be more than 0 degrees, preferably 1 degree or more, and more preferably 2 degrees or more, or may be less than 90 degrees, preferably 30 degrees or less, and more preferably 15 degrees or less. The irradiation may be performed over the entire range described above.

[0035] Examples of methods for irradiating at a wide angle include (i) a method in which light from the light source is converged using a short focal length lens as an objective lens, and the resulting convergent light is deflected at a wide angle using a scanning mirror and irradiated onto the sample, or (ii) a method in which light from the light source is irradiated onto the sample using a wide-angle lens as an objective lens. Method (i) is particularly preferable. Method (i) allows the objective lens (short focal length lens) to be placed before the scanning mirror, i.e., on the optical path between the light source and the scanning mirror, which increases the degree of freedom in adjusting the angle at which light is irradiated onto the sample and the distance to the sample.

[0036] In the method (i), the inclination of the mirror surface of the scanning mirror is changed so that the angle α falls within the range described above, thereby enabling the light from the light source to be irradiated onto the sample at a wide angle.

[0037] In the method (ii), the sample can be irradiated with light from the light source at a wide angle by irradiating the sample with a configuration in which the angle of view θ determined by the following method is 0 degrees or more and 90 degrees or less. The angle of view θ may be greater than 0 degrees, preferably greater than 1 degree, and more preferably greater than 2 degrees, and may be less than 90 degrees, preferably less than 30 degrees, and more preferably less than 15 degrees. The angle of view θ is calculated from the value of tan θ below when both diagonal ends of the image sensor provided in the OCT device are connected to the center of the lens. tanθ = "Half the distance between both ends of the image sensor" ÷ "Distance from the center of the lens to the image sensor" The imaging element may be provided in a detector (detector (1)) described later, and may be a CCD image sensor or an InGaAs photodiode.

[0038] Within the above-mentioned wide-angle illumination range, it is preferable that the incident light beam sufficiently reaches the corners of the range that the objective lens can capture, and that optical performance can be ensured within this range. It is also preferable that deviations in optical imaging, such as chromatic aberration and distortion, be 10% or less relative to the central focused position.

[0039] The objective lens is preferably a short focal length lens or a wide angle lens.

[0040] The short focal length lens is a focusing lens having a focal length of 50 mm or less when focused at infinity using light with a wavelength of 800 to 1750 nm. The focal length of the short focal length lens is more preferably 45 mm or less, and is preferably 1 mm or more, and more preferably 2 mm or more. The focal length can be measured according to JIS B 7094 (ISO 517).

[0041] The short focal length lens preferably has a variable focal position (light collection distance), which allows the focal position to be changed without replacing the objective lens. An example of a short focal length lens with a variable focal position is a collimator lens that allows adjustment of the distance between the lens and the exit of an optical fiber.

[0042] It is also preferable that the short focal length lens has a variable focal length, which allows the focal length to be changed without replacing the objective lens.

[0043] The short focal length lens may be a collimating lens such as an achromatic fiber collimator.

[0044] The short focal length lens can be particularly suitably used in the method (i) above.

[0045] The wide-angle lens may have a focal length of 200 mm or less, preferably 100 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, when focused at infinity using light with a wavelength of 800 to 1750 nm, and may have a focal length of 1 mm or more, preferably 2 mm or more, and even more preferably 8 mm or more. The focal length can be measured according to JIS B 7094 (ISO 517).

[0046] The wide-angle lens preferably has a variable focal position (light-collecting distance), which allows the focal position to be changed without replacing the objective lens.

[0047] It is also preferable that the wide-angle lens has a variable focal length, which allows the focal length to be changed without changing the objective lens.

[0048] The wide-angle lens may be a wide-angle camera lens.

[0049] The wide-angle lens can be particularly suitably used in the method (ii) above.

[0050] The reference surface is provided between the objective lens and the sample, and may be provided perpendicular to the optical axis of the objective lens, but is not limited to this. The reference surface is required to be a surface that reflects at least a portion of the light from the light source, and is preferably a surface that transmits and reflects a portion of the light from the light source, in that it is easy to configure the sample light and the reference light to pass through a common optical path. In this aspect, the light that has transmitted through the reference surface is focused on the sample to generate sample light, while the light that has been reflected by the reference surface becomes reference light.

