JP2019033956A - Measurement apparatus - Google Patents

Abstract

To provide a measurement apparatus which is structured less expensively, yet capable of maintaining detection sensitivity and which needs no signal read time.SOLUTION: The measurement apparatus comprises: a light source; a measurement optical system 102 which shapes measurement light from the light source into a line image and guides it to a subject; a light receiving optical system 104 which uses a line sensor with pixels arranged in a tangential direction to receive measurement light transmitted through the subject to generate an output signal; and signal processing means which processes the output signal and outputs measurement information of the subject. In the light receiving optical system, a light spot obtained by focusing an object point on the subject onto a line sensor includes light reception regions of at least two pixels arranged adjacent in the tangential direction of the line sensor, and is formed to enter the light reception regions in a sagittal direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a measuring apparatus that scans light on an inspection object and measures the inspection object.

  In the field of ophthalmology, an optical measurement device that scans measurement light on or inside an eye to be examined and inspects the eye to be examined is known. In particular, in recent years, an apparatus (hereinafter referred to as an OCT apparatus) using an optical coherence tomography (OCT) capable of observing / measuring a fundus and an anterior segment of the fundus in a non-invasive manner has been spreading. In OCT, low-coherent light (measurement light) is irradiated to the eye, and information on the tomogram of the eye is obtained using interference light obtained by combining the return light from the eye and the reference light. Yes. Further, by scanning the measurement light over a predetermined range on the eye fundus of the eye to be examined, three-dimensional tomographic information in the predetermined range can be obtained. An OCT apparatus that embodies this method is widely used in medicine from research to clinical practice.

  OCT is roughly classified into two types, time domain OCT and Fourier domain OCT. Further, the Fourier domain OCT includes a spectral domain OCT (SD-OCT) and a swept source OCT (SS-OCT). These Fourier domain OCTs use light from a light source having a wide wavelength band, perform signal acquisition by dispersing the obtained interference light, and perform processing such as Fourier transform on the acquired signal, thereby allowing the eye to be examined. I have information. SD-OCT using broadband light obtains information for each frequency by spatially separating the obtained interference light with a spectroscope. In SS-OCT using light from a wavelength-swept light source, information from each frequency is obtained by temporally dispersing the obtained interference light using light from a light source that emits light having different wavelengths in time. .

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

DJ Fechtig, B. Grajciar, T. Schmoll, C. Blatter, RM Werkmeister, W. Drexler, and R. a Leitgeb, “Line-field parallel swept source MHz OCT for structural and functional retinal imaging.,” Biomed. Opt. Express, vol. 6, no. 3, pp. 716-35, Mar. 2015. (https://www.osapublishing.org/boe/fulltext.cfm?uri=boe-6-3-716&id=311687)

  In general, an optical device such as a line sensor has a sampling theorem, and in order to preserve the maximum spatial frequency included in a signal, it is necessary to sample at an interval equal to or less than half the spatial frequency (Nyquist frequency). Therefore, for the optical resolution at which the point image from the fundus of the subject's eye as an object point is formed as a spot image on the line sensor, the pixel interval is good if it is not as fine as half or less of the diameter of the spot image. Spatial resolution cannot be obtained. For example, when a line sensor composed of square pixels having a side of 10 [μm] is used, the diameter of the spot image that can be handled is 20 [μm].

  Here, when selecting a line sensor which is an important device in the line OCT apparatus, it is necessary to consider the detection sensitivity. In order to increase the light receiving efficiency of the line sensor in order to optimize the detection sensitivity, generally, a cylindrical lens is disposed immediately before the line sensor so as to collect 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 image 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 less than the pixel width. Therefore, in the case of a line sensor in which square pixels of the size described above are arranged in a line, the spot image diameter is preferably 10 [μm] or less. When the spot image diameter is 20 [μm], the pixel width 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 Non-Patent Document 1 uses a sensor in which line arrays of pixels having the above-described sizes are arranged in two stages in the vertical direction. The spot image is received by a plurality of pixels arranged in the width direction and the vertical direction, thereby satisfying the sampling theorem and the maintenance of the light receiving efficiency. However, such a two-stage line sensor is expensive because of its complicated structure, and it may take a long time to read a signal.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a measurement apparatus that has a lower cost configuration, can maintain detection sensitivity, and does not require signal readout time.

In order to solve the above problems, a measurement device according to one embodiment of the present invention includes:
A light source;
A measuring optical system for shaping the measuring light from the light source as a line image and guiding it to the object to be inspected;
A light receiving optical system that receives the measurement light that has 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;
With
In the light receiving optical system, a light spot obtained by forming an image of an object point on the inspection object on the line sensor has a light receiving area of at least two pixels adjacent to the tangential direction of the line sensor. And forming an image so as to fall within a sagittal direction of the light receiving region of the pixel.

  According to the present invention, it is possible to provide a measurement device that has a lower cost configuration, can maintain detection sensitivity, and does not require signal readout time.

