WO2019035441A1 - Measurement device - Google Patents

Abstract

Provided is a measurement device which is capable of appropriately performing imaging using full-range optical coherence tomography (OCT) imaging and imaging using normal OCT, despite having a simple configuration. The present invention is provided with: a light source; a measurement optical system which guides, to an object to be examined, a line image into which measurement light from the light source is formed; a reference optical system which adjusts the optical path length of reference light from the light source; a line beam forming optical system for the reference light which is provided to the reference optical system, and which gives the reference light a linear shape; a mirror which is provided to the reference optical system, and which is capable of setting the reflection angle of the reference light; a multiplexing means which multiplexes the reference light which has passed through the reference optical system, and the measurement light which has passed through the object to be examined, to generate coherent light; and a light receiving means which receives the coherent light and generates an output signal. The signal processing of the output signal is different in cases when the mirror has a prescribed angle than in cases when the mirror is set to an angle other than the prescribed angle.

Description

Measuring device

The present invention relates to a measurement apparatus for acquiring an optical interference image of an object to be inspected.

In the field of ophthalmology, there is known a measuring apparatus which scans measurement light at the anterior segment or the fundus of an eye to be examined and examines the eye to be examined. Among them, in recent years, a device (hereinafter referred to as an OCT device) using an optical coherence tomography (OCT) capable of noninvasively observing / measuring a tomographic image of the fundus and the anterior segment has been in widespread use. In OCT, low coherent light (measurement light) is irradiated to the eye to be examined, and information on a tomographic image of the eye to be examined is obtained using interference light obtained by combining the return light from the eye to be examined and the reference light. Further, by scanning this measurement light in a predetermined range on, for example, the fundus of the eye to be examined, three-dimensional tomographic information in the predetermined range can be obtained. An OCT apparatus embodying the method is widely used in medicine from research to clinic.

OCT is roughly classified into two types, time domain OCT and Fourier domain OCT. Furthermore, Fourier domain OCT includes spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). The Fourier domain OCT uses light having a wide wavelength band, separates the obtained interference light to perform signal acquisition, and performs processing such as Fourier transformation on the acquired signal to obtain information on a tomographic image of the eye to be examined. You are getting In the SD-OCT using broadband light, the obtained interference light is spatially dispersed by a spectrometer to obtain information for each frequency. In SS-OCT using light from a wavelength-swept light source as broad-band light, interference light obtained using light of wavelengths different temporally is temporally dispersed to obtain information for each frequency.

For example, for the purpose of shortening measurement time, a line scanning Michelson-type OCT apparatus (hereinafter referred to as a line OCT apparatus) that obtains tomographic information using measurement light shaped in a linear shape instead of using spot measurement light Is introduced in Non-Patent Document 1. In the line OCT apparatus, the cross-sectional shape of light emitted from the light source is formed into a line shape using a collimator lens and a cylindrical lens, and measurement light is irradiated as a line beam on the fundus of the eye to be examined. Then, the measurement light returned from the fundus and the reference light similarly shaped in a line are combined, and the generated interference light is received by the line sensor. Conventionally, the fundus is irradiated with spot light as A scan, and information obtained by line scanning the spot light as B scan is obtained at one time as a line beam in which the spot light is lined up according to the line OCT apparatus. It can be acquired. Thereby, the acquisition time of the signal corresponding to the conventional B scan can be shortened significantly.

In OCT, there are various artifacts that have been a problem in data analysis or processing, one of which is the problem of complex conjugate artifacts. Since the interference signal is detected as a real value, complex conjugate ambiguity occurs in the depth direction profile reconstructed by Fourier transform processing. Specifically, a complex conjugate artifact appears as a mirror image of the real image on the opposite side of the real image with respect to the zero delay position where the optical path length of the measurement optical path is equal to the optical path length of the reference optical path. Overlapping of the mirror image on the real image can lead to misanalysis of the OCT data. This complex conjugate artifact is likely to occur when trying to obtain tomographic information of a wide range of the fundus or when trying to obtain tomographic information up to a deep position of the fundus.

Non-Patent Document 1 proposes a full-range OCT imaging technique in which a phase shift method is applied to line OCT as means for removing complex conjugate artifacts. That is, a predetermined inclination is given to the wave front of the reference light formed in a line shape, and a phase shift is generated by giving equal time delays in the B scan direction (reference light extension direction). The interference signal obtained in this state is subjected to Fourier transform processing in the spatial direction of B scan instead of the normal A scan direction, and the signal is analyzed to obtain a complex conjugate interference signal. It is disclosed that a tomographic image from which a complex conjugate artifact has been removed can be obtained by setting the acquired complex conjugate interference signal to a zero value and performing normal Fourier transform processing on the remaining signal.

However, by setting the complex conjugate interference signal to a zero value in this way, the data actually used for image formation is reduced to 1⁄2, and the lateral resolution is degraded. That is, in the full-range OCT imaging technology proposed in Non-Patent Document 1, good image depth and lateral resolution are not compatible. However, in actual diagnosis of the eye to be examined, it is preferable that tomographic information up to the wide range or deep position mentioned above and tomographic information from which an image with high lateral resolution is obtained although the wide range or depth position is not necessary can be acquired appropriately. Be That is, means for switching the observation method on a case-by-case basis is desired, for example, a case where it is desired to observe a locally narrow area of the subject's eye in detail or a case where an overall structure is roughly observed in a wide area.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a measurement apparatus capable of appropriately performing imaging with a full-range OCT imaging technology and imaging with a normal OCT even with a simple configuration.

In order to solve the above-mentioned subject, a measuring device concerning one mode of the present invention,
Light source,
A measurement optical system for guiding a line image obtained by shaping the measurement light from the light source to an object to be inspected;
A reference optical system for adjusting an optical path length of reference light from the light source;
A reference beam line beam forming optical system provided in the reference optical system for forming the shape of the reference light in a line shape;
A mirror provided in the reference optical system and capable of setting a reflection angle of the reference light;
Combining means for combining the reference light passing through the reference optical system and the measurement light passing through the inspection object to generate interference light;
Light receiving means for receiving the interference light and generating an output signal;
The signal processing of the output signal is different depending on whether the mirror has a predetermined angle or an angle other than the predetermined angle.

According to the present invention, even with a simple configuration, imaging by full-range OCT imaging technology and imaging by normal OCT can be appropriately performed.

