WO2019035426A1

WO2019035426A1 - Measurement device

Info

Publication number: WO2019035426A1
Application number: PCT/JP2018/030105
Authority: WO
Inventors: 朋之池上
Original assignee: キヤノン株式会社
Priority date: 2017-08-18
Filing date: 2018-08-10
Publication date: 2019-02-21
Also published as: JP2019033956A

Abstract

Provided is a measurement device which has an inexpensive configuration, is capable of maintaining detection sensitivity, and does not require signal read time. This measurement device is provided with: a light source; a measurement optical system which shapes measurement light from the light source into a line beam, and guides said measurement light to an object to be examined; a light receiving optical system which uses a line sensor obtained by arranging pixels in a tangential direction to receive the measurement light that has passed through the object to be examined, and generates an output signal; and a signal processing means which processes the output signal and outputs measurement information about the object to be examined. In the light receiving optical system, light spots, which are obtained by forming, on the line sensor, an image of object points on the object to be examined, include light reception regions of at least two adjacent pixels in the tangential direction of the line sensor, and form an image such that entry occurs in the sagittal direction of the light reception regions of the pixels.

Description

Measuring device

The present invention relates to a measuring device that scans light on an object to be inspected to measure the object to be inspected.

In the field of ophthalmology, there is known an optical measurement device which scans measurement light at the anterior segment or the fundus of a subject's eye and examines the subject's eye. 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 formed in a line shape are combined, and the obtained 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 general, optical instruments such as line sensors have a sampling theorem, and in order to preserve the maximum spatial frequency contained in a signal, it is necessary to sample at intervals of half the spatial frequency (Nyquist frequency) or less. Therefore, with respect to the optical resolution in which a point image from the fundus of the eye to be examined as an object point is imaged as a spot image on the line sensor, it is good if the pixel spacing is not smaller than half the diameter of this spot image Spatial resolution can not be obtained. For example, in the case of using a line sensor consisting of square pixels of 10 [μm] on one side, the diameter of the spot image that can be handled is 20 [μm].

Here, in selecting a line sensor that is an important device in the line OCT apparatus, it is necessary to consider detection sensitivity. In order to enhance the light receiving efficiency of the line sensor for optimization of detection sensitivity, generally, a cylindrical lens is disposed immediately in front of the line sensor so as to condense light only in the line width direction of the line sensor. Then, it is necessary to set the imaging magnification so that the line width of the line beam of the measurement light returning from the fundus is smaller than the width of the pixel of the line sensor. That is, from the viewpoint of imaging optics, the optical resolution needs to be equal to or less than the width of the pixel. Therefore, in the case of a line sensor in which square pixels of the above-described size are arranged in a line, the beam spot diameter is preferably 10 μm or less. If the beam spot diameter is 20 μm, the width of the pixel is insufficient, the measurement light leaks from the line sensor, and the light receiving efficiency is reduced to about half.

On the other hand, the line OCT apparatus disclosed in NPLT 1 uses a sensor in which a line array of pixels of the above-described size is vertically arranged in two stages. Then, the spot beam is received by the plurality of pixels arranged in the width direction and the vertical direction, thereby satisfying the sampling theorem and the maintenance of the light reception efficiency. However, such a two-stage line sensor is expensive because of its complicated structure, and it takes time to read out a signal.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a measuring apparatus which has a more inexpensive configuration and can maintain detection sensitivity and does not require a signal readout time.

In order to solve the above-mentioned subject, a measuring device concerning one mode of the present invention,
Light source,
A measurement optical system which shapes the measurement light from the light source as a line beam and guides it to an inspection object;
A light receiving optical system that receives the measurement light having passed through the inspection object by a line sensor in which pixels are arranged in a tangential direction, and generates an output signal;
Signal processing means for processing the output signal and outputting measurement information of the inspection object;
Equipped with
In the light receiving optical system, a light spot obtained by imaging an object point on the inspection object on the line sensor is a light receiving area of at least two of the pixels adjacent to the tangential direction of the line sensor. And imaging so as to be in the sagittal direction of the light receiving area of the pixel.

According to the present invention, it is possible to provide a measuring apparatus which is more inexpensive and can maintain detection sensitivity and does not require a signal readout time.

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 the schematic for demonstrating the relationship of the spot image diameter and sensor size at the time of forming the point image in a fundus oculi on the line sensor which consists of square pixels as a light spot. It is the schematic for demonstrating the relationship of the spot image diameter and sensor size at the time of forming the point image in a fundus oculi on the line sensor which consists of square pixels as a light spot. It is the schematic for demonstrating the relationship of the spot image diameter and sensor size at the time of forming the point image in a fundus oculi on the line sensor which consists of square pixels as a light spot. It is a schematic block diagram of the relay optical system in the light reception optical system shown in FIG. It is a schematic perspective view of the relay optical system shown in FIG. 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. It is a schematic block diagram of the line beam formation optical system in a reference optical system shown in FIG. 6, a wave-front inclination mirror, and the relay lens system for reference lights. It is a schematic block diagram of the line beam formation optical system in a reference optical system shown in FIG. 6, a wave-front inclination mirror, and the relay lens system for reference lights. It is a figure which illustrates a tomogram usually obtained and a tomogram obtained by phase shift. It is a reference figure for demonstrating the full range process in a 2nd Example. It is a figure explaining the modification 1 of this invention, Comprising: It is the schematic which shows the relationship between a pixel and a light spot. It is a figure explaining the modification 2 of this invention, Comprising: It is the schematic which shows the relationship between a pixel and a light spot. It is a figure explaining the modification 2 of this invention, Comprising: It is the schematic which shows the relationship between a pixel and a light spot.