It is a schematic block diagram for demonstrating the optical system of the line OCT apparatus which concerns on 1st Example of this invention. It is a block diagram for demonstrating the control part of the line OCT apparatus which concerns on 1st Example of this invention. It is the schematic for demonstrating the relationship between the spot image diameter and sensor size at the time of making it image on the line sensor which consists of square pixels by making the point image in a fundus into a light spot. It is a schematic block diagram of the relay optical system in the light reception optical system shown in FIG. FIG. 5 is a schematic perspective view of the relay optical system shown in FIG. 4. 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. FIG. 7 is a schematic configuration diagram of a line image forming optical system, a wavefront tilt mirror, and a reference light relay lens system in the reference optical system shown in FIG. 6. It is a figure which illustrates the tomogram normally obtained and the 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.

  Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, dimensions, materials, shapes, and relative positions of components 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, the same reference numerals are used between the drawings to indicate the same or functionally similar elements.

[First embodiment]
In the following embodiments, a line OCT apparatus will be described as an example of a measuring apparatus to which the present invention is applied. FIG. 1 to be referred to is a schematic configuration diagram for explaining an optical system of the line OCT apparatus, and FIG. 2 is a block diagram showing an overall configuration of the line OCT apparatus for explaining a control unit of the line OCT apparatus. The line OCT apparatus shown in this embodiment has a Mach-Zehnder type interference system instead of a Michelson type interference system. However, a Michelson interference system may be used.

  The OCT optical system in the line OCT apparatus according to the present embodiment includes a light source 001, a coupler 002, a line image 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. 104. Light emitted from a wavelength-swept light source 001 (SS light source) is guided to a coupler (optical coupler) 002 by an optical fiber, and is split into measurement light and reference light by the coupler 002 under a desired division ratio. . The measurement light is guided to the line image forming optical system 101 and the reference light is guided to the reference optical system 103 via optical fibers. Note that 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 image forming optical system)
The line image forming optical system 101 includes a collimator lens 011, a cylindrical lens 012, and a lens 013 in order from the coupler 002 side. The measurement light obtained from the coupler 002 is guided to the line image forming optical system 101 and is made collimated light by the collimator lens 011. The collimated light is further shaped into a linear light beam that forms a line image on the virtual plane 014 by the cylindrical lens 012 and the lens 013. In the figure, a solid line indicates a light beam collected on the virtual plane 014 in a sagittal direction perpendicular to the paper surface, and a broken line indicates a light beam collimated on the virtual plane 014 in a tangential direction parallel to the paper surface. .

(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 a focus lens 021, a diaphragm 022, a galvanometric mirror 023, a lens 024, and a lens 025 in order from the beam splitter 004 side. The galvanometric mirror 023 is disposed at a position substantially conjugate with the anterior segment of the eye 026 to be examined, 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 the measurement light to the eye 026 to be examined to form a line image on the fundus.

  The focus lens 021 can be moved on the optical axis by a focus driving means 0081 described later. The position of the focus lens 021 on the optical axis is controlled so that the virtual plane 014 and the fundus of the eye 026 to be examined are optically conjugate. Further, the line image by the measurement light guided onto the fundus is scanned on the fundus in the state of the line image by the rotational drive of the galvanometric mirror 023. The measurement light reflected and scattered by the fundus of the eye 026 to be examined is transmitted back to the 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 a line image of measurement light (return light) on a virtual plane 041 described later.

(Reception optical system)
The light receiving optical system 104 includes 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, the virtual plane 041 located near the exit surface of the beam splitter 004 is optically conjugate with the fundus and virtual plane 014 of the eye 026 to be examined. Further, the virtual plane 041 is also conjugate with the light receiving surface of the line sensor 046 through the lens 042, the lens 043, the cylindrical lens 044, and the cylindrical lens 045 in the relay optical system. For this reason, the measurement light (returned light) reflected and scattered from the line image on the fundus reaches the line sensor 046 and forms an image.

(Reference optical system)
On the other hand, the reference light divided by the coupler 002 is guided to the reference optical system 103 through an optical fiber. The reference optical system 103 includes 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 order from the emission end of the optical fiber. The reference light converted into collimated light 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 maintaining the collimated state, is folded back by the retro reflector 035 movable in the optical axis direction, and is reflected by the mirror 034 and the mirror 033 again. Further, the reference light is shaped by the cylindrical lens 036 and the lens 037, passes through the beam splitter 004, and then forms a line image by the reference light on the virtual plane 041. The cylindrical lens 036 and the lens 037 constitute a line image forming lens system. The retro-reflector 035 can be moved on the optical axis by reflector driving means 0071 described later, and can adjust 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. it can.

(Interference optics)
In this embodiment, the interference optical system is constituted by a 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 eye 026 via the sample optical system 102 are combined by the beam splitter 004, and line images of the reference light and the measurement light are displayed on the virtual plane 041. have a finger in the pie. The interfering line image 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, a polarization adjustment paddle 003 in which a plurality of optical fibers are bundled in an annular shape is disposed on the optical fiber from the coupler 002 to the reference optical system 103. The polarization adjustment paddle 003 is also provided with polarization adjustment drive means 0061 for driving it. 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 that the interference state between the measurement light and the reference light is improved.