[0051] The reference surface is preferably a flat surface, more preferably a flat surface of a reference member, and even more preferably a surface of the reference member facing the sample. The reference member preferably transmits a portion of the light from the light source and reflects a portion of the light.

[0052] The reference surface may be made of a light scattering medium, and the reference member may also be made of a light scattering medium. When the light from the light source that has passed through the objective lens is irradiated onto the sample at a wide angle, the light from the light source may be incident obliquely onto the reference surface depending on the position. When the light is incident obliquely onto the reference surface, it is not easy to obtain reflected light with sufficient intensity along the same optical path as the incident light. In the OCT device of the present disclosure, by configuring the reference surface with a light scatterer, it is possible to easily obtain reflected light along the same optical path as the incident light from light incident at an angle to the reference surface, thereby enabling tomographic imaging of a wide area at once, and also of a target at a distance.

[0053] The light-scattering body may have a haze value of 5 to 95% in the wavelength range of 400 to 1750 nm. The haze value is preferably 10% or more, more preferably 15% or more, and is preferably 90% or less, more preferably 80% or less. The haze value can be measured using a haze meter in accordance with JIS R 3106 (ISO 9050), JIS K 7361-1 (ISO 13468-1), and JIS K 7136 (ISO 14782).

[0054] The light-scattering body may have a total light transmittance of 10 to 90% in the wavelength range of 400 to 1750 nm, and the total light transmittance is preferably 15% or more, more preferably 20% or more, and is preferably 80% or less, more preferably 70% or less. The total light transmittance can be measured using a haze meter in accordance with JIS R 3106 (ISO 9050), JIS K 7361-1 (ISO 13468-1), and JIS K 7136 (ISO 14782).

[0055] The light scatterer may be any material that scatters light from the light source, such as glass or resin with fine irregularities on the surface, such as ground glass, frosted glass, or a Fresnel lens; or glass or resin containing light-scattering bubbles, particles, or the like inside. As the light scattering material, glass or resin having fine irregularities on the surface is particularly preferred.

[0056] The reference member may have any shape having a flat surface, such as a plate, a cylinder, or a prism, but is preferably cylindrical. If the reference member has a cylindrical shape, it does not necessarily have to be a perfect cylinder. Furthermore, if the reference member has a flat surface other than the reference surface, the reference surface and the other flat surface do not necessarily have to be parallel to each other.

[0057] The thickness of the reference member (thickness in the optical axis direction) is preferably, for example, 0.01 to 50 mm, more preferably 0.1 mm or more, even more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more, and more preferably 30 mm or less, even more preferably 20 mm or less, and particularly preferably 10 mm or less. When the thickness of the reference member is not constant, it is preferable that the thickness of both the thinnest part and the thickest part be within the above range.

[0058] The reference member preferably satisfies the following relational expression (1). nd≧Z max (1) (wherein nd represents the optical thickness of the reference member, and Z max represents the measurable distance.) The optical thickness is the product of the refractive index and the actual (geometric) thickness of the reference member. The measurable distance is expressed by the following relational expression (2). Z max =c / (4δf) (2) (where c is the speed of light, and δf is the frequency interval for sampling the OCT interference signal.) When a reference member that satisfies the relation (1) is used, the signal based on the back reflection from the rear base surface (the surface opposite to the reference surface) of the reference member is included in the tomographic image (depth greater than 0, Z max Since the image does not appear within the range corresponding to less than 1000 nm, a tomographic image with higher accuracy can be obtained.

[0059] It is more preferable that the reference member satisfies the following relational expression (3). n×WD>nd>n×Z max (3) (where n represents the refractive index of the reference member. WD represents the working distance of the OCT device. nd and Z max is as above.) The working distance is the distance from the front surface of the objective lens on the sample side to the sample when the lens is in focus. By using a reference member that satisfies relational expression (3), the intensity of the ghost image due to back reflection from the rear base surface (the surface opposite the reference surface) of the reference member can be reduced, thereby enabling to obtain a tomographic image with even higher accuracy. In order to further reduce the intensity of the ghost image due to the back reflection, it is preferable that the thickness of the reference member is large within the range that satisfies the relation (3). It is also preferable that the rear base surface of the reference member is inclined with respect to the reference surface. The above-mentioned effect becomes particularly noticeable when an anti-aliasing filter (low-pass filter) described later is provided.