It is a schematic block diagram for demonstrating the optical system of the line OCT apparatus which concerns on the 1st Example of this invention. It is a block diagram for demonstrating the control part of the line OCT apparatus which concerns on the 1st Example of this invention. It is a schematic block diagram of the line beam formation optical system for reference lights, a wave-front inclination mirror, and the relay lens system for reference lights in the reference optical system shown in FIG. It is a schematic block diagram of the line beam formation optical system for reference lights, a wave-front inclination mirror, and the relay lens system for reference lights in the reference optical system shown in FIG. It is a figure which illustrates a tomogram usually obtained and a tomogram obtained by phase shift. It is a figure for demonstrating isolation | separation of frequency distribution. It is a figure for demonstrating the change of the inclination of a tomogram accompanying fine adjustment of the inclination of a reference light wave front. It is a figure for demonstrating isolation | separation of frequency distribution accompanying fine adjustment of the inclination of a reference light wave front. It is a schematic block diagram of the line image formation optical system in a reference optical system for demonstrating control of the defocus of a reference light wave front, a wave-front inclination mirror, and the relay lens system for a reference. It is a figure for demonstrating the change of the curvature of the tomogram accompanying control of the defocus of a reference light wave front. It is a figure for demonstrating isolation | separation of frequency distribution accompanying control of defocus of a reference light wave front. It is a figure for demonstrating the change of the tomogram accompanying control of the inclination of a reference light wave front, and defocus. It is a figure for demonstrating the user interface screen of the control application which concerns on a 1st Example. It is a figure for demonstrating the user interface screen of the control application which concerns on a 1st Example. It is a schematic block diagram for demonstrating the optical system of the line OCT apparatus which concerns on the 2nd Example of this invention.

Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions of components, etc. described in the following embodiments are arbitrary, and can be changed according to the configuration of the apparatus to which the present invention is applied or various conditions. Also, in the drawings, like reference numerals are used to indicate identical or functionally similar elements.

First Embodiment
In the following embodiments, a line OCT apparatus will be described as an example of a measurement apparatus to which the present invention is applied. FIG. 1 to be referred to is a schematic configuration view for explaining an optical system of the line OCT apparatus, and FIG. 2 is a block diagram showing an entire configuration of the line OCT apparatus for explaining a control unit of the line OCT apparatus. Note that the line OCT apparatus shown in this embodiment has a Mach-Zehnder interference system. However, the present invention may be configured to use a Michelson-type interference system.

The OCT optical system in the line OCT apparatus according to the present embodiment includes a light source 001, a coupler 002, a line beam forming optical system 101, a sample optical system (measurement optical system) 102, a reference optical system 103, a beam splitter 025, and a light receiving optical system. Having 104. The light emitted from the wavelength sweepable light source 001 (SS light source) is guided to a coupler (optical coupler) 002 by an optical fiber, and is divided into measurement light and reference light by the coupler 002 with a desired division ratio. The measurement light is guided to the line beam forming optical system 101, and the reference light is guided to the reference optical system 103 through an optical fiber. The light from the light source 001 is guided by an optical fiber and split by the coupler 002, but may be guided as spatial light and split by a beam splitter or the like.

(Line beam forming optical system)
The line beam forming optical system 101 has a collimator lens 003, a cylindrical lens 004, and a lens 005 in order from the coupler 002 side. The measurement light split by the coupler 002 is guided to the line beam forming optical system 101, and is collimated by the collimator lens 003. The collimated light is further shaped by the cylindrical lens 004 and the lens 005 into a line beam whose cross-sectional shape is a line on the virtual plane 006. In the figure, a solid line indicates a light beam condensed on the virtual plane 006 in the sagittal direction perpendicular to the paper, and a broken line indicates a light beam collimated on the virtual plane 006 in the tangential direction parallel to the paper. .

(Sample optical system)
The measurement light passes through the beam splitter 025 and is guided to the sample optical system 102. The sample optical system 102 includes, in order from the beam splitter 025 side, a focus lens 007, an aperture 008, a galvanometric mirror 009, a lens 010, and an objective lens 011. The galvanometric mirror 009 is disposed at a position substantially conjugate with the anterior segment of the subject eye 012, and the angle with respect to the optical axis is variable. The lens 010 and the objective lens 011 form an objective lens system, and guide measurement light to the eye 012 to irradiate a line beam onto the fundus.

The focus lens 007 is movable on the optical axis by a focus drive unit 0081 described later. The position on the optical axis of the focus lens 007 is controlled such that the virtual plane 006 and the fundus of the eye 012 are optically conjugate. Further, the measurement light (line beam) irradiated onto the fundus is scanned on the fundus in the state of a line beam by rotational driving of the galvanometric mirror 009. The measurement light reflected and scattered by the fundus of the eye to be inspected 012 is transmitted back to the above-described optical element in the sample optical system 102 as return light, and then reaches the beam splitter 025. The return light reflected by the beam splitter 025 is guided to the light receiving optical system 104, and forms linear measurement light (return light) on a virtual plane 026 described later.

(Light receiving optical system)
In the light receiving optical system 104, a virtual plane 026 located in the vicinity of the exit surface of the beam splitter 025 is optically conjugate to the fundus of the eye 012 and the virtual plane 006. Furthermore, the virtual plane 026 is also conjugated with the light receiving surface of the line sensor 029 via the lens 027 and the lens 028. Therefore, the measurement light (return light) reflected and scattered from the irradiation position of the line beam on the fundus reaches the line sensor 029 and forms an image.

(Reference optical system)
On the other hand, the reference light split by the coupler 002 is guided to the reference optical system 103 through the optical fiber. The reference optical system 103 includes a collimator lens 014, an ND filter 015, a mirror 016, a mirror 018, a retro reflector 017, a mirror 019, a cylindrical lens 020, a lens 021, a wavefront tilt mirror 022, a lens 023, and a lens 024. These configurations are arranged in order from the exit end of the optical fiber. The reference light collimated by the collimator lens 014 passes through the ND filter 015 and is attenuated to a predetermined light amount. Thereby, adjustment of the light quantity difference of the measurement light and reference light which passed the fundus is made. Thereafter, the reference light is reflected by the mirror 016 and the mirror 018 while keeping the collimated state, is reflected by the retroreflector 017 movable in the optical axis direction, and is reflected by the mirror 018, the mirror 016 and the mirror 019 . Further, the reference light is shaped by the cylindrical lens 020 and the lens 021 to form a linear line beam as an intermediate image on the wavefront tilt mirror 022. The line beam as an intermediate image may be referred to as an intermediate line image. The cylindrical lens 020 and the lens 021 constitute a line beam forming lens system for reference light. The line-like intermediate image formed on the wavefront tilt mirror 022 passes through the beam splitter 025 through the lens 023 and the lens 024 to form a line beam of reference light on the virtual plane 026. The lens 023 and the lens 024 constitute a relay lens system for reference light. Since the virtual plane 026 is also conjugate with the light receiving surface of the line sensor 029 as described above, as a result, the intermediate line beam is in a conjugate relationship with the light receiving surface of the line sensor 029.