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 004, 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 011, a cylindrical lens 012 and a lens 013 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 collimated by the collimator lens 011. The collimated light is further shaped by a cylindrical lens 012 and a lens 013 into a line beam having a linear cross-sectional shape on an imaginary plane 014. In the figure, a solid line indicates a light beam condensed on the virtual plane 014 in the sagittal direction perpendicular to the paper, and a broken line indicates a light beam collimated on the virtual plane 014 in the tangential direction parallel to the paper. .

(Sample optical system)
The measurement light passes through the beam splitter 004 and is guided to the sample optical system 102. The sample optical system 102 includes, in order from the beam splitter 004 side, a focus lens 021, a stop 022, a galvanometric mirror 023, a lens 024, and a lens 025. The galvanometric mirror 023 is disposed at a position substantially conjugate to the anterior segment of the subject eye 026, and the angle with respect to the optical axis is variable. The lens 024 and the lens 025 form an objective lens system, and guide measurement light to the eye to be examined 026 to irradiate a line beam onto the fundus.

The focus lens 021 is movable on the optical axis by a focus drive unit 0081 described later. The position on the optical axis of the focus lens 021 is controlled so that the virtual plane 014 and the fundus of the eye to be examined 026 become 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 the rotational drive of the galvanometric mirror 023. The measurement light reflected and scattered by the fundus of the eye to be examined 026 reversely travels through the above-described optical element in the sample optical system 102 as return light, and then reaches the beam splitter 004. The return light reflected by the beam splitter 004 is guided to the light receiving optical system 104, and forms linear measurement light (return light) on a virtual plane 041 described later.

(Light receiving optical system)
The light receiving optical system 104 has a relay optical system and a line sensor 046. The relay optical system will be described in detail later. In the light receiving optical system 104, a virtual plane 041 located in the vicinity of the exit surface of the beam splitter 004 is optically conjugate to the fundus of the eye to be examined 026 and the virtual plane 014. Further, the virtual plane 041 is also conjugated to the light receiving surface of the line sensor 046 via the lens 042, the lens 043, the cylindrical lens 044, and the cylindrical lens 045 in the relay optical system. Therefore, the measurement light (return light) reflected and scattered from the irradiation position of the line beam on the fundus reaches the line sensor 046 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 has a collimator lens 031, an ND filter 032, a mirror 033, a mirror 034, a retroreflector 035, a cylindrical lens 036, and a lens 037 in this order from the emission end of the optical fiber. The reference light collimated by the collimator lens 031 passes through the ND filter 032 and is attenuated to a predetermined light amount. Thereby, the adjustment of the light amount difference between the measurement light passing through the fundus and the reference light is performed. Thereafter, the reference light is reflected by the mirror 033 and the mirror 034 while keeping the collimated state, is reflected by the retroreflector 035 movable in the optical axis direction, and is reflected again by the mirror 034 and the mirror 033. Further, the reference light is shaped by the cylindrical lens 036 and the lens 037, and after passing through the beam splitter 004, forms a line beam of a reference light on the virtual plane 041. The cylindrical lens 036 and the lens 037 constitute a line beam forming lens system. The retroreflector 035 is movable on the optical axis by a reflector driving unit stage 0071 described later, and adjusts the optical path length difference between the optical path length of the reference light and the optical path length of the measurement light in the sample optical system 102. Can.

(Interferometric optics)
In the present embodiment, the interference optical system is constituted by the beam splitter 004. 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 026 via the sample optical system 102 are combined by the beam splitter 004, and line beams of the reference light and the measurement light are on the virtual plane 041. have a finger in the pie. The interfered line beam is received by the line sensor 046 via a relay optical system described later, and the obtained output signal is output from the line sensor 046.

(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 003 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 003 is disposed in addition to the polarization adjustment paddle 003. 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 051, a memory 052, a signal processing unit 053, a control unit 054, a monitor 055, and an operation input unit 056 in addition to the OCT optical system described above. It has a control system. The control unit 054 is configured by a general-purpose computer or the like, and is connected to the sampling unit 051, the memory 052, the signal processing unit 053, the monitor 055, and the operation input unit 056. 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 056 is an input device for giving an instruction to the control unit 054, and is configured of, for example, a keyboard, a mouse or the like. The monitor 055 displays various information and various images sent from the control unit 054, a mouse cursor according to the operation of the operation input unit 056, and the like. The sampling unit 051 is connected to the line sensor 046 and controls the line sensor 046 to acquire an interference signal at a predetermined timing. The memory 052 stores the acquired interference signal, position information of the galvanometric mirror 023, 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 053 performs processing such as Fourier transform on the interference signal acquired by the sampling unit 051 to generate tomographic information such as luminance information and a tomographic image. Note that although the control unit 054, the monitor 055, and the like described herein are individually shown in the drawing, they may be configured integrally or partially. Further, the control unit 054 and the OCT optical system may be integrally configured.