(Control system)
As shown in FIG. 2, the line OCT apparatus according to 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. 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, control signals and the like are input to these components, and output signals from these components are received.

  The operation input unit 056 is an input device for giving an instruction to the control unit 054, and includes, for example, a keyboard and a mouse. 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, controls the line sensor 046, and acquires 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 such as 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 tomographic image. In addition, although the control means 054, the monitor 055, etc. which were described here in the figure are each shown individually, these may be comprised in part or whole as integral. Further, the control unit 054 and the OCT optical system may be configured as an integral unit.

  In addition to the configuration described above, the control unit 054 is also connected to the light source 001, the line sensor 046, the polarization adjustment driving unit 0061, the reflector driving unit 0071, the focus driving unit 0081, and the galvano driving unit 0091. These components are for controlling each component of the OCT optical system, and the control means 054 can control each component in the OCT optical system. The focus driving unit 0081 moves the focus lens 021 in the optical axis direction and controls the position of the focus lens 021 on the optical axis. The galvano driving means 0091 drives the galvanometric mirror 023 to scan the fundus of the line-shaped measurement light. The reflector driving means 0071 moves the retro reflector 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 the interference signal acquisition timing for 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 driving angle of the galvanometric mirror 023 is controlled by the galvano driving means 0091. The sampling unit 051 acquires 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 driving angle, and each pixel obtains one interference signal. And also in the next galvano drive angle, corresponding to the next wavelength sweep of the light source 001, this output signal is acquired for each pixel of the line sensor 046 to obtain the next interference signal. Thereafter, interference signals are acquired one after another by repeating this process. The interference signal acquired by the sampling unit 051 is stored in the memory 052 together with the galvano driving angle. The galvano driving angle is associated with the scanning position of the measurement light on the fundus. The interference signal stored in the memory 052 is subjected to frequency analysis by the signal processing unit 053 and associated with a position on the fundus. The tomographic image of the fundus of the subject eye 026 generated by the above processing is stored in the memory 052 and displayed on the monitor 055. As described above, by acquiring information on the galvano drive angle together with the interference signal, a three-dimensional fundus volume image can be generated and displayed on the monitor 055.

(Light receiving efficiency and resolving power)
Next, the imaging magnification when the fundus is imaged by the line sensor 046 will be described. In fundus imaging with the line OCT apparatus, interference light is received in a lump 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 oculi is spread by a point spread function (PSF) and becomes a light spot (point image) of a finite size and is formed as an image on the line sensor. . Hereinafter, regarding the light spot (point image) from the point object on the fundus oculi in the line image of the eye to be examined obtained by the line OCT apparatus, the relationship between the light spot and the pixels constituting the line sensor will be described.

  FIG. 3 is a diagram for explaining the relationship between the light spot imaged on the line sensor 046 and the size of the pixels constituting the line sensor 046. Usually, in the OCT apparatus, the line sensor 046 is composed of square pixels having isotropic widths in the sagittal direction and the tangential direction of the relay optical system. 3A shows the relationship between the light spot and the pixel when the light receiving efficiency of the line sensor 046 is prioritized, and FIG. 3B shows the light spot and the pixel when the spatial frequency of the line sensor 046 is prioritized. Shows the relationship. FIG. 3C shows the relationship between the light spot and the pixel when the present invention is applied. In the drawing, the light spot SP is indicated by a concentric circle, and the outermost circle of the concentric circle indicates a spot defined by the half-value width in the PSF. Here, the outermost circumference of the light spot where the point image spreads is defined using the half width, but it may be defined by 1/10 width. Further, an object point image may be used as it is as a light spot. Here, although described as a pixel, the pixel shown in FIG. 3 and the like is equivalent to a light receiving region in the light receiving element.

  FIG. 3A shows a case where the imaging magnification is set so that the light spot SP and the width of the pixel PXa in the line sensor 046 match. 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 cannot be appropriately resolved. On the other hand, FIG. 3B shows a case where the imaging magnification is set so that the width of the pixel PXb in the line sensor 046 is halved with respect to 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 because the information obtained from the light spot SP is received by at least two pixels. It can be properly resolved. 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 magnification in the sagittal direction and the tangential direction of a general relay optical system is isotropic, it is impossible to achieve both light receiving efficiency and resolving power.