(Interferometric optics)
In the present embodiment, the interference optical system is constituted by the beam splitter 025. The reference light that has passed through the reference optical system 103 and the measurement light that has passed through the fundus of the subject's eye 012 via the sample optical system 102 are combined by the beam splitter 025 and each line of the reference light and measurement light is on the virtual plane 026. The beams interfere. The interfered line beam is received by the line sensor 029 through the lens 027 and the lens 028, and the obtained output signal is output from the line sensor 029.

(Polarization adjustment)
In the optical system of the line OCT apparatus described above, in the optical fiber from the coupler 002 to the reference optical system 103, a polarization adjusting paddle 013, in which the optical fibers are bound in a plurality of rings, is disposed. A polarization adjustment drive unit 0061 for driving the polarization adjustment paddle 013 is disposed in addition to the polarization adjustment paddle 013. With this configuration, the line OCT apparatus can adjust the polarization state of the reference light with respect to the polarization state of the measurement light so as to improve the interference state between the measurement light and the reference light.

(Control system)
As shown in FIG. 2, the line OCT apparatus in the present embodiment includes a sampling unit 030, a memory 031, a signal processing unit 032, a monitor 033, an operation input unit 034, and a control unit 035 in addition to the OCT optical system described above. It has a control system. The control unit 035 is configured by a general-purpose computer or the like, and is connected to the sampling unit 030, the memory 031, the signal processing unit 032, the monitor 033, and the operation input unit 034. Then, input of control signals and the like to these configurations, reception of output signals from these configurations, and the like are performed.

The operation input unit 034 is an input device for instructing the control unit 035, and is configured of, for example, a keyboard, a mouse, and the like. The monitor 033 displays various information and various images sent from the control unit 035, a mouse cursor according to the operation of the operation input unit 034, and the like. The sampling unit 030 is connected to the line sensor 029 and controls the line sensor 029 to acquire an interference signal at a predetermined timing. The memory 031 stores the acquired interference signal, position information of the galvanometric mirror 009, various information related to measurement of an image generated from the interference signal, various programs for executing the measurement, and the like. The signal processing unit 032 performs processing such as Fourier transform on the interference signal acquired by the sampling unit 030 to generate tomographic information such as luminance information and a tomographic image. Note that although the control unit 035, the monitor 033, and the like described herein are individually shown in the drawing, they may be configured integrally or partially. Further, the control unit 035 and the OCT optical system may be integrally configured.

The control unit 035 is also connected to the light source 001, the line sensor 029, the mirror drive unit 051, the polarization adjustment drive unit 0061, the reflector drive unit 0071, the focus drive unit 0081, and the galvano drive unit 0091 in addition to the configuration described above. There is. These configurations are for control of each configuration of the OCT optical system, and control of each configuration in the OCT optical system by the control unit 035 is also possible. The focus driver 0081 moves the focus lens 007 in the optical axis direction to control the position of the focus lens 007 on the optical axis. The galvano drive unit 0091 drives the galvanometric mirror 009 to scan the fundus of the line-shaped measurement light. The reflector drive unit 0071 moves the retroreflector 017 in the optical axis direction, and adjusts the optical path length difference between the optical path length of the measurement light and the optical path length of the reference light. The control unit 035 further performs light emission control of the light source 001, control of acquisition timing of an interference signal to the sampling unit 030, and the like.

(Scan control)
As described above, the output signal from the line sensor 029 is acquired by the sampling unit 030. At this time, the galvano drive angle of the galvanometric mirror 009 is controlled by the galvano drive unit 0091. The sampling unit 030 obtains this output signal for each pixel of the line sensor 0029 corresponding to one wavelength sweep of the light source 001 at an arbitrary galvano drive angle, and each pixel obtains one interference signal. Then, also at the next galvano drive angle, this output signal is acquired for each pixel of the line sensor 029 in response to one wavelength sweep of the light source 001 to obtain the next interference signal. Thereafter, interference signals are acquired one after another by this repetition. The interference signal acquired by the sampling unit 030 is stored in the memory 031 together with the galvano drive angle. The galvano drive angle is associated with the scanning position of the measurement light on the fundus. The interference signal stored in the memory 031 is frequency-analyzed by the signal processing unit 032 and associated with the position on the fundus. The tomographic image of the fundus of the eye to be examined 012 generated by the above processing is stored in the memory 031 and displayed on the monitor 033. As described above, a three-dimensional fundus volume image can be generated and displayed on the monitor 033 by acquiring information of the galvano drive angle together with the interference signal.

(Relay lens system for reference light)
FIGS. 3A and 3B illustrate in detail the cylindrical lens 020, the lens 021, the wavefront tilt mirror 022, the lens 023 and the lens 024 which are a part of the reference optical system 103 shown in FIG. An intermediate line image is formed on the wavefront tilting mirror 022 by the cylindrical lens 020 and the lens 021. In the present embodiment, the wavefront tilt mirror 022 shown in FIG. 3A is disposed in the 45-degree direction with respect to the optical axis, whereby the central axis of the reference light after reflection coincides with the optical axis of the later optical system. .

Here, the positional relationship between the lens 023 and the lens 024 will be described. Assuming that the focal length of the lens 023 is F23, the lens 023 is disposed at a distance from the wavefront tilting mirror 022 by F23. That is, the intermediate line image coincides with the front focal plane of the lens 023. At this time, a pupil image of an intermediate line image is formed on a virtual plane SP which is a back focal plane of the lens 023. That is, the light beam in the sagittal direction indicated by the solid line collimated in the intermediate line image is condensed on the virtual plane SP, while the light beam in the tangential direction indicated by the dashed line collected in the intermediate line image is the virtual plane SP It is collimated above. That is, in a state in which the line axis is rotated by 90 degrees, a pupil image of an intermediate line image is formed on the virtual plane SP.

On the other hand, when the focal length of the lens 024 is F24, the lens 024 is disposed at a distance F24 from the virtual plane SP. That is, the virtual plane SP coincides with the front focal plane of the lens 024. At this time, a line beam relayed to the intermediate line image is formed on the back focal plane of the lens 024. If F23 and F24 are equal, these line beams are equal and if different, they become line beams with a magnification corresponding to the ratio. If the entire reference optical system is arranged so that the back focal plane of the lens 024 coincides with the virtual plane 026 on which the line image of the measurement light (return light) passing through the sample optical system 102 is formed, the virtual plane 026 is obtained. The reference light and the measurement light are combined in Therefore, from the interference signal having no phase shift obtained in this state, a tomogram having no inclination is obtained as shown, for example, as a tomogram Ta1 in FIG. 4 described later.