[0060] It is particularly preferable that the reference member satisfies the following relational expression (4). nd=m×Z max (4) (Wherein, nd and Z max is as above. m represents an integer of 1 or greater.) m is preferably an integer of 1 or more and 20 or less, and also preferably an integer of 1 or more and 10 or less. When a reference member satisfying the relation (4) is used, a signal based on back reflection from the rear base surface (the surface opposite to the reference surface) of the reference member is detected at the end of the tomographic image (depth 0 or Z max Since the image overlaps the position corresponding to the position of the tomographic image, the influence on the tomographic image is small, and a tomographic image with higher accuracy can be obtained.

[0061] The reference surface may be positioned at a distance of 5 mm to 5 m from the objective lens, which distance is preferably 10 mm or more, more preferably 20 mm or more, and is preferably 2 m or less, more preferably 1 m or less.

[0062] The OCT device of the present disclosure may be equipped with the above-mentioned reference surface (reference member).

[0063] The light source may be a low-coherence light source, and is preferably a frequency scanning light source that changes and scans the frequency (wavelength) over time. The above-mentioned frequency scanning light source can be a wavelength swept laser using a wavelength sweep filter (driven by a polygon mirror, driven by a galvanometer mirror, etc.), an FDML laser, a MEMS wavelength swept light source (MEMS VCSEL, external cavity MEMS Fabry-Perot laser, etc.), an SGDBR laser, etc.

[0064] The light beam output from the light source may be visible light or infrared light, with near-infrared light (NIR) being preferred. The light beam preferably has a wavelength of 800 to 2000 nm. From the standpoint of light source stability and sensor reliability, light beams with central wavelengths of 940±50 nm, 1100±50 nm, 1310±50, 1550±100, or 1750±100 nm are particularly preferred.

[0065] The OCT device of the present disclosure may include the above light source.

[0066] The OCT device of the present disclosure performs tomography of the sample based on interference between the sample light and the reference light. In principle, the interference may be any interference that allows both the sample light and the reference light to pass through the objective lens, but Fizeau interference or Mirau interference is preferred, and Fizeau interference is more preferred.

[0067] Examples of types of OCT that can be used in the OCT device of the present disclosure include time domain OCT (TD-OCT) and Fourier domain OCT (FD-OCT). Examples of FD-OCT include spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). Among these, SS-OCT is preferred due to its high sensitivity and large measurable depth.

[0068] The OCT device of the present disclosure preferably includes a probe having the objective lens. The number of the probes may be one or more.

[0069] The probe may or may not have the reference surface (or reference member), but preferably has the reference surface (or reference member).More preferably, the probe further has a collimator and a scanning mirror, which will be described later.

[0070] When the OCT device of the present disclosure includes a plurality of the above-described probes, the plurality of probes can perform tomography at different positions in parallel. Furthermore, when a plurality of the probes are provided, information based on light of different frequencies may be acquired from the plurality of probes. With this configuration, the plurality of probes can perform tomography at different depths in parallel.

[0071] The probe may be arranged to be mechanically movable. With this configuration, tomography can be performed while mechanically moving the probe, making it easy to perform tomography of a large sample. The direction of movement of the probe is not particularly limited and may be determined depending on the range to be photographed tomographically, but may be, for example, a direction intersecting the optical axis of the objective lens, a direction intersecting the optical path of the light beam emitted from the objective lens toward the sample, a direction following the shape of the sample, a direction following the sample surface, or a direction approximately parallel to the sample surface. The above configuration can be realized, for example, by arranging the probe on a moving mechanism to be described later.

[0072] The probe is preferably connected to the OCT device main body (housing) via an optical fiber. In this embodiment, the light from the light source, as well as the sample light and reference light, are transmitted through the optical fiber. In the above embodiment, even if the imaging target is located far from the OCT device main body, adjusting the length of the optical fiber allows the probe to be positioned near the imaging target and tomographic imaging to be performed. Since the light from the light source, the sample light, and the reference light are all transmitted through the optical fiber, even if the optical fiber is lengthened, there is no difference in the environment between the sample light path and the reference light path, and the deviation in the resulting tomographic image is small. Furthermore, because it is a wired type using the optical fiber, high-resolution OCT measurement can be performed even on an imaging target located far from the main body.