The control unit 054 is connected to the light source 001, the line sensor 046, 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 above-described configuration. 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 054 is also possible. The focus driver 0081 moves the focus lens 021 in the optical axis direction to control the position of the focus lens 021 on the optical axis. The galvano drive unit 0091 drives the galvanometric mirror 023 to scan the fundus of the line-shaped measurement light. The reflector drive unit 0071 moves the retroreflector 035 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 054 further performs light emission control of the light source 001, control of acquisition timing of an interference signal to the sampling unit 051, and the like.

(Scan control)
As described above, the output signal from the line sensor 046 is acquired by the sampling unit 051. At this time, the galvano drive angle of the galvanometric mirror 023 is controlled by the galvano drive unit 0091. The sampling unit 051 obtains this output signal for each pixel of the line sensor 046 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 046 corresponding to the next 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 051 is stored in the memory 052 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 052 is frequency-analyzed by the signal processing unit 053 and correlated with the position on the fundus. The tomogram of the fundus of the eye to be examined 026 generated by the above processing is stored in the memory 052 and displayed on the monitor 055. As described above, a three-dimensional fundus volume image can be generated and displayed on the monitor 055 by acquiring information of the galvano drive angle together with the interference signal.

(Light receiving efficiency and resolution)
Next, an imaging magnification at the time of imaging the fundus by the line sensor 046 will be described. In imaging of the fundus oculi by the line OCT apparatus, interference light is collectively received in the pixel array direction of the line sensor. At that time, blurring occurs due to the influence of the imaging optical system. That is, a point object (object point) on the fundus surface is spread by a point spread function (PSF) to form a light spot (point image) of a finite size and form an image on the line sensor as an image. . Hereinafter, with respect to a light spot (point image) from a point object on a fundus surface in a line image of an eye to be examined obtained by the line OCT apparatus, a relationship between the light spot and pixels constituting the line sensor will be described.

FIGS. 3A to 3C are diagrams for explaining the relationship between the light spot formed on the line sensor 046 and the size of the pixels constituting the line sensor 046. FIG. Usually, in the OCT apparatus, the line sensor 046 is composed of square pixels whose width in the sagittal direction and tangential direction of the relay optical system is isotropic. 3A shows the relationship between the light spot and the pixel when priority is given to the light reception efficiency of the line sensor 046, and FIG. 3B shows the relationship between the light spot and the pixel when priority is given to the spatial frequency of the line sensor 046. There is. Further, FIG. 3C shows the relationship between the light spot and the pixel when the present invention is applied. In the figure, the light spot SP is shown as a concentric circle, and the outermost circle of the concentric circle indicates a spot defined by the half width in the PSF. Here, although the half width is used to define the outermost periphery of the light spot where the point image is spread, it may be defined by 1/10 width. Alternatively, the image of an object point may be used as a light spot as it is. Although the pixel is described here, the pixel shown in FIGS. 3A to 3C and the like is equivalent to the light receiving region in the light receiving element.

FIG. 3A shows a case where the imaging magnification is set such that the light spot SP and the width of the pixel PXa in the line sensor 046 coincide with each other. In this case, since the entire light spot SP is inside the pixel PXa, the loss of light receiving efficiency is small. On the other hand, since the width of the pixel PXa is the same as the diameter of the light spot SP, the sampling theorem is not satisfied, the spatial frequency is insufficient, and the light spot SP can not be appropriately resolved. On the other hand, FIG. 3B shows a case where the imaging magnification is set such that the width of the pixel PXb in the line sensor 046 is half the diameter of the light spot SP. In this case, the width of the pixel PXb is half of the diameter of the light spot SP, and the sampling theorem is satisfied in order to receive information obtained from the light spot SP by at least two pixels. It can be resolved properly. However, since the light spot SP protrudes above and below the pixel PXb, the loss of light receiving efficiency is large. Therefore, when the imaging magnifications of the sagittal direction and the tangential direction of a general relay optical system are isotropic, it is not possible to achieve both light receiving efficiency and resolving power.

On the other hand, in the present invention, in the relay optical system for forming the line beam formed by the virtual plane 041 on the line sensor 046, the light spot SP is connected at different magnifications in the sagittal direction and the tangential direction. It is supposed to be an image. In the example shown in FIG. 3C, the image is formed so that the width of the pixel PXb matches the diameter of the light spot in the sagittal direction, and the diameter of the light spot matches the width of eight pixels PXb in the tangential direction. , And are imaged as an elliptical light spot SP '. If such a relationship between the light spot SP 'and the pixel can be established, a loss of light receiving efficiency can be eliminated, and sufficient resolution of the light spot SP' can be achieved by receiving the light spot with eight pixels. Although an example in which the light spot is received by eight pixels is shown here, the light spot is resolved by at least two pixels adjacent in the tangential direction and in the sagittal direction in order to satisfy the sampling theorem and the light receiving efficiency. It suffices to form an image within the pixel width.

(Image transfer optical system)
Next, a configuration example for obtaining the relationship between the light spot and the pixel as illustrated in FIG. 3C will be shown. In this case, it is assumed that the light spot imaged by a line sensor obtained from an object point on a normal fundus and the size of the pixels constituting the line sensor have the relationship shown in FIG. 3B. FIG. 4 is a cross-sectional view showing the lens configuration of the relay optical system and the imaging relationship of beams in the present embodiment. 4A shows the relationship in the tangential direction corresponding to the arrangement direction of the pixels of the line sensor 046, and FIG. 4B shows the relationship in the sagittal direction corresponding to the width direction of the pixels of the line sensor 046. Indicates

The relay optical system illustrated in FIG. 4 includes a lens 042, a lens 043, a cylindrical lens 044, and a cylindrical lens 045. The relay optical system relays the line beam on the virtual plane 041 to an image plane on the line sensor 046. In the present embodiment, the cylindrical lens 044 and the cylindrical lens 045 are disposed so as to have power only in the tangential direction. However, the configuration of these cylindrical lenses and further the configuration of the relay optical system are not limited to those suitably shown here, and various modifications are possible as long as the imaging of the light spot under the conditions described above is obtained.