(Slope of wavefront)
Here, in the reference light, it is necessary to tilt the wavefront for the full range processing described later. FIG. 3B shows the case where the wavefront tilt mirror 022 is given a tilt different from 45 degrees. The tilt change of the wavefront tilting mirror 022 can be controlled by the control unit 035 through a stepping motor (not shown) or the like attached to the wavefront tilting mirror 022 by the mirror driving unit 0051. When the wavefront tilt mirror 022 is given a tilt of 45 + θ / 2 degrees, the central angle of the reference light after reflection is tilted by θ. At this time, the light beam in the collimating direction is uniformly inclined by θ, and at the same time, the wavefront which is an equiphase surface of the reference light is also inclined by θ. The reference light having passed through the lens 023 forms a pupil image on the virtual plane SP, but the formation position is shifted by F23 × tan θ. Thereafter, a lens 024 forms a line beam of reference light relayed on the virtual plane 026. However, since the pupil image on the virtual plane SP is shifted by F23 × tan θ, the collimated beam directed to the virtual plane 026 is also inclined uniformly by θ ′. That is, the wavefront of the reference light on the virtual plane 026 is inclined by θ ′. Here, in the case of F23 = F24, θ ′ = − θ, and in the case of F23 ≠ F24, the relationship of θ ′ = − θ × F23 / F24 is established. Since the inclination of the wavefront inclination mirror 022 is given only in the tangential direction of one axial direction, the imaging relationship of the rays in the sagittal direction indicated by the solid line is unchanged.

Here, the intermediate line image on the wavefront tilt mirror 022 is in a conjugate relationship with the virtual plane 026 via the lens 023 and the lens 024. For this reason, the center of the reference light reflected at the optical axis center of the wavefront tilt mirror 022 reaches the optical axis of the optical system again without being shifted on the imaginary plane 026. With such a configuration, it is possible to ideally provide only a change in the wavefront of the reference light without causing, for example, vignetting due to a shift of the reference light or a decrease in light intensity distribution. The configuration of the reference light relay lens system is not limited to that shown here, and various changes may be made as long as the intermediate line image formed on the wavefront tilt mirror 022 is relayed on the virtual plane 026. It is possible.

(Full range processing)
FIG. 4 shows an example of a tomogram of the fundus of the eye to be examined 012 obtained by the signal processing unit 032. Ta1 is a tomogram acquired when the wavefront of the reference light is not inclined (angle θ). On the other hand, when the wavefront of the reference light is inclined (angle θ) by the wavefront inclination mirror 022, a tomographic image in which the whole is inclined like Tb1 is obtained. The uniform inclination of the wavefront is generally referred to as a phase shift, and causes a uniform phase delay in the B-scan direction, so that the tomographic image Tb1 has a linear depth in addition to the shape of the tomographic image Ta1. The position changes.

FIG. 5 is an example of a processing process called full range processing by the signal processing unit 032. In the full range processing, the following processing disclosed in Non-Patent Document 1 is performed. First, Fourier transform processing is performed on the interference signal from the subject eye 012 acquired by the line sensor 029 in the B-scan direction, and frequency analysis of the structure of the acquired data is performed. As a result, a separable true image (real image) and a mirror image of the frequency signal are obtained. After removing the mirror image of the frequency signal, the complex image of the original interference signal can be obtained by performing inverse Fourier transform processing on the normal image. By Fourier-transforming this complex signal in the A-scan direction in the same manner as ordinary OCT signal processing, it is possible to acquire a tomographic image from which the mirror image has been removed.

In the case of the conventional ordinary OCT signal processing, accurate tomographic information can be obtained only from an area apart from the normal image and the mirror image without overlapping each other, which limits the obtained depth information. On the other hand, in the full range processing, since the correct image separated from the mirror image is obtained even at the zero delay position, it is possible to obtain tomographic information to a deeper depth. Note that, by performing the processing described here, the horizontal resolution is reduced by half because the data corresponding to the mirror image is reduced. To cope with this, when it is intended to obtain a tomographic image excellent in resolution, the wavefront tilt mirror 022 is not given an inclination at the angle θ, and the data is acquired without tilting the wavefront of the reference light. it can.

The horizontal axis of the graph shown in FIG. 5 is frequency, and the vertical axis is intensity. The frequency distribution Sa1 indicated by a solid line is a frequency distribution when the frequency analysis is performed in a state where the wavefront of the reference light is not inclined. This corresponds to the tomographic image Ta1 in FIG. In the figure, a distribution having a peak on the + side of the frequency corresponds to a normal image, and a distribution having a peak on the − side corresponds to a mirror image. This distribution spreads across the zero frequency, and furthermore, a mirror image and an orthoimage generated in left-right symmetry overlap. In this state, separation and removal of the mirror image is not easy. In addition, it is difficult to display correct tomographic information in the region where the normal image and the mirror image overlap, so it is possible to avoid this region and to use only the tomographic information at a relatively shallow depth left.

On the other hand, the frequency distribution Sb1 indicated by a broken line is a frequency distribution when frequency analysis is performed in a state where the wavefront of the reference light is inclined. This corresponds to the tomographic image Tb1 in FIG. In this case, the two distributions are located apart from each other at the zero frequency, and further, the normal image and the mirror image are separated. Specifically, assuming that the central wavelength of the light source 001 is λ c, the wavefront tilt mirror 022 is such that, in a light beam reaching the line sensor 029, a phase difference of λ c / 4 is uniformly given between adjacent pixels of the line sensor. When the inclination angle of is set, separation of the frequency distribution becomes possible well. In such a state, the frequency distribution shown in FIG. 5 is obtained, and the mirror image frequency signal can be easily set to a zero value, and the mirror image can be removed. Therefore, acquisition of tomographic information from a wide range of wavelengths in wavelength-swept light is possible, and tomographic information from a deeper depth can be obtained.

(Fine adjustment of inclination)
Here, the size and the like of the overlapping portion between the normal image and the mirror image also depends on the size of the inclination with respect to the plane perpendicular to the optical axis of the fundus of the eye 012 to be acquired. FIG. 6 shows a tomogram acquired by giving an inclination to the wavefront of the reference light to an area with a large inclination such as the periphery of the fundus of the eye to be examined 012. A tomogram Ta2 in FIG. 6 shows a tomogram obtained when the wavefront of the reference light is inclined at a fixed value. In this example, since the original fundus structure has a large inclination, the amount of change in phase given by the inclination of the reference light wavefront is insufficient, which is sufficient for the tomographic image acquired as the sum of them. There is no inclination. FIG. 7 shows the frequency distribution corresponding to each of the tomographic images shown in FIG. 6, and the frequency distribution Sa2 corresponds to the tomographic image Ta2. The frequency distribution Sa2 partially crosses the zero frequency, and further, an orthoimage and a mirror image slightly overlap. For this reason, it is not easy to remove only the mirror image as described above.