[0073] The length of the optical fiber is not particularly limited and can be determined depending on the location of the subject to be photographed, but may be, for example, 1 m or more, preferably 3 m or more, more preferably 5 m or more, and even more preferably 10 m or more, or may be 100 m or less, or may be 50 m or less.

[0074] The OCT device main body (housing) preferably includes, for example, the light source, and more preferably includes a circulator, a detector, a DAQ device, an arithmetic device, and the like, which will be described later.

[0075] The OCT device of the present disclosure preferably further includes a collimator that converts the light from the light source into parallel light, and the collimator is preferably provided on the optical path between the light source and the reference surface, and more preferably on the optical path between the light source and the objective lens. The above-mentioned objective lens (preferably a short focal length lens) can also be used as the collimator.

[0076] The OCT device of the present disclosure preferably further includes a scanning mirror that scans the light from the light source that is focused on the sample. The scanning mirror is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the collimator and the objective lens. This aspect is particularly suitable when the objective lens is a wide-angle lens. It is also preferable that the scanning mirror is provided on the optical path between the objective lens and the reference surface, which is particularly suitable when the objective lens is a short focal length lens.

[0077] Examples of the scanning mirror include a galvanometer mirror, a polygon mirror, an MEMS mirror, etc. Among these, a galvanometer mirror is preferred, a one-axis or two-axis galvanometer mirror is more preferred, and a two-axis galvanometer mirror is even more preferred.

[0078] The OCT device of the present disclosure preferably further includes a driving device for driving the scanning mirror.

[0079] The OCT device of the present disclosure preferably further includes a circulator that outputs light from the light source to the objective lens and outputs the sample light and reference light that have passed through the objective lens to a detector that detects the sample light and reference light. In this embodiment, the sample light and reference light can be transmitted by a single circulator. This configuration allows for a more compact device and reduced costs compared to a device that uses separate circulators for the sample light and reference light, as shown in FIG. 1.

[0080] The circulator preferably has three or more ports, and more preferably has three ports.

[0081] The circulator is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the light source and the collimator. In the case of a three-port circulator, the light from the light source is input from a first port on the light source side and output from a second port on the objective lens side, and the sample light and reference light that have passed through the objective lens are input from the second port and output from a third port on the detector side.

[0082] The OCT device of the present disclosure preferably further includes a detector (also referred to as detector (1)) that detects the sample light and reference light. The detector (1) preferably detects an interference signal due to the sample light and reference light. The detector (1) may be one or more.

[0083] The detector (1) is preferably a differential photodetector. The detector (1) may have a function of amplifying the signal. Alternatively, a separate amplifier may be provided.

[0084] The OCT device of the present disclosure preferably further includes a coupler (also referred to as coupler (1)) that splits the light from the light source into split light 1 used to generate the sample light and reference light, and split light 2 used to remove the DC component of the interference signal. The coupler (1) is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the light source and the circulator.

[0085] When the coupler (1) is provided, the intensity ratio of the split light 1 to the split light 2 is preferably 90:10 to 99:1, and more preferably 92:8 to 98:2. By dividing the light into such an intensity ratio, the DC component can be effectively removed from the interference signal.

[0086] The OCT device of the present disclosure preferably further includes a detector (also referred to as detector (2)) that detects the split light 2. Detector (2) may be the same detector as detector (1) described above, or may be a different detector.

[0087] The OCT device of the present disclosure preferably further includes an attenuator that attenuates the split light 2. The attenuator is preferably a variable optical attenuator (VOA). The attenuator is preferably provided on the optical path between the coupler (1) and a detector (2) that detects the split light 2.

[0088] The OCT device of the present disclosure may further include a polarization module that adjusts the polarization state of the light from the light source. The polarization module is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the light source and the coupler (1).

[0089] When the OCT device of the present disclosure includes a plurality of the probes, it preferably includes a coupler (also referred to as coupler (2)) that splits the light from the light source into light to be sent to each probe. The coupler (2) is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the circulator and the collimator.