  On the other hand, in the present invention, in the relay optical system when the line image formed on the virtual plane 041 is formed on the line sensor 046, the light spot SP is connected at different magnifications in the sagittal direction and the tangential direction. I am going to image. In the example shown in FIG. 3C, an image is formed so that the width of the pixel PXb and the diameter of the light spot coincide in the sagittal direction, and the diameter of the light spot matches the width of the eight pixels PXb in the tangential direction. Thus, an image is formed as an elliptical light spot SP ′. If such a relationship between the light spot SP ′ and the pixel can be established, it is possible to achieve a sufficient resolution of the light spot SP ′ by eliminating the loss of light receiving efficiency and receiving the light spot with 8 pixels. In this example, the light spot is received by 8 pixels. However, in order to satisfy the sampling theorem and light reception efficiency, the light spot is resolved by at least two pixels adjacent in the tangential direction and is sagittal. The image may be formed within the pixel width.

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

  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 forms a relay image of the line image on the virtual plane 041 on the image plane on the line sensor 046. In this 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 light spot can be imaged under the above-described conditions.

  In the present embodiment, in order to obtain sufficient resolving power while maintaining the light receiving efficiency, the relay image is formed so that the imaging magnification in the tangential direction is 8 times larger than the imaging magnification in the sagittal direction. Set. That is, if the line image is formed on the virtual plane 041 at the same magnification as the fundus, the relay optical system increases the line sensor width and the light spot diameter by 0.5 times in the sagittal direction. The image is reduced and imaged. In the tangential direction, the image is magnified 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 that 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 the object plane, and the line sensor 046 is the image plane. Therefore, when trying to obtain the imaging magnification, the object distance S43 that is the distance from the virtual plane 041 to the lens 043 and the image distance S43 ′ that is the distance from the lens 043 to the line sensor 046 (light receiving surface) are 1: 4 relationship. The lens 042 is a field lens arranged as an image-side telecentric optical system so that the principal ray in the light flux at each angle of view enters the cylindrical lens perpendicularly, and does not affect the imaging magnification. When each principal ray is perpendicularly incident on the cylindrical lens, the lens power received by the light flux at each angle of view becomes equal. Further, since the cylindrical lens 044 and the cylindrical lens 045 have no power, they do not affect the image formation. Here, if 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]. Thus, the focal length F43 of the lens 043 is 24 [mm]. By arranging in this way, the imaging magnification βt in the tangential direction is S43 '/ S43 = -4 as described above.

  On the other hand, FIG. 4B shows a cross section of an optical system that forms an image at 0.5 times in the sagittal direction. In this optical system, the power is provided by the lens 043, the cylindrical lens 044, and the cylindrical lens 045. The virtual plane 041 is the object plane, 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 image formation, the first object on the virtual plane 041 is formed as an image on the line sensor 046 by the lens 043 as in the tangential direction. Since this first image is affected by the subsequent power, there is no actual situation. The imaging magnification β1 by this first imaging is −4.

  Next, as the second image formation, when the first image is regarded as the second object, the second object is formed as a second image on the intermediate image plane SI ′ by the cylindrical lens 044. . This second image is not real. 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]. 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 length F44 of the cylindrical lens 044 is −20 [mm]. It becomes. The imaging magnification β2 by the second imaging is S44 '/ S44 = -0.5.

  Next, as a third image formation, when the second image is regarded as a third object, the third object is formed on the light receiving surface of the line sensor 046 by the cylindrical lens 045. To form an image. 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 =. -72 [mm]. 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 length F45 of the cylindrical lens 045 is 14.4 [mm]. . The imaging magnification β3 by the third imaging is S45 ′ / S45 = −0.25. By arranging each optical element in this way, the first imaging magnification, the second imaging magnification, and the third imaging magnification are multiplied as the imaging magnification βs in the sagittal direction. A magnification β1 × β2 × β3 = −0.5 is obtained.

  By configuring the relay optical system as described above, it is possible to realize an optical system with anisotropic magnification that forms images simultaneously in the tangential direction and the sagittal direction and has different magnifications. FIG. 5 shows a perspective view of the relay optical system in the present embodiment described above for reference. In the figure, the light flux of the line image is extracted for the center and the left and right three.

  Here, in this embodiment, it is assumed that the optical resolution on the fundus is 20 [μm], and that it is 20 [μm] even on the virtual plane 041 imaged at the same magnification. By using the relay optical system described above, the light spot forms an image with 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 is formed with a diameter of 20 × 4 = 80 [μm] in the tangential direction and light can be received by eight pixels with respect to one light spot, a sufficient resolving power can be obtained.

(Achromatic cylindrical lens)
Here, in general, in Fourier domain OCT, since a light source having a wide wavelength band is used, it is necessary to suppress chromatic aberration in all optical systems. In particular, the chromatic aberration in the sagittal imaging of the relay optical system causes nonuniformity in the light reception efficiency for each wavelength and affects the spectral spectrum shape of the interference signal, so the longitudinal resolution of the tomographic image obtained by signal processing is reduced. Deteriorating factor. Accordingly, 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 together. Thereby, chromatic aberration that may be caused by the relay optical system can be suppressed.