On the other hand, the tomographic image Tb2 in FIG. 6 is a tomographic image obtained by giving a sufficient inclination to the wavefront of the reference light with reference to the inclination of the tomographic image Ta2. Specifically, with respect to the tilt given to the wavefront tilt mirror 022 as the fixed value described above, a further tilt is added by the mirror driving unit 0051 to give a larger phase shift to the wavefront of the reference light. In this example, as shown in the frequency distribution Sb2 in FIG. 7, both the normal and mirror frequency distributions do not cross the zero frequency, and the normal and mirror images are separated. In such a state, the mirror frequency signal can be easily set to a zero value, and the mirror image can be removed. That is, by suitably controlling the tilt angle of the wavefront tilt mirror 022, a tomographic image having a desired tilt can be obtained over a wide area even for the fundus of the subject eye 012 having various tilts. Becomes possible.

(Adjustment of curvature)
Here, consider an example in which the fundus has a large curvature as in the case of intense myopia. When such an eye to be examined is an object, the frequency distribution in the full range processing has a large spread. For this reason, even if a phase shift due to the inclination of the wavefront is given, it is not easy to separate mirror images well. When targeting such an eye to be examined, it can be dealt with by diverging collimated light in the reference optical system 103.

FIG. 8 is a view for explaining the appearance of the change of the wavefront in the case of diverging the collimated light of the reference optical system 103 for the purpose of coping with such an eye to be examined. In this case, it is necessary to drive the cylindrical lens 020 in the reference optical system 103 in the optical axis direction. Therefore, a cylindrical lens drive unit (not shown) for focusing and driving the cylindrical lens 020 in the optical axis direction is added to the configuration shown in FIG. Here, the cylindrical lens 020 is defocused from the initial position in the direction of the arrow by the cylindrical lens driving unit. In this case, the light beam in the tangential direction indicated by the broken line after passing through the lens 021 is not collimated but diverged. On the other hand, the defocusing effect contributes only to the component in the tangential direction, so the imaging relationship of the rays in the sagittal direction indicated by the solid line is unchanged. The cylindrical lens drive unit may be configured to be independent, for example, controlled by the control unit 35, or may be configured to be included or shared by the control unit 035 or the focus drive unit 0081.

An intermediate image is formed on the wavefront tilt mirror 022 as a diverging line beam, and the wavefront of the reference light is tilted by the reflection of the wavefront tilt mirror 022. The reflected reference light is relayed by the lens 023 and the lens 024 as a diverging line beam on the virtual plane 026. At this time, the pupil image formed by the lens 023 is on the rear side of the virtual plane SP. Accordingly, the wavefront WF formed of the equiphase surface of the divergent light beam in the tangential direction generated by the lens 024 is curved in an arc shape, and the peripheral region lags behind the central region of the light beam and reaches the virtual plane 026. That is, on the virtual plane 026, a light beam whose optical path length is longer in the peripheral region is detected. In addition, when the cylindrical lens 020 is defocused in the reverse direction, the central region is later delayed than the peripheral region on the virtual plane 026, and the reference light arrives.

FIG. 9 is a view showing an example of a tomogram acquired in a state in which the wavefront inclination mirror 022 is tilted with respect to the fundus of the subject eye 012 having a large curvature in the fundus described above. The tomographic image Ta3 is an example of a tomographic image acquired in a state where the cylindrical lens 020 is at the initial position, that is, in a state in which the reference light is collimated as usual. As shown in the figure, the tomographic image Ta3 is affected by the curvature of the fundus, and the central region is deep and the peripheral portion is shallow. That is, the tomogram Ta3 has a structure having various inclination components from the central area to the peripheral area. FIG. 10 shows the frequency distribution corresponding to each of the tomographic images shown in FIG. 9, and the frequency distribution Sa3 corresponds to the tomographic image Ta3. The frequency distribution Sa3 has a wide frequency distribution due to the influence of the structure of the fundus, and a part of the frequency distribution Sa3 crosses the zero frequency, and further, the normal image and the mirror image slightly overlap. For this reason, it is not easy to remove only the mirror image as described above.

On the other hand, the tomographic image Tb3 in FIG. 9 is a tomographic image obtained in a state in which the cylindrical lens 020 is defocused. Specifically, the cylindrical lens 020 is moved in the direction of the lens 021 in the optical axis direction by the cylindrical lens drive unit, and the wavefront indicated by WF in the drawing is given to the reference light. In the present embodiment, this process is performed with reference to the tomographic image Ta3. As shown in the figure, by defocusing the reference light, an increase in the optical path length of the peripheral region of the reference light itself offsets the shallowness of the depth of the peripheral portion of the original fundus. Therefore, the tomogram to be obtained has a structure having a component of uniform slope as a whole. In the example shown in FIG. 10, as shown in the frequency distribution Sb3, the frequency distribution is suppressed to a narrower range, does not span zero frequency, and the normal image and the mirror image are further separated. In such a state, the mirror frequency signal can be easily set to a zero value, and the mirror image can be removed. Therefore, even when the subject eye 012 having various tilt components is targeted by the curvature of the fundus, it is possible to acquire a tomogram that fits within a desired frequency distribution.

(Improved roll-off sensitivity)
The following effects can also be obtained by controlling the wavefront of the reference light by adjusting the inclination of the wavefront inclination mirror 022 and the defocus of the cylindrical lens 020. FIG. 11 exemplifies a tomogram in the case of imaging the fundus oculi peripheral region of the intensity myopic eye. In the same figure, according to the tomogram Ta4, the eye to be examined has a large curvature in its entirety for myopia intensities, and the whole is in a tilted state for a peripheral region. In such a state, the left region of the tomographic image Ta4 is at a shallow position, and the central and right regions are at a deep position. In general, there is a roll-off sensitivity characteristic as a principle characteristic of Fourier domain OCT, and the region at the upper end of the tomogram has a low frequency of an interference signal and high sensitivity can be obtained. Then, as the depth of the tomographic image becomes lower and the depth becomes deeper, the frequency of the interference signal becomes higher, the signal sampling by the sampling unit 030 acts as a low pass filter, and the sensitivity is lowered. Therefore, in the tomographic image Ta4, the left region is high in sensitivity, and the center and right regions are low in sensitivity, and an image with good sensitivity as a whole can not be obtained.