In this embodiment, the imaging magnification in the tangential direction is relayed so as to be 8 times larger than the imaging magnification in the sagittal direction so that sufficient resolving power can be obtained while maintaining the light reception efficiency. Set That is, assuming that the line beam is imaged at the same magnification as the fundus on the virtual plane 041, the width of the line sensor and the diameter of the light spot in the sagittal direction are made 0.5 times by the relay optical system. It is reduced and imaged. Also, in the tangential direction, the image is magnified by four times. A specific configuration for realizing this will be described below with reference to FIG.

FIG. 4A shows a cross section of an optical system which forms an image at a magnification of 4 in the tangential direction. In this optical system, only the lens 043 has power, the virtual plane 041 is an object plane, and the line sensor 046 is an image plane. Accordingly, to obtain the above imaging magnification, an object distance S43 which is a distance from the virtual plane 041 to the lens 043 and an image distance S43 ′ which is a distance from the lens 043 to the line sensor 046 (light receiving surface) is 1: It becomes a relation of four. A lens 042 is an image-side telecentric optical system, and is a field lens arranged to make a principal ray of light flux of each angle of view perpendicularly incident on the cylindrical lens, and does not affect the imaging magnification. When each chief ray is vertically incident on the cylindrical lens, the lens power received by the light flux at each angle of view becomes uniform. Furthermore, the cylindrical lens 044 and the cylindrical lens 045 do not affect the image formation because they have no power. Here, assuming that the total length of the relay optical system is L = 150 [mm], the object distance S43 is L / 5 = -30 [mm], and the image distance S43 'is 4 × L / 5 = 120 [mm]. The focal length F43 of the lens 043 is 24 [mm]. By arranging in this manner, the imaging magnification βt in the tangential direction becomes S43 ′ / S43 = −4 described above.

On the other hand, (b) in FIG. 4 shows a cross section of an optical system which forms an image at a magnification of 0.5 in the sagittal direction. In this optical system, there are three powers of the lens 043, the cylindrical lens 044 and the cylindrical lens 045. The virtual plane 041 is the object plane, and the line sensor 046 (light receiving plane) is the final image plane, and an intermediate image plane exists between them. In this case, first, as the first imaging, the first object on the virtual plane 041 is imaged as a first image on the line sensor 046 by the lens 043 in the same manner as in the tangential direction. There is no reality because this first image is affected by the power after this. The imaging magnification β1 of this first imaging is −4.

Next, as a second imaging, when the first image is regarded as a second object, the second object is imaged as a second image on an intermediate image plane SI ′ by the cylindrical lens 044 . This second image has no reality. Here, when the distance from the line sensor 046 to the intermediate image plane SI ′ is set to L ′ = 90 [mm], the second object distance S44, which is the distance from the line sensor 046 to the cylindrical lens 044, is 2 × L ′. / 3 = 60 [mm]. Then, the second image distance S44 ', which is the distance from the cylindrical lens 044 to the intermediate image plane SI', is L '/ 3 = -30 [mm], and the focal distance F44 of the cylindrical lens 044 is -20 [mm] It becomes. The imaging magnification β2 of this second imaging is S44 ′ / S44 = −0.5.

Next, as a third imaging, when the second image is regarded as a third object, the third object is a third image of the final image on the light receiving surface of the line sensor 046 by the cylindrical lens 045. Image as. This third image is formed as a real image. The distance from the intermediate image plane SI ′ to the line sensor 046 is L ′ = 90 [mm], and the third object distance S45, which is the distance from the intermediate image plane SI ′ to the cylindrical lens 045, is 4 × L ′ / 5 = It becomes -72 [mm]. Then, the third image distance S45 ′, which is the distance from the cylindrical lens 045 to the line sensor 046, is L ′ / 5 = 18 [mm], and the focal distance F45 of the cylindrical lens 045 is 14.4 [mm] . The imaging magnification β3 of this third imaging is S45 ′ / S45 = −0.25. By arranging each optical element in this manner, the first imaging magnification, the second imaging magnification, and the third imaging magnification are multiplied as the imaging magnification βs in the sagittal direction, and the above-described imaging is performed. A magnification of β1 × β2 × β3 = −0.5 is obtained.

As described above, by forming the relay optical system, it is possible to realize an optical system with anisotropic magnifications in which the tangential direction and the sagittal direction are simultaneously imaged and have different magnifications. FIG. 5 shows a perspective view of the relay optical system in the embodiment described above for reference. In the drawing, the light beams of the line beam are shown excerpted for the center and three on the left and right.

Here, in the present embodiment, it is assumed that the optical resolution on the fundus is 20 [μm], and it is 20 [μm] even on the virtual plane 041 imaged at equal magnification. By passing through the relay optical system described above, the light spot is imaged at a diameter of 20 × 0.5 = 10 μm in the sagittal direction, and sufficient imaging efficiency can be obtained. On the other hand, since an image can be formed with a diameter of 20 × 4 = 80 μm in the tangential direction and light can be received by eight pixels for one light spot, sufficient resolution can be obtained.