[0090] The OCT device of the present disclosure may include a modulator that modulates the frequency of light. By applying optical modulation using the modulator, the depth displayed as a tomographic image can be freely changed. The modulators include acousto-optic (AO) modulators and electro-optic (EO) modulators. When a plurality of the probes are provided, a plurality of the modulators may be provided corresponding to the respective probes. With this configuration, information based on light of different frequencies can be acquired from the plurality of probes, and tomographic imaging at different depths can be performed in parallel using the plurality of probes. Images corresponding to different depths obtained by the plurality of probes can be encoded in the depth direction and simultaneously displayed on a display device described below. The modulator is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the circulator and the collimator.

[0091] When the OCT device of the present disclosure includes a plurality of the above-described probes, it is preferable to include a coupler (also referred to as coupler (3)) that combines the light from the plurality of probes. By providing coupler (3), the number of DAQ devices described below can be reduced. The coupler (2) described above can also be used as the coupler (3). The coupler (3) is preferably provided on the optical path between the light source and the objective lens, and more preferably on the optical path between the circulator and the collimator.

[0092] The OCT device of the present disclosure preferably further includes a data acquisition (DAQ) device that collects interference signals due to the sample light and the reference light. The DAQ device preferably includes an A / D converter. The DAQ device preferably converts the collected interference signals into digital data. The number of the DAQ devices may be one or more. When a plurality of the probes is provided, it is preferable to provide a plurality of the DAQ devices corresponding to the respective probes in order to reduce the calculation load.

[0093] The OCT device of the present disclosure further includes a function for determining the measurable distance (Z max), it is preferable to provide an anti-aliasing filter (also called a low-pass filter) that attenuates unnecessary frequency components exceeding the reference frequency (f). The anti-aliasing filter is preferably provided on the optical path between the detector (1) and the DAQ device.

[0094] The OCT device of the present disclosure preferably further includes a calculation device that generates an optical coherence tomographic image based on the interference signal between the sample light and the reference light, and that generates the optical coherence tomographic image by converting the interference signal into an image according to characteristics such as intensity.

[0095] The OCT device of the present disclosure preferably further includes a display device for displaying the obtained optical coherence tomographic image. The display device may be a stationary or portable type, but a portable type is preferable because it allows the image to be confirmed at the imaging site. The connection to the computing device may be wired or wireless. The display device may be one or more.

[0096] An example of the OCT device of the present disclosure is shown in FIG. 2, but the OCT device of the present disclosure is not limited to this. In the OCT device 100 shown in Fig. 2, a frequency scanning light source 101 outputs light used for OCT. The frequency scanning light source 101 outputs a trigger signal at the start of each frequency scan. The light is detected by a Mach-Zehnder interferometer, and a K clock signal is output for sampling at equal frequency intervals. The light output from the frequency scanning light source 101 is split in a coupler 102 at an intensity ratio of 95:5 into split light 1 used to generate sample light and reference light, and split light 2 used to remove the DC component of the interference signal. Split light 1 is input to port 1 of circulator 103, output from port 2, and transmitted to probe 104 through an optical fiber several meters long. In the probe 104, the divided light 1 is converted into parallel light by a collimator 105, and then reflected by a galvanometer mirror 106 to enter an objective lens 107, which is a wide-angle lens. The galvanometer mirror 106 is driven by a galvanometer mirror driver 111 to scan the parallel light in the X and Y directions perpendicular to the optical axis. The parallel light incident on the objective lens 107 passes through a reference member 108 made of a light scatterer and is focused on a sample 110, which is the object to be imaged, and is reflected on the sample surface to enter the objective lens 107 as sample light. Furthermore, a portion of the parallel light incident on the objective lens 107 is reflected on a reference surface 109 provided on the reference member 108 and enters the objective lens 107 as reference light. The sample light and reference light incident on the objective lens 107 pass through the galvanometer mirror 106 and collimator 105, then enter port 2 of the circulator 103 through an optical fiber, exit from port 3, and then enter a differential light detection amplifier 113. The differential light detection amplifier 113 detects and amplifies an interference signal based on the interference between the sample light and the reference light. The split light 2 split by the coupler 102 is attenuated by a variable optical attenuator 112 and then input to a differential optical detection amplifier 113. The differential optical detection amplifier 113 uses the signal of the split light 2 to remove the DC component contained in the interference signal. The DC component is removed by the differential photodetector amplifier 113, and the amplified interference signal is collected and converted into digital data by a DAQ device (A / D converter) provided in the PC 114. Collection of the interference signal is started by a trigger signal emitted by the frequency scanning light source 101, and is performed in synchronization with the K clock signal. Note that there is a measurable distance (Z max ) is provided with an anti-aliasing filter (not shown) that attenuates unwanted frequency components above 100 kHz. The arithmetic unit included in the PC 114 generates an optical coherence tomographic image of the sample 110 based on the interference signal converted by the DAQ unit, and displays the image on the mobile display 115 .