On the other hand, the tomographic image Tb4 is obtained by suitably controlling the wavefront of the reference light by adjusting the inclination of the wavefront inclination mirror 022 and the defocus of the cylindrical lens 020. As a specific adjustment, first, the wavefront inclination mirror 022 is adjusted according to the peripheral region of the subject eye 012 and the wavefront of the reference light is inclined to obtain a state in which the curvature approaches symmetrical in the left-right direction. Subsequently, the cylindrical lens 020 is moved in the direction of the optical axis to defocus, thereby flattening the entire curvature. In addition, it may be judged with reference to a tomogram, for example, based on whether or not the frequency distribution can be separated as shown in FIG. . By shaping the tomogram obtained in this manner, the frequency of the entire interference signal can be suppressed low, and an image with good sensitivity as a whole can be obtained.

As described above, by executing the focus control of the cylindrical lens 020 and the angle control of the wavefront tilting mirror 022, even when the full range processing is not applied, an effect of improving the image quality of the tomographic image can be expected. However, it should be noted that the tomogram Tb4 obtained by the above operation results in a tomogram of a shape different from normal. However, both control amounts in focus control of the cylindrical lens 020 and angle control of the wavefront tilt mirror 022 are known. Therefore, by acquiring these and performing image processing for rearranging the pixels of the image in the tomogram based on the both control amounts, an image with improved image quality is obtained with the normal shape of the tomogram Ta4. Be

(GUI)
Next, the control method of the line OCT apparatus in the present invention will be described. The line OCT apparatus has a switching function between a normal imaging mode and an imaging mode for performing full range processing (hereinafter, full range mode). That is, the operation control of the wavefront tilt mirror 022 and the cylindrical lens 020, and the processing method of the interference signal by the signal processing unit 032 are switched in conjunction with the on / off of the full lens mode. Further, the image resolution of the tomogram to be displayed is also changed according to this switching.

12A and 12B show examples of user interface screens of the control application displayed on the monitor 033. FIG. 12A shows an example of a display screen when the full range mode is off. On the monitor 033, for example, a tomographic image display unit 201a, an anterior eye observation image display unit 202, and a fundus observation image display unit 203 are disposed to display an image. In addition, for example, a focus drive control slider 204, a reference system reflector drive control slider 205, an OCT observation preview start button 206, an OCT imaging button 207, a full range mode button 208, and an angle of view switching button 209 are displayed.

The tomogram display unit 201a displays a tomogram acquired by the present OCT optical system. The anterior eye observation image display unit 202 displays an anterior eye observation image acquired by an anterior eye observation optical system (not shown) used for alignment of the subject eye 012. The fundus oculi observation image display unit 203 displays a fundus oculi observation image acquired by the fundus oculi observation optical system (not shown) used for specifying the observation region of the fundus oculi. The user uses the operation input unit 034 to input various commands to the line OCT apparatus by performing the above-described slider adjustment or button on / off operation. For example, by performing the on / off operation of the full range mode button 208, the on / off of the full range mode is switched.

A display example when the full range mode is off is shown in FIG. 12A. In this display example, since the full range mode is off, a tomographic image in which the imaging depth is within a normal narrow range is displayed on the tomographic image display unit 201a. When imaging a fundus with a large curvature like myopic myocardium under this display condition, the depth range is insufficient and the peripheral region of the tomogram is folded back and displayed as shown in the figure, which is unsuitable for wide-area observation of the fundus It becomes.

On the other hand, FIG. 12B shows a display example when the full range mode is on. When the full range mode button 208 is turned on via the operation input unit 034, the tilt angle of the wavefront tilt mirror 022 is adjusted, and a tomogram to which the full range processing is applied is acquired in the signal processing means 032. A tomogram corresponding to the full range processing is displayed on the tomogram display unit 201b of FIG. 12B. In this case, since the depth range is doubled by the full range processing, the image height of the acquired tomogram is doubled in the tomogram display unit. In addition, since the horizontal pixel resolution is halved in the process of full range processing, the image is resized twice to maintain the image width. General bilinear interpolation, bicubic interpolation or the like is used for interpolation processing for maintaining the image width at that time. As described above, by using the control unit 035 as a display control unit and automatically changing the control mode of the monitor 033, a series of complex operations related to the full range processing including the optical system can be performed by a simple user operation of only the switching button. Control can be switched in conjunction.

(Analysis function)
In the on / off switching of the full range mode, the analysis function of the control unit 035 may be interlocked and switched according to the switching so as to correspond to the feature of the tomogram obtained each time. Specifically, without full range processing, the obtained tomogram is characterized in that the depth range is narrow and the lateral resolution is fine. As a function for analyzing a relatively narrow range in detail suitable for this feature, a macular area analysis function, an optic disc analysis function, etc. can be considered. On the other hand, when full range processing is performed, the tomographic image to be obtained is characterized in that although the depth range is wide, aliasing of the tomographic image around the fundus is difficult to occur, but the lateral resolution is coarse. A function to roughly analyze a wide range suitable for this feature may be the reticular film thickness distribution analysis function, etc. The analysis including up to the periphery of the fundus may lead to early detection of diseases such as glaucoma. high. That is, when the full range mode button 208 is switched on and off, analysis modes suitable for each may be executed in conjunction.

As described above, in the first embodiment of the present invention, in the imaging of the fundus by the line OCT apparatus, the inclination angle of the wavefront tilting mirror 022 with respect to the optical axis is adjusted according to the structure of the fundus. . That is, in the case of a fundus structure that requires full range processing, a uniform phase difference is given to the wavefront of the light beam of the reference light, and full range processing is applied to the obtained interference signal to obtain a tomogram with doubled depth. It is possible to acquire. In addition, when the full range processing is unnecessary, the phase difference given to the wavefront is eliminated by adjusting the inclination angle, and it is possible to obtain a tomographic image with excellent resolution even if the depth is relatively shallow. Furthermore, the on / off switching is facilitated by interlocking the on / off switching of the optical system, the signal processing, and the analysis mode with the on / off of the full range processing by the user interface operation on the monitor screen. This makes it possible to diagnose the subject eye having various fundus structures or to acquire and analyze a tomogram according to the diagnosis.

For example, in the case of making the inclination of the wavefront of the reference light variable, it is also conceivable to realize the generation of the inclination of the wavefront only at the relative angle of the two mirrors in the reference mirror as in Non-patent Document 1. However, in such a configuration, if this relative angle is changed, not only the change of the desired inclination on the line sensor but also the shift deviation of the optical path occurs simultaneously. As one means for avoiding this, for example, a configuration may be considered in which the interference system is configured as a Mach-Zehnder type, and then the entire reference optical system is rotated using the gonio stage with the center of the line sensor as the rotation axis. However, such a response may cause the equipment to be significantly enlarged or the accuracy of the interference system to be deteriorated due to large-scale stage movement. With the configuration shown in the first embodiment described above, in the OCT using a line-shaped light flux, switching of the inclination of the reference light wavefront for increasing the photographing depth can be realized with a simple configuration. Therefore, even with a simple configuration, imaging by full-range OCT imaging technology and imaging by normal OCT can be appropriately performed.