(Achromatic cylindrical lens)
Here, in general, in Fourier domain OCT, it is necessary to suppress chromatic aberration in all optical systems in order to use a light source having a wide wavelength band. In particular, chromatic aberration in the imaging in the sagittal direction of the relay optical system causes nonuniformity in the light receiving efficiency for each wavelength to affect the spectral shape of the interference signal, so the longitudinal resolution of the tomographic image acquired by It becomes a factor to deteriorate. Therefore, it is preferable that at least one of the cylindrical lens 044 and the cylindrical lens 045 has an achromatic structure including a cylindrical lens in which a glass with high dispersion and a glass with low dispersion are bonded. Thereby, the chromatic aberration which may be generated by the relay optical system can be suppressed.

As described above, the measurement apparatus according to the present embodiment at least includes the light source 001, the sample optical system 102, the light receiving optical system 104, and the signal processing unit 053. The sample optical system 102 shapes the measurement light from the light source 001 as a line beam and guides it to the eye 026. The light receiving optical system 104 receives measurement light passing through the eye to be examined 026 by a line sensor 046 in which the pixels PXb are arranged in the tangential direction, and generates an output signal. The signal processing unit 053 processes the output signal and outputs measurement information such as tomographic information of the eye to be examined 026. A light spot SP ′ obtained by imaging an object point on the eye to be inspected (on the inspection object) on the line sensor 046 in the light receiving optical system 104 is at least two adjacent to the line sensor 046 in the tangential direction. Includes a light receiving area of one pixel PXb. Further, in the light receiving optical system 104, the light spot SP 'is imaged so as to be in the sagittal direction of the light receiving region of the pixel XPb.

Here, as described above, the light receiving optical system 104 is imaged on an intermediate image plane (an image of a virtual plane 041) formed at a position conjugate to an object point on the optical path from the eye to be examined 026 to the line sensor 046 The relay lens system is provided to form an image on the imaging plane on the line sensor. In this relay lens system, the imaging magnification in the tangential direction is twice or more the imaging magnification in the sagittal direction. Also, the relay lens system includes

cylindrical lenses

044 and 045. Furthermore, at least one of the cylindrical lenses is preferably composed of a cemented lens so as to have an achromatic structure in order to suppress the chromatic aberration of the optical system. Further, if the relay lens system is an image-side telecentric optical system, each principal ray will be vertically incident on the cylindrical lens, and the lens power received by each light flux will be equal.

The measurement apparatus described above further includes a scanning unit that scans the line beam on the subject eye 026 in a direction perpendicular to the extending direction of the line beam. The above-described galvanometric mirror 023 is an example of this scanning unit, and various known scan mirrors can be used. The light source 001 is a wavelength sweeping type light source that sweeps the wavelength of light to be emitted. Furthermore, the light spot SP or the light spot SP 'is defined by a point spread function, more preferably, by a half width in the point spread function.

Further, in the present embodiment, an OCT apparatus is taken as an example of the measuring apparatus. In the OCT apparatus, in addition to the above-described configuration, the reference optical system 103 for adjusting the optical path length of the reference light from the light source 001, the reference light passing through the reference optical system 103 and the measurement light passing through the eye 026 are combined. And a combining unit that generates interference light by causing waves to wave. In the embodiment described above, the beam splitter 004 is exemplified as the combining unit, but is not limited to this as long as it has the same function. Further, the line sensor 046 receives this interference light and generates an output signal.

Further, in this embodiment, an OCT apparatus having a Mach-Zehnder interference system is taken as an example. That is, the OCT apparatus includes a division stage that divides the light from the light source 001 into measurement light and reference light before generating a line beam. In the embodiment, the coupler 002 is illustrated as a division unit, but the invention is not limited to this as long as the coupler 002 has the same function. The reference optical system 103 forms a second line beam from the reference light separately from the line beam formed from the measurement light. Then, the beam splitter 004 combines the line beam of the measurement light and the second line beam of the reference light to generate a line-like interference light.

As described above, according to the present embodiment, when an object point on the fundus is imaged on a line sensor in which square pixels are arranged in a line, an anisotropic magnification is used via a relay optical system. It is supposed to be imaged. As a result, the light spot from the object point is imaged within the pixel width in the width direction (sagittal direction) of the pixel so as to satisfy the light receiving efficiency. In addition, the light spot can be received by at least two or more pixels so as to satisfy the sampling theorem in the longitudinal direction (tangential direction) of the line sensor. Therefore, detection sensitivity and resolution can be maintained even when using a line sensor in which pixels of a cheaper configuration are arranged in a line. In addition, since the line sensor of one row of pixels is used, readout of a signal from the line sensor can be facilitated, and the time required for this can be shortened as compared with the line sensor disclosed in Non-Patent Document 1. That is, compared to the conventional configuration, it takes less time for signal readout.

Second Embodiment
In recent years, it is also required to obtain a tomogram of a wide range (full range) in both the width direction and the depth direction of the fundus in a short time using OCT. OCT which acquires such a wide-area tomogram is called full-range OCT. The application of line OCT to this full range OCT is being considered. Here, in OCT, there are various artifacts that can cause problems in data analysis or processing, one of which is 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, in the tomographic image, 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. If the mirror image overlaps the real image, it can lead to misanalysis of the data.