[0097] Furthermore, another example of the OCT device of the present disclosure is shown in FIG. 3, but the OCT device of the present disclosure is not limited to this. 3, light emitted from an objective lens 107, which is a short focal length lens, is reflected by a galvanometer mirror 106, passes through a reference member 108, and is then irradiated onto a sample 110. By changing the tilt of the galvanometer mirror 106 with a galvanometer mirror driver 111, light can be irradiated onto the sample 110 at a wide angle. The sample light from the sample surface is reflected by the galvanometer mirror 106 and enters the objective lens 107. A part of the light emitted from the objective lens 107 is reflected by a reference surface 109 provided on a reference member 108 and enters the objective lens 107 as reference light. The other configuration is as described in FIG.

[0098] In the OCT device of the present disclosure, when the probe and the OCT device main body (housing) are connected via an optical fiber having a length of 3 m or more, and the temperature difference between the atmosphere surrounding the probe equipped with the objective lens and the atmosphere surrounding the OCT device main body (housing) is 1°C or more, it is preferable that the deviation of the obtained optical coherence tomographic image is 100 μm or less. In industrial fields, etc., the subject to be imaged may be located far away from the OCT device body, outdoors, or in a facility with high or low temperatures. In such cases, there is a large difference in the environment (temperature) between the probe and the OCT device body. Therefore, in an OCT device in which the sample optical path is on the probe side and the reference optical path is on the body side, a large deviation occurs in the obtained tomographic image due to the difference in the environment between the sample optical path and the reference optical path. In contrast, the OCT device disclosed herein does not have a difference in the environment between the sample optical path and the reference optical path, even in such cases, so the deviation in the obtained tomographic image is small.

[0099] The length of the optical fiber in the above embodiment is preferably 3 m or more, more preferably 5 m or more, and even more preferably 10 m or more, and may be 100 m or less, or may be 50 m or less.

[0100] In the above embodiment, the temperature difference between the atmospheres is preferably 1° C. or more, more preferably 5° C. or more, and even more preferably 10° C. or more. The temperature difference is preferably 50° C. or less.

[0101] The deviation of the optical coherence tomographic image is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less. The above deviation (ΔZ) is calculated using the following formula (A): ΔZ(μm)=dn / dT(1 / ℃)×L(m)×10 6 ×2×Δt(℃) (A) (where dn / dT is the temperature coefficient of the refractive index of the optical fiber material (1 / °C), L is the length of the optical fiber (m), and Δt is the temperature difference (°C) between the sample optical path and the reference optical path.) The above ΔZ is the deviation in optical distance. When the optical fiber material is silica glass, the light wavelength is 1.3 μm, and the temperature is near room temperature, dn / dT is approximately 1.9 × 10 -5 (1 / ℃).

[0102] In an OCT device in which the sample optical path is on the probe side and the reference optical path is on the main body side, the temperature difference between the atmosphere around the probe and the atmosphere around the OCT device main body is reflected almost directly in the temperature difference Δt in the optical path, resulting in a large deviation ΔZ in the obtained tomographic image.In contrast, in the OCT device disclosed herein, even if the temperature difference between the atmosphere around the probe and the atmosphere around the OCT device main body is large, the temperature difference Δt in the optical path is extremely small, and therefore ΔZ is also extremely small.