As described above, the measurement apparatus according to this embodiment includes the light source 001, the sample optical system 102, the reference optical system 103, the beam combining means (beam splitter 025), and the light receiving means (line sensor 029). , And a signal processing unit 032. In addition, the measurement apparatus further includes a reference light line image forming optical system, a reference light relay optical system, and an inclined mirror. The sample optical system 102 shapes the measurement light obtained by dividing the light from the light source 001 as a line image and guides it to the object to be inspected (the fundus of the eye to be inspected 012). The reference optical system adjusts the optical path length of the reference light obtained by dividing the light from the light source 001 corresponding to the measurement light. The combining means combines the reference light passing through the reference optical system and the measurement light passing through the fundus to generate interference light, and the light receiving means receives the interference light to generate an output signal. The signal processing unit 032 subjects the output signal to the above-described processing such as Fourier transform, and outputs measurement information such as a tomographic image of the fundus.

The line image forming optical system for reference light is constituted of the cylindrical lens 020 and the lens 021 in the above-mentioned embodiment to form an intermediate line image of the reference light. The reference light relay optical system includes at least a first lens (lens 023) and a second lens (lens 024), and the intermediate line image and the line sensor 029 have a conjugate relationship. Further, an inclined mirror (wavefront inclined mirror 022) is disposed at the image forming position of the intermediate line image, and the reference light in a line shape is reflected and guided to a reference light relay optical system. Further, the tilt mirror can change the reflection angle of the reference light, and gives a tilt (phase shift) to the wavefront of the reference light by changing the tilt angle with respect to the optical axis.

Although the lens which comprises this relay optical system for reference lights may be comprised from single-piece | unit, you may comprise as a lens group. In this case, the reference light relay optical system is composed of a first lens group and a second lens group. Here, in the reference optical system, the intermediate line image coincides with the front focal plane of the first lens group, the optical surface of the light receiving means coincides with the rear focal plane of the second lens group, The optical system arrangement is such that the back focal plane of the lens group coincides with the front focal plane of the second lens group. These optical systems may be disposed independently of the reference optical system in the sense of adjusting the optical path length of the reference light. As described above, in the present embodiment, the light receiving means includes a line sensor. However, the line sensor is not limited as long as it has the same function.

In the embodiment described above, the measuring apparatus further includes a line beam forming optical system 101 for forming the measurement light as a line beam. The line beam forming optical system 101 is provided with line beam forming lenses having different curvatures in two meridian directions orthogonal to each other. In this embodiment, a cylindrical lens 004 is used as the line beam forming lens. In addition, the measurement apparatus further includes a dividing unit (coupler 002) that divides the light from the light source 001 into the measurement light and the reference light. Further, the reference optical system 103 forms a second line beam as a line beam generated from the reference light, and the beam splitter 025 combines the line beam and the second line beam to generate a line-like interference light. Do.

The signal processing means 032 performs the above-described full range processing of generating measurement information by removing a mirror image from a real image and a mirror image obtained by frequency analysis of an output signal from the line sensor 029. In the embodiment described above, the measurement apparatus further includes a control unit 035 that controls the reflection angle of the reference light in the tilt mirror (wavefront tilt mirror 022). The control unit 035 changes the reflection angle of the reference light of the tilt mirror depending on whether or not the full range processing in the signal processing unit 032 is performed. Further, the measuring device further includes display means (monitor 033) for displaying the measurement information. The control unit 035 changes the display mode of the measurement information by the display unit, for example, from FIG. 12A to FIG. 12B depending on whether or not the full range processing in the signal processing unit 032 is performed. Further, it is preferable that the reference beam line beam forming optical system (cylindrical lens 020 and lens 021) can be defocused by, for example, the control unit 035 or the focus driving unit 0081. Thus, appropriate measurement can be performed on the fundus of the subject eye 012 having a large curvature in the fundus. The measurement apparatus further includes a scanning unit (galvanometric mirror 009) for scanning the line image of the measurement light in a direction perpendicular to the extending direction of the line image on the test object (the fundus of the subject eye 012). . As the light source 001, a wavelength sweeping type light source for sweeping the wavelength of the light to be emitted is used.

Second Embodiment
(Change magnification)
The present embodiment differs from the above-described first embodiment in that the optical system is variable in magnification. In the OCT apparatus, it is preferable that the angle of view be switched according to the situation, for example, when it is desired to photograph the fundus at a wide angle of view or when it is desired to partially photograph at a narrow angle of view with high resolution. When imaging is performed at a wide angle of view, it is often prioritized to obtain a signal at a wider depth because a tomogram is easily folded at the periphery. On the other hand, in the case of photographing with high resolution at a narrow angle of view, finer image resolution is often prioritized. At this time, if the full range mode is switched in conjunction with the appropriate situation for each situation, the operability of the user is improved. The present embodiment addresses such a request.

FIG. 13 shows a schematic configuration diagram of an OCT optical system according to the present example. In the present embodiment, the same reference numerals are used for the same components as those described in the first embodiment, and the description thereof is omitted. Below, the configuration different from the first embodiment will be described in detail. The OCT optical system according to the present embodiment differs in that, in the sample optical system 102, an objective lens 011b is disposed, which makes the focal length of measurement light smaller than in the first embodiment.

By reducing the focal length of the objective lens, the light beam in the tangential direction indicated by the broken line of the measurement light is incident on the subject eye 012 at a large angle of view. For this reason, the fundus can be imaged at a wide angle of view in the tangential direction. On the other hand, in the sagittal direction light beam indicated by the solid line, the diameter of the beam irradiated to the pupil becomes smaller, so the focused spot on the fundus becomes larger and the lateral resolution is lowered. Conversely, when the focal length of the objective lens 011 b is long, the characteristics contrast with the characteristics described here, and a tomogram with a narrow angle of view and improved lateral resolution can be obtained.

By thus making the focal length of the objective lens 011 b variable, it is possible to control the angle of view and the lateral resolution. As a specific configuration, for example, a plurality of objective lenses 011 having large and small focal distances are built in the apparatus, and the focal distances can be made variable by replacing them by electric drive. Alternatively, the objective lens 011 may be configured separately from the apparatus main body so as to be removable, and may be replaced manually by the user. Furthermore, instead of replacement, a zoom optical system composed of a plurality of lenses may be disposed at the position of the objective lens 011 or at the position where the objective lens 011 and the lens 010 are arranged, thereby making the focal length variable. Here, although the variable part is an objective lens, the sample optical system 102 may be changed in magnification by changing the focal length of the lens 010. That is, as long as the measurement magnification in the sample optical system 102 can be arbitrarily changed, the specific configuration is not limited to the one described here.