  As described above, the measuring apparatus according to the present embodiment includes at least 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 image and guides it to the eye 026 to be examined. The light receiving optical system 104 receives the measurement light passed through the eye 026 by the 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 026 to be examined. In the light receiving optical system 104, the light spot SP ′ obtained by forming an image of an object point on the eye to be examined (on the object to be inspected) on the line sensor 046 is at least 2 adjacent to the line sensor 046 in the tangential direction. It includes a light receiving area of two pixels PXb. In the light receiving optical system 104, the light spot SP 'is imaged so as to enter the sagittal direction of the light receiving area of the pixel XPb.

  Here, as described above, the light receiving optical system 104 is imaged on the intermediate image plane (image of the virtual plane 041) formed at a position conjugate with the object point on the optical path from the subject eye 026 to the line sensor 046. A relay lens system that forms an image on the imaging surface of the line sensor. In this relay lens system, the imaging magnification in the tangential direction is at least twice the imaging magnification in the sagittal direction. The relay lens system includes cylindrical lenses 044 and 045. Furthermore, at least one of the cylindrical lenses is preferably composed of a bonded lens so as to have an achromatic structure in order to suppress chromatic aberration of the optical system. Further, if the relay lens system is an image side telecentric optical system, each chief ray is perpendicularly incident on the cylindrical lens, and the lens power received by each light beam becomes equal.

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

  In this embodiment, an OCT apparatus is taken as an example of the measuring apparatus. In the OCT apparatus, in addition to the configuration described above, the reference optical system 103 that adjusts the optical path length of the reference light from the light source 001, the reference light that has passed through the reference optical system 103, and the measurement light that has passed through the eye 026 to be examined are combined. And a multiplexing means for generating interference light by generating waves. In the above-described embodiment, the beam splitter 004 is exemplified as the multiplexing unit. However, the beam splitter 004 is not limited to this as long as it has a similar function. The line sensor 046 receives this interference light and generates an output signal.

  In this embodiment, an OCT apparatus having a Mach-Zehnder type interference system is taken as an example. That is, the OCT apparatus includes a dividing unit that divides the light from the light source 001 into measurement light and reference light before generating a line image. In the embodiment, the coupler 002 is exemplified as the dividing unit. However, the coupler 002 is not limited to this as long as it has the same function. The reference optical system 103 forms a second line image from the reference light separately from the line image formed from the measurement light. The beam splitter 004 generates a line-shaped interference light by combining the line image based on the measurement light and the second line image based on the reference 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 obtained via a relay optical system. It is supposed to form an image. Thereby, a light spot from the object point is imaged within the pixel width in the pixel width direction (sagittal direction) so as to satisfy the light receiving efficiency. Further, with respect to the length direction (tangential direction) of the line sensor, the light spot can be received by at least two or more pixels so as to satisfy the sampling theorem. Therefore, even if a line sensor in which pixels having a cheaper configuration are arranged in a row is used, detection sensitivity and resolution can be maintained. In addition, since the line sensor of one pixel row is used, it is easy to read out signals from the line sensor, and the time required for this can be shortened compared to the line sensor disclosed in Non-Patent Document 1. That is, the signal reading time is not required as compared with the conventional configuration.

[Second Embodiment]
In recent years, it has also been required to obtain tomographic images in a wide range (full range) at once in a short time in the width direction and depth direction of the fundus using OCT. Such OCT for acquiring a wide range of tomographic images is referred to as full-range OCT. The application of the line OCT to this full range OCT is being studied. Here, in OCT, there are various artifacts that can cause problems in data analysis or processing, and one of them is a complex conjugate artifact. Since the interference signal is detected as a real value, a complex conjugate ambiguity is generated in the depth profile reconstructed by the Fourier transform process. Specifically, in the tomographic image, a complex conjugate artifact appears as a mirror image of the real image on the side opposite to 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 may lead to erroneous data analysis.

  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. In other words, a phase shift is generated by giving a constant inclination to the wavefront of the reference light formed in a line and giving time delays at equal intervals in the B scan direction (reference light extending direction). The complex conjugate interference signal can be acquired by performing Fourier transform processing on the interference signal obtained in this state in the spatial direction of the B scan instead of the normal A scan direction and analyzing the signal. The acquired complex conjugate interference signal is set to a zero value, and a normal Fourier transform process is performed on the remaining signal, thereby obtaining a tomographic image from which the complex conjugate artifact is removed.

  However, by setting the complex conjugate interference signal to zero as described above, the data actually used for image formation is reduced to ½, and the lateral resolution is deteriorated. On the other hand, for example, if the relay optical system is configured so that the light spot SP 'is received by four pixels in the tangential direction, the resolving power is doubled as usual even if the sampling theorem is satisfied. Therefore, even if the complex conjugate artifact is removed, a full-range tomographic image can be obtained while maintaining the original lateral resolution.

  The line OCT apparatus according to the second embodiment that makes it possible to perform such full-range OCT will be described below. In the description, the same reference numerals are given to the same or similar components as those described in the first embodiment, and the description thereof is omitted here. Hereinafter, parts different from the first embodiment will be described.