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 complex conjugate interference signal can be acquired by performing Fourier transform processing on the interference signal obtained in this state not in the normal A scan direction but in the spatial direction of the B scan and analyzing the signal. By taking the acquired complex conjugate interference signal as a zero value and performing normal Fourier transform processing on the remaining signal, a tomographic image from which the complex conjugate artifact has been removed can be obtained.

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. On the other hand, if the relay optical system is configured to receive the light spot SP 'with four pixels in the tangential direction, for example, the resolving power is doubled even if the sampling theorem is satisfied. Therefore, even if the complex conjugate artifact is removed, a full-range tomogram can be obtained while maintaining the original lateral resolution.

Hereinafter, a line OCT apparatus according to a second embodiment which enables such full range OCT to be performed will be described. In the description, the same reference numerals will be appended to the same or similar components as those described in the first embodiment, and the description thereof will be omitted. In the following, portions different from the first embodiment will be described.

(Reference optical system)
FIG. 6 is a view showing a schematic configuration of an OCT optical system in a line OCT apparatus according to a second embodiment. In the present embodiment, the configuration of the reference optical system 103 is different. The reference optical system 103 'of the present OCT optical system includes, in order from the emission end of the optical fiber, a collimator lens 031, an ND filter 032, a mirror 033, a mirror 034, a retroreflector 035, a mirror 019, a cylindrical lens 036, a lens 037, and a wavefront tilt. It has a mirror 038, a lens 039, and a lens 040. The reference optical system 103 ′ in the present embodiment differs from the reference optical system 103 in the first embodiment in having a wavefront tilt mirror 038 and a relay lens system for reference light consisting of a lens 039 and a lens 040. The cylindrical lens 036 and the lens 037 constitute a line beam forming lens system, and form a line beam of reference light as an intermediate image on the surface of the wavefront tilt mirror 038. The intermediate line image passes through the beam splitter 004 via a reference light relay lens system consisting of a lens 039 and a lens 040 to form a line beam of reference light on a virtual plane 041.

(Relay lens system for reference light)
7A and 7B illustrate in detail a part of the reference optical system 103 'in FIG. As described above, an intermediate line image is formed on the wavefront tilt mirror 038 by the cylindrical lens 036 and the lens 037. In the present embodiment, the wavefront tilt mirror 038 shown in FIG. 7A is disposed in the direction of 45 degrees 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 039 and the lens 040 will be described. Assuming that the focal length of the lens 039 is F39, the lens 039 is disposed at a distance from the wavefront tilt mirror 038 by F39. That is, the intermediate line image coincides with the front focal plane of the lens 039. At this time, a pupil image of an intermediate line image is formed on a virtual plane IP which is a back focal plane of the lens 039. 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 IP, while the light beam in the tangential direction indicated by the dashed line collected in the intermediate line image is the virtual plane IP It is collimated above. That is, while the line axis is rotated 90 degrees, a pupil image of the intermediate line image is formed on the virtual plane IP.

On the other hand, assuming that the focal length of the lens 040 is F40, the lens 040 is disposed at a distance of F40 from the virtual plane IP. That is, the virtual plane IP coincides with the front focal plane of the lens 040. At this time, a line beam relayed to the intermediate line image is formed on the back focal plane of the lens 040. If F39 and F40 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 040 coincides with the virtual plane 041 on which the line beam of the measurement light (return light) passing through the sample optical system 102 is formed, the virtual plane 041 is obtained. The reference light and the measurement light are combined in Therefore, as shown in, for example, a tomogram Ta1 shown in FIG. 8 described later, a tomogram without inclination is obtained from the interference signal having no phase shift obtained in this state.

Here, in the reference light, it is necessary to tilt the wavefront for the full range processing described later. FIG. 7B shows the case where the wavefront tilt mirror 38 is given a tilt different from 45 degrees. The change in inclination of the wavefront inclination mirror 038 can be electrically controlled using a stepping motor or the like (not shown) attached to the wavefront inclination mirror 038 by mirror driving means (not shown). When the wavefront inclination mirror 038 is inclined by 45 + θ / 2 degrees, the central angle of the reference light after reflection is inclined 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 that has passed through the lens 039 forms a pupil image on the virtual plane IP, but its formation position is shifted by F39 × tan θ. Thereafter, a lens 040 forms a line beam of reference light relayed on the virtual plane 041. However, since the pupil image on the virtual plane IP is shifted by F39 × tan θ, the collimated light beam directed to the virtual plane 041 is also inclined uniformly by θ ′. That is, the wavefront of the reference light on the virtual plane 041 is inclined by θ '. Here, when F23 = F24, θ ′ = − θ, and when F39 ≠ F40, the relationship of θ ′ = − θ × F39 / F40 is obtained. In addition, since the inclination of the wavefront inclination mirror 038 is given only in the tangential direction of the 1 axis direction, the imaging relationship of the light beam in the sagittal direction indicated by the solid line is unchanged.

Here, the intermediate line image on the wavefront tilt mirror 038 is in a conjugate relationship with the virtual plane 041 via the lens 039 and the lens 040. For this reason, the center of the reference light reflected at the center of the optical axis of the wavefront tilt mirror 038 arrives on the optical axis of the optical system again without being shifted on the imaginary plane 041 plane. With such a configuration, for example, it is possible to ideally provide only the change of the wavefront to the reference light without causing the vignetting or the decrease of the light intensity distribution due to the shift of the reference light. The configuration of the reference light relay lens system is not limited to the one suitably shown here, and various modifications can be made as long as the intermediate image formed on the wavefront tilt mirror 038 is relayed on the virtual plane 041. Is possible.