Next, the flow of control executed in conjunction with the magnification change operation and the full range mode in the sample optical system 102 described above will be described. As shown in FIG. 12A, on the user interface screen for control application displayed on the monitor 033, a view angle switching button 209 is arranged. For example, when it is desired to image the fundus at a wide angle of view in the diagnosis of a strong myopia eye etc., a wide angle of view imaging control state (hereinafter, wide angle of view mode) is selected by user operation using the angle of view switching button 209. By this operation, the focal length of the objective lens 011 is switched by the control unit 035, and the full range mode is turned on. In accordance with this, the tilt angle of the wavefront tilt mirror 022, the defocus of the cylindrical lens 020, the processing mode of the interference signal by the signal processing unit 032, and the display image resolution of the monitor 033 are switched in conjunction. At this time, the full range mode button 208 is automatically displayed in the on state. Further, when the objective lens 011 is configured to be manually replaced by the user, by providing a detection sensor in the objective lens module, the wide field angle mode and the full range mode are automatically switched in conjunction with completion of the replacement work. It is good also as control.

That is, in the measurement apparatus according to the present embodiment, the sample optical system 102 includes an optical variable magnification system that changes the angle of view when the measurement object is irradiated to the test object (the fundus of the subject eye 012). The optical variable magnification system corresponds to, for example, a configuration in which the lens is changed from 011 to 011 b. In this case, the control unit 035 determines whether or not the above-described full range processing is performed according to the change of the angle of view of the optical magnification changing system, the reflection angle of the reference light from the wavefront tilt mirror 022, and the tomographic image of the monitor 033. Change the display style. With the above configuration, the imaging angle of view and the imaging depth are interlocked and switched according to the feature of the fundus of the eye to be examined, and a series of complex controls including the optical system are interlocked and switched by simple user operation. be able to.

(Other embodiments)
In the above-described embodiment, the fundus of the human eye (retina) is taken as an example of the object to be examined. However, the object to be examined is not limited to the fundus, and may be an anterior segment, vitreous body, or the like. Moreover, it is not limited to eyes, and skin, an organ, etc. may be sufficient. In this case, the line OCT apparatus described above can also be configured as a measurement apparatus for medical equipment such as an endoscope other than the ophthalmologic apparatus.

In addition, the present invention provides a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus execute the program. It can also be realized by a process of reading out and executing. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

Although the present invention has been described above with reference to the examples, the present invention is not limited to the examples described above. Inventions modified without departing from the spirit of the present invention and inventions equivalent to the present invention are also included in the present invention. Moreover, each Example and each modification which were mentioned above can be combined suitably in the range which does not deviate from the meaning of this invention.

This application claims priority to Japanese Patent Application No. 2017-157500 filed on Aug. 17, 2017, the contents of which are incorporated herein by reference.

101 Line Beam Forming Optical System 102 Sample Optical System (Measurement Optical System)
103 Reference optical system 104 Photography optical system 001 Light source 002 Coupler 011 Objective lens 012 Eye to be examined 022 Wave front tilt mirror 032 Signal processing unit 033 Monitor 034 Operation input unit

Claims (13)

1. Light source,
   A measurement optical system for guiding a line beam formed by measuring the measurement light from the light source to an object to be inspected;
   A reference optical system for adjusting an optical path length of reference light from the light source;
   A reference beam line beam forming optical system provided in the reference optical system for forming the shape of the reference light in a line shape;
   A mirror provided in the reference optical system and capable of setting a reflection angle of the reference light;
   Combining means for combining the reference light passing through the reference optical system and the measurement light passing through the inspection object to generate interference light;
   Light receiving means for receiving the interference light and generating an output signal;
   Equipped with
   A measuring apparatus characterized in that the signal processing of the output signal differs depending on whether the mirror has a predetermined angle or an angle other than the predetermined angle.
2. The optical system further includes a reference light relay optical system that generates a position in a conjugate relationship with the light receiving unit.
   The measuring apparatus according to claim 1, wherein the mirror is disposed at the position.
3. The reference light relay optical system includes a first lens group and a second lens group, and the conjugate relationship matches the front focal plane of the first lens group, and the rear side of the second lens group An optical system arrangement is characterized in that the light receiving surface of the light receiving means coincides with the focal plane, and the back focal plane of the first lens group coincides with the front focal plane of the second lens group. The measuring device according to claim 2.
4. The measuring apparatus according to any one of claims 1 to 3, wherein the light receiving unit includes a line sensor.
5. It further comprises a line beam forming optical system for forming the shape of the measurement light into the line shape,
   The measurement apparatus according to any one of claims 1 to 4, wherein the line beam forming optical system includes line beam forming lenses having different curvatures in two meridian directions orthogonal to each other.
6. It further comprises a dividing means for dividing the light from the light source into the measurement light and the reference light,
   After being divided by the dividing means, the line beam of the measurement light and the line beam of the reference light are formed;
   6. The light source according to claim 1, wherein the combining means combines the line beam passing through the inspection object and the line beam passing through the reference optical system to generate the line-like interference light. The measuring device according to any one of the above.
7. It further comprises signal processing means for processing the output signal and outputting tomographic information of the inspection object,
   The signal processing means is a full range for generating the tomographic information by removing a mirror image from a real image and a mirror image obtained by performing frequency analysis on the output signal when the mirror is set to an angle other than the predetermined angle. The measuring apparatus according to any one of claims 1 to 6, wherein the processing is performed.
8. And control means for controlling the reflection angle of the mirror.
   The measurement apparatus according to claim 7, wherein the control unit changes the reflection angle in accordance with whether or not the full range processing is performed in the signal processing unit.
9. It further comprises display means for displaying the tomographic information,
   9. The measurement apparatus according to claim 8, wherein the control means changes the display mode of the tomographic information by the display means in accordance with whether or not the full range process is performed in the signal processing means.
10. The measurement optical system includes an optical variable magnification system that changes an angle of view when the measurement light is irradiated to the inspection object,
    10. The measurement apparatus according to claim 9, wherein the control means changes the signal processing, the reflection angle, and the display style in accordance with a change in the angle of view of the optical magnification change system.
11. The measurement apparatus according to any one of claims 1 to 10, wherein the reference beam line beam forming optical system is capable of changing the focus position of the reference beam.
12. The measuring apparatus according to any one of claims 1 to 11, further comprising: a scanning unit configured to scan the line beam in a direction perpendicular to the extending direction of the line beam on the inspection object. .
13. The measurement apparatus according to any one of claims 1 to 12, wherein the light source is a wavelength sweeping type light source that sweeps the wavelength of light to be emitted.
    
    

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