(Reference optical system)
FIG. 6 is a diagram illustrating a schematic configuration of an OCT optical system in the line OCT apparatus according to the second embodiment. In this embodiment, the configuration of the reference optical system 103 is different. The reference optical system 103 ′ of the present OCT optical system includes 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, a wavefront tilt in order from the emission end of the optical fiber. A mirror 038, a lens 039, and a lens 040 are included. The reference optical system 103 ′ in this embodiment is different from the reference optical system 103 in the first embodiment in that it includes a wavefront tilt mirror 038 and a reference light relay lens system including a lens 039 and a lens 040. The cylindrical lens 036 and the lens 037 constitute a line image forming lens system, and form a line image of reference light as an intermediate image on the surface of the wavefront tilt mirror 038. The intermediate line image is further transmitted through a beam splitter 004 through a reference light relay lens system including a lens 039 and a lens 040 to form a line image based on the reference light on the virtual plane 041.

(Relay lens system for reference light)
FIG. 7 shows a part of the reference optical system 103 ′ in FIG. 6 in detail. 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 this embodiment, the wavefront tilting mirror 038 shown in FIG. 7A is arranged in a direction of 45 degrees with respect to the optical axis, so that the central axis of the reflected reference light is the optical axis of the subsequent optical system. Matches.

  Here, the positional relationship between the lens 039 and the lens 040 will be described. When the focal length of the lens 039 is F39, the lens 039 is arranged at a distance away 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 the virtual plane IP which is the rear focal plane of the lens 039. That is, the light beam in the sagittal direction indicated by the solid line that has been collimated in the intermediate line image is condensed on the virtual plane IP, while the light beam in the tangential direction indicated by the broken line that is condensed in the intermediate line image is the virtual plane IP. It will be collimated above. That is, a pupil image of an intermediate line image is formed on the virtual plane IP with the line axis rotated by 90 degrees.

  On the other hand, when the focal length of the lens 040 is F40, the lens 040 is disposed at a distance away from the virtual plane IP by F40. In other words, the virtual plane IP coincides with the front focal plane of the lens 040. At this time, a line image in which the intermediate line image is relayed is formed on the rear focal plane of the lens 040. If F39 and F40 are equal, these line images have the same magnification, and if they are different, the line image is multiplied by the magnification corresponding to the ratio. If the entire reference optical system is arranged so that the rear focal plane of the lens 040 coincides with the virtual plane 041 on which the line image of the measurement light (return light) that has passed through the sample optical system 102 is formed, the virtual plane 041 In this case, the reference light and the measurement light are combined. Therefore, from an interference signal without a phase shift obtained in this state, a tomographic image having no inclination is obtained, for example, as shown in a tomographic image Ta1 shown in FIG.

  Here, in the reference light, it is necessary to incline the wavefront for the full range processing described later. FIG. 7B shows a case where a tilt different from 45 degrees is given to the wavefront tilt mirror 38. The tilt change of the wavefront tilt mirror 038 can be electrically controlled by a mirror driving unit (not shown) using a stepping motor (not shown) attached to the wavefront tilt mirror 038. When the wavefront tilt mirror 038 is tilted by 45 + θ / 2 degrees, the center angle of the reflected reference light is tilted by θ. At this time, the rays in the collimating direction are uniformly inclined by θ, and at the same time, the wavefront which is the 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 line image of the reference light relayed on the virtual plane 041 by the lens 040 is formed. However, since the pupil image on the virtual plane IP is shifted by F39 × tan θ, the collimated light beam toward the virtual plane 041 is uniformly inclined by θ ′ accordingly. 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, θ ′ = − θ × F39 / F40. Note that since the inclination of the wavefront tilt mirror 038 is given only in the tangential direction of the uniaxial 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 038 has a conjugate relationship with the virtual plane 041 through the lens 039 and the lens 040. For this reason, the center of the reference light reflected at the optical axis center of the wavefront tilt mirror 038 reaches the optical axis of the optical system again without shifting on the virtual plane 041 surface. By adopting such a configuration, for example, vignetting and a decrease in light intensity distribution due to the shift of the reference light are not caused, and only a change in the wavefront can be ideally applied to the reference light. Note that the configuration of the reference light relay lens system is not limited to that suitably shown here, and various changes 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 tomographic image of the fundus of the eye to be examined 026 obtained by the signal processing unit 053. Ta1 is a tomographic image acquired when no inclination (angle θ) is given to the wavefront of the reference light. On the other hand, when the wavefront of the reference light is tilted (angle θ) by the wavefront tilt mirror 038, a tomographic image that is tilted as a whole like Tb1 is obtained. The uniform inclination of the wavefront is generally called a phase shift and causes a phase delay uniformly in the B-scan direction. Therefore, the tomographic image Tb1 has a linear depth in addition to the shape of the tomographic image Ta1. The position changes.