(Full range processing)
FIG. 8 shows an example of a tomogram of the fundus of the eye to be examined 026 obtained by the signal processing unit 053. 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 038, 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. 9 is an example of a processing process called full range processing performed by the signal processing unit 053. In the full range processing, the following processing disclosed in Non-Patent Document 1 is performed. First, with respect to the interference signal from the subject eye 026 acquired by the line sensor 046, Fourier transform processing is performed in the B scan direction, and frequency analysis of the structure 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 prior art, accurate tomographic information can be obtained only from a region apart from the normal image and the mirror image without overlapping, which limits the obtained depth information. On the other hand, even at the zero delay position, since a normal image separated from the mirror image is obtained, 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 deleted. However, in the present embodiment, so-called oversampling is performed in advance to obtain an interference signal by receiving the light spot SP with at least four or more pixels, so that the sampling theorem is satisfied and the resolution is theoretically reduced to half. Also, tomograms can be obtained with appropriate resolution.

The horizontal axis of the graph shown in FIG. 9 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, since it is difficult to display correct tomographic information in the region where the normal image and the mirror image overlap, 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 zero frequency, and furthermore, 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 038 is such that, in the light beam reaching the line sensor 046, the 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. 9 is suitably 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.

As described above, in the present embodiment, the reference optical system 103 includes means for giving a phase shift to the measurement light to the reference light. The means comprises a wavefront tilt mirror 038 and a relay lens system for reference light provided with a lens 039 and a lens 040. By appropriately tilting the wavefront tilt mirror 038 with respect to the optical axis and tilting the line-like reference beam to make it enter the virtual plane 041, the reference beam can be given a suitable phase shift. Further, in the line OCT apparatus performing the above-described full range processing by giving a phase shift to the reference light, the light spot SP ′ is imaged so as to include at least four pixels PXb adjacent in the lateral direction of the line sensor 046. This makes possible suitable resolution. The configuration for providing the phase shift to the reference light is not limited to the one suitably shown here, and various modifications can be made as long as it is possible to provide an appropriate phase shift to the reference light.

As described above, by forming the reference optical system 103 ′ and the like, in full-range OCT, a tomogram having sufficient resolution can be obtained even if the mirror image accompanying complex conjugate ambiguity is removed by the phase shift method. Can. Further, if the additional rotation of the wavefront tilt mirror 038 is not performed and the removal of the mirror image is not performed by the phase shift method, the tomographic image of the detailed resolution is not accompanied with the data reduction as in the normal line OCT apparatus. You can also get it.

[Modification 1]
In the embodiment described above, the relay optical system disposed in the light receiving optical system causes the point image from the fundus to have a diameter corresponding to the pixel width of the line sensor 046 in the sagittal direction, and light reception by a plurality of pixels in the tangential direction It is assumed that the light is collected so as to have the desired diameter. However, the imaging magnification in the sagittal direction is not limited to the magnification described here. For example, as shown in FIG. 10, in the light spot SP ′ obtained with an anisotropic magnification, the diameter in the width direction of the pixel may be smaller than the actual pixel width at the time of imaging. That is, the ratio of anisotropy may be increased while maintaining the resolution. In this case, the light spot SP ′ is imaged as shown on the line sensor 046 in which the pixels PXb are arranged. At this time, in the width direction of the pixel, the width of the pixel is sufficiently larger than the light spot SP ′. With such a configuration, for example, when a shift in the optical axis in the sagittal direction occurs in the optical system, there is a sufficient margin in the magnitude relationship between the line beam and the line sensor 046. The sensitivity to degradation can be reduced.

[Modification 2]
In the embodiment described above, the relay optical system is disposed in the light receiving optical system, and the imaging magnification in the sagittal direction of the light spot SP and the imaging magnification in the tangential direction are changed by the relay optical system. Then, as a result, the light spot SP ′ is made to be equal to or less than the pixel width in the width direction of the line sensor 046 and to be imaged so as to be received by a plurality of pixels in the length direction. There is. However, the configuration for focusing the light spot SP on the line sensor 046 is not limited to the above. Specifically, the condition described above may be satisfied by changing the shape of the line sensor 046 in the light receiving optical system.

More specifically, it is also possible to satisfy the condition by changing the aspect ratio of the individual pixels in the line sensor 046. In this case, the relay optical system in the light receiving optical system 104 is not necessary, and the interference light formed on the virtual plane 041 is directly received by the line sensor 046. In such a modification, the state in which the light spot SP is formed on the line sensor 046 is shown in FIGS. 11A and 11B. In the modified example shown in FIG. 11A, the light spot SP is imaged at the same magnification in the sagittal direction and the tangential direction. On the other hand, as the pixel PXa 'in the line sensor 046, a pixel whose length direction is 1/8 in the width direction is used. With this configuration, the light spot SP is contained within the width of the line sensor 046, and the light receiving efficiency is maintained, and the light spot SP is received by a plurality of (eight in the embodiment) pixels. It becomes. Thus, it is possible to realize a light receiving optical system that achieves both the light receiving efficiency of the line sensor and the spatial frequency.