[0103] The OCT device of the present disclosure preferably has a surface area of ​​0.1 to 100 cm in length and 0.1 to 100 cm in width that can be imaged with a resolution of 10 μm or better per tomographic imaging performed under the following conditions: This allows accurate tomographic imaging of a wide area at once (even when using other light sources). (light source) AXSUN high-speed wavelength swept light source (center wavelength: 1310 nm, sweep width: 100 nm, A-scan rate: 50 kHz, output power: 25 mW, coherence length: 12 mm) (distance between objective lens and sample) 200cm

[0104] The present disclosure also provides an OCT system including the OCT device of the present disclosure described above and a movement mechanism that mechanically moves the probe included in the OCT device. According to the OCT system of the present disclosure, tomography can be performed while mechanically moving the probe, so that tomography of a large sample can be easily performed. The direction of movement of the probe is not particularly limited and may be determined depending on the range to be photographed tomographically, but may be, for example, a direction intersecting the optical axis of the objective lens, a direction intersecting the optical path of the light beam emitted from the objective lens toward the sample, a direction following the shape of the sample, a direction following the sample surface, or a direction approximately parallel to the sample surface. The movement mechanism may be a mechanism that automatically moves the probe.

[0105] The OCT device or OCT system of the present disclosure can be used to perform optical coherence tomography of a sample. The present disclosure also provides an OCT method using the OCT device or OCT system of the present disclosure described above. The OCT method of the present disclosure makes it possible to take tomographic images of a wide area at once and to take tomographic images of a remote target. Furthermore, even when tomography is performed at a location distant from the OCT device body, there is no difference in the environment between the sample optical path and the reference optical path, so the deviation in the obtained tomographic image is small.

[0106] In the OCT method of the present disclosure, tomography can be performed with the distance between the objective lens and the sample being 2 cm or more and less than 2 m. The distance between the objective lens and the sample may be more than 3 cm, 5 cm or more, 10 cm or more, or 20 cm or more. In the OCT method of the present disclosure, the OCT device or OCT system of the present disclosure is used, so that tomography can be performed even on a sample located far away as described above.

[0107] In the OCT method of the present disclosure, tomography can be performed with the distance between the reference surface and the sample being 0 to 50 mm. The distance between the reference surface and the sample is preferably 0.01 mm or more, more preferably 0.1 mm or more, and is preferably 30 mm or less, more preferably 10 mm or less.

[0108] In the OCT method of the present disclosure, tomography may be performed while mechanically moving a probe having the objective lens. With this configuration, tomography can be performed while mechanically moving the probe, making it easy to perform tomography of a large sample. The direction of movement of the probe is not particularly limited and may be determined depending on the range to be photographed tomographically, but may be, for example, a direction intersecting the optical axis of the objective lens, a direction intersecting the optical path of the light beam emitted from the objective lens toward the sample, a direction following the shape of the sample, a direction following the sample surface, or a direction approximately parallel to the sample surface. In the above aspect, the probe may be disposed on the above-mentioned movement mechanism and moved.

[0109] In the OCT method of the present disclosure, tomography may be performed while the sample is mechanically moved. This configuration makes it possible to perform tomography of a mechanically moved sample (product, etc.) on a production line, etc. The direction of movement of the sample is not particularly limited and may be determined depending on the range to be photographed tomographically. For example, the direction may be a direction intersecting the optical axis of the objective lens, a direction intersecting the optical path of the light beam emitted from the objective lens toward the sample, a direction following the shape of the sample, a direction following the sample surface, or a direction approximately parallel to the sample surface. In the above embodiment, the probe may be fixed or may be moved during tomography.

[0110] In the OCT method of the present disclosure, a plurality of probes each having the objective lens may be used to perform tomographic imaging using light of a plurality of different frequencies. With this configuration, the plurality of probes can perform tomographic imaging at different depths in parallel. In the above aspect, information based on light of different frequencies may be obtained from the plurality of probes, and tomography may be performed based on the information.

[0111] In the OCT method of the present disclosure, a plurality of probes each having the objective lens may be used to perform tomography from a plurality of different directions. With this configuration, the plurality of probes can simultaneously perform tomography from different directions on a single sample.