  FIG. 9 shows an example of a processing process called full range processing executed by the signal processing means 053. In the full range processing, the following processing disclosed in Non-Patent Document 1 is performed. First, the interference signal from the eye 026 to be examined acquired by the line sensor 046 is subjected to Fourier transform processing in the B-scan direction, and the frequency analysis of the structure is performed. As a result, a separable normal image (real image) and mirror image of the frequency signal are obtained. After removing the mirror image of the frequency signal, the complex signal of the original interference signal can be obtained by performing an inverse Fourier transform process on the normal image. A tomographic image from which a mirror image is removed can be acquired by subjecting this complex signal to Fourier transform in the A-scan direction in the same manner as normal OCT signal processing.

  Conventionally, accurate tomographic information can be obtained only from a region where the normal image and the mirror image do not overlap with each other, and thus the depth information obtained is limited. On the other hand, since a normal image separated from the mirror image can be obtained even at the zero delay position, it is possible to obtain tomographic information to a deeper depth. By performing the processing described here, the data corresponding to the mirror image is deleted, so the horizontal resolution is halved. However, in this embodiment, since so-called oversampling is performed in which the light spot SP is received in advance using at least four pixels to obtain an interference signal, the sampling theorem is satisfied and the resolution is theoretically halved. However, a tomographic image can be obtained with an appropriate resolution.

  The horizontal axis of the graph shown in FIG. 9 is frequency, and the vertical axis is intensity. A 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 a normal image and a mirror image generated symmetrically overlap each other. In this state, it is not easy to separate and remove the mirror image. In addition, since it is difficult to display correct tomographic information in a region where the normal image and the mirror image overlap, this region can be avoided and only the remaining tomographic information at a relatively shallow depth can be used.

  On the other hand, the frequency distribution Sb1 indicated by a broken line is a frequency distribution when the 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, both distributions are located away from the zero frequency, and the normal image and the mirror image are separated from each other. Specifically, assuming that the center wavelength of the light source 001 is λc, the wavefront tilt mirror 038 so that a light beam reaching the line sensor 046 uniformly gives a phase difference of λc / 4 between adjacent pixels of the line sensor. When the tilt angle is set, the frequency distribution can be satisfactorily separated. In such a state, the frequency distribution shown in FIG. 9 is preferably obtained, and the frequency signal of the mirror image can be easily set to a zero value, and the mirror image can be removed. Therefore, it is possible to acquire tomographic information from a wide range of wavelengths in the wavelength-swept light, and tomographic information from a deeper depth can be obtained.

  As described above, in this embodiment, the reference optical system 103 includes means for giving the reference light a phase shift with respect to the measurement light. The means includes a wavefront tilt mirror 038 and a reference light relay lens system including 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-shaped reference light so as to enter the virtual plane 041, a suitable phase shift can be given to the reference light. Further, in the line OCT apparatus that performs 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. A suitable resolution is possible. In addition, the structure which gives a phase shift to reference light is not limited to what is shown suitably here, A various change is possible if an appropriate phase shift can be provided to reference light.

  By configuring the reference optical system 103 ′ and the like as described above, it is possible to obtain a tomographic image having sufficient resolution even in the full-range OCT even if the mirror image due to the complex conjugate ambiguity is removed by the phase shift method. Can do. If the wavefront tilt mirror 038 is not additionally rotated by θ and the mirror image is not removed by the phase shift method, a tomographic image having a detailed resolution can be obtained without reducing data, as in the case of a normal line OCT apparatus. It can also be obtained.

[Modification 1]
In the embodiment described above, the point image from the fundus has a diameter corresponding to the pixel width of the line sensor 046 in the sagittal direction by the relay optical system arranged in the light receiving optical system, and is received by a plurality of pixels in the tangential direction. It is supposed that it will be condensed so that it may become the diameter which is done. 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 at an anisotropic magnification, the diameter in the width direction of the pixel may be made smaller than the actual pixel width at the time of image formation. That is, the anisotropy ratio may be increased while maintaining the resolution. In this case, the light spot SP ′ is imaged as shown in the figure 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 this configuration, for example, when an optical axis shift in the sagittal direction occurs in the optical system, there is a sufficient margin in the magnitude relationship between the line image and the line sensor 046, so that the line image is difficult to be captured, and the light receiving efficiency Sensitivity to decrease can be reduced.

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

  More specifically, the condition can be satisfied by changing the aspect ratio of each pixel 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 received by the line sensor 046 as it is. FIG. 11 shows a state where the light spot SP is imaged on the line sensor 046 in such a modification. In the modification 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, the pixel whose length direction is 1/8 with respect to the width direction is used. With this configuration, the light spot SP is accommodated within the width of the line sensor 046, so that the light receiving efficiency is maintained, and the light spot SP is received by a plurality of (eight in the embodiment) pixels. It becomes. As a result, 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.