Here, an example is shown in which the light spot SP is received by eight pixels aligned in the lateral direction. However, the number of pixels is not limited to this. Specifically, the number of pixels receiving the light spot may satisfy the sampling theorem. Therefore, in the light receiving optical system 104, the pixels constituting the line sensor 046 may be at least twice as long as the sagittal direction with respect to the tangential direction. In addition, in the case of applying this modification to the full-range OCT shown in the second embodiment, the length in the sagittal direction may be at least four times or more the length in the tangential direction.

FIG. 11B shows a case corresponding to the above-described first modification in which the ratio of anisotropy is further increased by 1.5 times while maintaining the resolution. In this case, the pixel PXc and the formed light spot SP have a relationship as shown in the figure. At this time, in the line width direction, the line width of the line sensor 046 is sufficiently larger than the light spot SP. With such a configuration, for example, when a shift in the optical axis in the sagittal direction occurs in the optical system, there is a sufficient margin in the magnitude relationship between the line beam and the line sensor 046. The sensitivity to degradation can be reduced. Thereby, a robust optical system can be realized.

As described above, according to the present invention, it is possible to realize an imaging optical system in which the light reception efficiency of the line sensor and the spatial frequency are compatible in signal reception of the line sensor in the line OCT. In addition, since the line sensor is composed of light receiving elements arranged in a line in the tangential direction, signal readout is easy. For example, compared with the case of the sensor disclosed in Non-Patent Document 1, the signal readout time is It can be shortened. Further, by making the width direction of the line sensor and the size of the light spot have an appropriate relationship, it is possible to maintain the received light quantity within a certain range even for the optical axis deviation, and it is possible to realize a robust optical system.

[Other embodiments]
In the above, the example which applied this invention to the line OCT apparatus is described. However, the device to which the present invention is applied is not limited to the line OCT device. The present invention is applicable to any device that shapes measurement light into a line shape, scans the fundus of the eye to be examined, and collectively acquires information from the fundus. That is, the present invention can also be applied to, for example, the line SLO for scanning a line-shaped measurement light to acquire a fundus image.

Further, in the embodiment described above, in particular, the fundus of the human eye (retina) is taken as an example of the test object. 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.

Although the present invention has been described above with reference to the examples, the present invention is not limited to the above-described examples. 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 the priority of Japanese Patent Application No. 2017-158042 filed on Aug. 18, 2017, the contents of which are incorporated herein by reference.

101 Line Image Forming Optical System 102 Sample Optical System (Measurement Optical System)
103 Reference optical system 104 Light receiving optical system 001 Light source 002 Coupler 026 Eye 46 to be examined Line sensor 053 Signal processing means SP Light spot PXa, PXb Pixel SI 'Intermediate image plane

Claims

Light source,
A measurement optical system which shapes the measurement light from the light source as a line beam and guides it to an inspection object;
A light receiving optical system that receives the measurement light having passed through the inspection object by a line sensor in which pixels are arranged in a tangential direction, and generates an output signal;
Signal processing means for processing the output signal and outputting measurement information of the inspection object;
Equipped with
In the light receiving optical system, a light spot obtained by imaging an object point on the inspection object on the line sensor is a light receiving area of at least two of the pixels adjacent to the tangential direction of the line sensor. And measuring the image so as to be in the sagittal direction of the light receiving area of the pixel.
The light receiving optical system forms an image formed on an intermediate image plane formed at a position conjugate to the object point on an optical path from the inspection object to the line sensor on an imaging surface on the line sensor. It has a relay lens system that
The measuring apparatus according to claim 1, wherein in the relay lens system, an imaging magnification in the tangential direction is twice or more of an imaging magnification in the sagittal direction.
The measurement device according to claim 2, wherein the relay lens system comprises a cylindrical lens.
The said cylindrical lens consists of a bonding lens, The measuring device of Claim 3 characterized by the above-mentioned.
The measuring apparatus according to any one of claims 2 to 4, wherein the relay lens system is an image-side telecentric optical system.
2. The measurement apparatus according to claim 1, wherein in the light receiving optical system, the length in the sagittal direction is twice or more the length in the tangential direction with respect to the length in the tangential direction.
The measurement according to any one of claims 1 to 6, further comprising scanning means for scanning the line image on the inspection object in a direction perpendicular to the extending direction of the line beam. apparatus.
The measurement apparatus according to any one of claims 1 to 7, wherein the light source is a wavelength sweeping type light source that sweeps the wavelength of light to be emitted.
A reference optical system for adjusting an optical path length of reference light from the light source;
It further comprises combining means for combining the reference light that has passed through the reference optical system and the measurement light that has passed through the object to generate interference light.
The measurement apparatus according to any one of claims 1 to 8, wherein the line sensor receives the interference light and generates the output signal.
It further comprises a dividing means for dividing the light from the light source into the measurement light and the reference light,
The reference optical system forms a second line beam of the reference light,
10. The measurement apparatus according to claim 9, wherein the combining means combines the line beam and the second line beam to generate a line-like interference light.
The reference optical system comprises means for applying a phase shift to the measurement light to the reference light,
The measuring apparatus according to claim 9, wherein the light spot is imaged so as to include at least four light receiving areas adjacent in the lateral direction of the line sensor.
The measuring apparatus according to any one of claims 1 to 11, wherein the light spot is defined by a point spread function.
The measurement apparatus according to claim 12, wherein the light spot is defined by a half width in the point spread function.