[0112] The present disclosure also provides an inspection method for inspecting the internal state of a sample based on image data obtained by tomographically imaging the sample using the OCT method of the present disclosure described above. The inspection method of the present disclosure makes it possible to inspect the internal condition of a sample over a wide area at once, and to inspect the internal condition of a sample located at a distance. Furthermore, even when the examination is performed at a location away from the OCT device main body, there is no difference in the environment between the sample optical path and the reference optical path, so the deviation in the obtained tomographic image is small, allowing for high-precision examination.

[0113] The inspection may be an inspection of the sample for internal defects, such as foreign matter, voids, etc.

[0114] The OCT device, OCT system, OCT method, and inspection method of the present disclosure can be suitably used in all fields where OCT can be used. As described above, they are capable of performing tomographic imaging of a wide area at once and of imaging a remote target. Furthermore, even when tomographic imaging is performed at a location remote from the OCT device itself, the resulting tomographic images exhibit minimal deviation, making them particularly suitable for use in the industrial field. The OCT device, OCT system, OCT method, or inspection method of the present disclosure can also be incorporated into industrial product production lines.

[0115] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Explanation of symbols]

[0116] 10:OCT device 11:Light source 12, 17: Coupler 13, 15: Circulator 14: Reference mirror 16: Sample 18: Photodetector 100:OCT device 101: Frequency scanning light source 102: Coupler 103: Circulator 104: Probe 105: Collimator 106: Galvanometer mirror 107: Objective lens 108: Reference material 109:Reference plane 110: Sample 111: Galvanometer mirror driver 112: Variable optical attenuator 113: Differential photodetector amplifier 114:PC 115: Mobile Display

Claims

1. an objective lens that focuses light from a light source onto a sample; An optical coherence tomography apparatus that performs tomographic imaging of the sample based on interference between sample light, which is light reflected from the sample, and reference light, which is light reflected from a reference surface provided between the objective lens and the sample, Both the sample light and the reference light pass through the objective lens; The light from the light source that has passed through the objective lens is irradiated onto the sample at a wide angle, The reference surface is made of a light scattering medium. Optical coherence tomography device.

2. The optical coherence tomography apparatus according to claim 1 , wherein the objective lens is a short focal length lens or a wide angle lens.

3. 3. The optical coherence tomography apparatus according to claim 1, wherein the focal position of the objective lens is variable.

4. 3. The optical coherence tomography apparatus according to claim 1, wherein the light scattering medium has a haze value of 5 to 95% in a wavelength range of 400 to 1750 nm.

5. 3. The optical coherence tomography apparatus according to claim 1, wherein the light scattering medium has a total light transmittance of 10 to 90% in a wavelength range of 400 to 1750 nm.

6. The optical coherence tomography apparatus according to claim 1 or 2, wherein the reference surface is a flat surface.

7. The optical coherence tomography apparatus according to claim 1 , further comprising a probe having the objective lens.

8. The optical coherence tomography apparatus according to claim 7 , comprising a plurality of the probes.

9. The optical coherence tomography apparatus according to claim 8 , wherein information based on light of different frequencies is acquired from the plurality of probes.

10. The optical coherence tomography apparatus according to claim 7 , wherein the probe is arranged to be mechanically movable.

11. An optical coherence tomography system comprising: the optical coherence tomography apparatus according to claim 10; and a movement mechanism that mechanically moves the probe included in the optical coherence tomography apparatus.

12. An optical coherence tomography method comprising a step of performing optical coherence tomography of a sample using the optical coherence tomography apparatus according to any one of claims 1, 2, and 7 to 10, or the optical coherence tomography system according to claim 11.

13. The optical coherence tomography method according to claim 12, wherein the tomography is performed with the distance between the objective lens and the sample being 2 cm or more and less than 2 m.

14. The optical coherence tomography method according to claim 12, wherein tomography is performed while mechanically moving a probe having the objective lens.

15. The optical coherence tomography method according to claim 12, wherein the tomography is performed while the sample is mechanically moved.

16. The optical coherence tomography method according to claim 12, wherein a plurality of probes each having the objective lens are used to perform tomography using light of a plurality of different frequencies.

17. The optical coherence tomography method according to claim 12, wherein a plurality of probes each having the objective lens are used to perform tomography from a plurality of different directions.

18. An inspection method for inspecting an internal state of a sample based on image data obtained by performing tomographic imaging of the sample using the optical coherence tomography method according to claim 12.

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