  In this example, the light spot SP is received by eight pixels arranged in the horizontal direction. However, the number of pixels is not limited to this. Specifically, the number of pixels that receive the light spot may satisfy the sampling theorem. Accordingly, in the light receiving optical system 104, the pixels constituting the line sensor 046 only have to have a length in the sagittal direction at least twice as long as the length in the tangential direction. In addition, when the present modification is applied to the full range OCT shown in the second embodiment, the length in the sagittal direction may be at least four times the length in the tangential direction.

  FIG. 11B shows a case corresponding to the above-described modified example 1 in which the anisotropy ratio is further increased by 1.5 times while maintaining the resolution. In this case, the relationship between the pixel PXc and the focused light spot SP is as shown in the figure. At this time, the line width of the line sensor 046 is sufficiently larger than the light spot SP in the line width direction. With this configuration, for example, when an optical axis shift in the sagittal direction occurs in the optical system, there is a sufficient margin in the magnitude relationship between the line image and the line sensor 046, so that the line image is difficult to be captured, and the light receiving efficiency Sensitivity to decrease 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 that achieves both the light reception efficiency of the line sensor and the spatial frequency in the signal reception of the line sensor in the line OCT. Further, since the line sensor is composed of light receiving elements arranged in a line in the tangential direction, it is easy to read out the signal. For example, compared with the sensor disclosed in Non-Patent Document 1, the signal reading time is reduced. It can be shortened. In addition, when the width direction of the line sensor and the size of the light spot are in an appropriate relationship, the amount of received light can be maintained within a certain range even with respect to the optical axis shift, and a robust optical system can be realized.

[Other Examples]
In the above, the example which applied this invention to the line OCT apparatus was described. However, the apparatus to which the present invention is applied is not limited to the line OCT apparatus. The present invention is applicable to any apparatus that can form measurement light in a line shape, scan the fundus of the eye to be examined, and collectively acquire information from the fundus. In other words, the present invention can also be applied to, for example, a line SLO that acquires a fundus image by scanning a line-shaped illumination light.

  Further, in the above-described embodiment, the human eye, particularly the fundus (retina), is taken as an example of the inspection object. However, the object to be inspected is not limited to the fundus oculi, and may be an anterior ocular segment, a vitreous body, or the like. Moreover, it is not limited to eyes, Skin, an organ, etc. may be sufficient. In this case, the above-described line OCT apparatus 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 embodiments, the present invention is not limited to the above-described embodiments. Inventions modified within the scope not 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 mentioned above can be combined suitably in the range which is not contrary to the meaning of this invention.

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 to be examined 046 Line sensor 053 Signal processing means SP Light spot PXa, PXb Pixel SI ′ Intermediate image plane

Claims (13)

A light source;
A measuring optical system for shaping the measuring light from the light source as a line image and guiding it to the object to be inspected;
A light receiving optical system that receives the measurement light that has 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;
With
In the light receiving optical system, a light spot obtained by forming an image of an object point on the inspection object on the line sensor has a light receiving area of at least two pixels adjacent to the tangential direction of the line sensor. And measuring an image so as to enter a sagittal direction of the light receiving region of the pixel. The light receiving optical system connects an image formed on an intermediate image plane formed at a position conjugate with the object point on the optical path from the object to be inspected to the line sensor to the imaging plane on the line sensor. Equipped with a relay lens system
2. The measuring apparatus according to claim 1, wherein the relay lens system has an imaging magnification in the tangential direction that is at least twice the imaging magnification in the sagittal direction.   The measuring apparatus according to claim 2, wherein the relay lens system includes a cylindrical lens.   The measuring apparatus according to claim 3, wherein the cylindrical lens is a bonded lens.   The measuring apparatus according to claim 2, wherein the relay lens system is an image side telecentric optical system.   2. The measuring apparatus according to claim 1, wherein in the light receiving optical system, the length of the light receiving region in the sagittal direction is at least twice as long as the length in the tangential direction.   The measurement according to claim 1, further comprising scanning means for scanning the line image on the inspection object in a direction perpendicular to an extending direction of the line image. apparatus.   The measuring apparatus according to claim 1, wherein the light source is a wavelength sweeping type light source that sweeps a wavelength of emitted light. A reference optical system for adjusting the optical path length of the reference light from the light source;
A combining unit that generates interference light by combining the reference light that has passed through the reference optical system and the measurement light that has passed through the inspection object;
The measuring apparatus according to claim 1, wherein the line sensor receives the interference light and generates the output signal. Further comprising splitting means for splitting the light from the light source into the measurement light and the reference light;
The reference optical system forms a second line image of the reference light;
The measuring apparatus according to claim 9, wherein the combining unit generates the interference light in a line shape by combining the line image and the second line image. The reference optical system includes means for giving the reference light a phase shift with respect to the measurement light,
11. The measuring apparatus according to claim 9, wherein the light spot forms an image so as to include at least four light receiving regions adjacent in a lateral direction of the line sensor.   The measuring apparatus according to claim 1, wherein the light spot is defined by a point spread function.   The measuring apparatus according to claim 12, wherein the light spot is defined by a half-value width in the point spread function.

Images