Scanning optical system, scanning microscope, and scanning optical device

Abstract

This scanning optical system (SL) scans an illuminated surface with light via a scanning mechanism that changes the emission direction of light from a light source. The scanning optical system (SL) has a first lens group (G1) with positive or negative refractive power, a second lens group (G2) with positive refractive power, and a third lens group (G3) with negative refractive power, these being arranged in the above order from the scanning mechanism side, and the third lens group (G3) has a lens (L32) with a concave surface facing the illuminated surface.

Description

Scanning optical system, scanning microscope, and scanning optical device

[0001] The present invention relates to a scanning optical system, a scanning microscope, and a scanning optical device.

[0002] Conventionally, scanning microscopes equipped with a scanning optical system that guides light from a scanning mechanism to an objective optical system have been known (see, for example, Patent Document 1). In such scanning microscopes, it has been difficult to correct field curvature.

[0003] U.S. Patent No. 6,028,306

[0004] The scanning optical system according to the present invention is a scanning optical system that scans an illuminated surface with light transmitted through a scanning mechanism that changes the direction of light emitted from a light source, and has, arranged in order from the scanning mechanism side, a first lens group having positive or negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, wherein the third lens group has a lens with a concave surface facing the illuminated surface side, and satisfies the following conditional expression: 0.007<Σ(nd×tc / νd) / LA<0.021 1.05<(nd3j-1)×f / (nd3j×r3j)<1.5 Where, Σ(nd×tc / νd): the sum of nd×tc / νd of the lenses in the scanning optical system, where nd is the refractive index of the lenses constituting the scanning optical system with respect to the d-line, tc is the central thickness of the lenses, and νd is the Abbe number of the lenses with respect to the d-line. LA: the distance on the optical axis from the lens surface on the scanning mechanism side of the lens closest to the scanning mechanism among the lenses constituting the scanning optical system, to the lens surface on the irradiation surface side of the lens closest to the irradiation surface. nd3j: the refractive index of the lens with a concave surface facing the irradiation surface side. r3j: the radius of curvature of the lens surface on the irradiation surface side of the lens with a concave surface facing the irradiation surface side. f: the focal length of the scanning optical system with respect to the t-line.

[0005] The scanning microscope according to the present invention comprises a scanning mechanism that changes the emission direction of light from a light source, an objective optical system that focuses the light from the scanning mechanism on an irradiated surface on which a sample is placed, and the above-mentioned scanning optical system that is arranged between the scanning mechanism and the objective optical system and directs the light from the scanning mechanism to the objective optical system, and the scanning optical system scans the irradiated surface by changing the focusing position of the light focused on the irradiated surface in accordance with the emission direction of the light changed by the scanning mechanism.

[0006] The scanning optical device of the present invention comprises a scanning mechanism that changes the emission direction of light from a light source and the above-mentioned scanning optical system, and the scanning optical system scans the irradiated surface by changing the focusing position of the light focused on the irradiated surface in accordance with the emission direction of the light changed by the scanning mechanism.

[0007] 10 is a cross-sectional view showing the configuration of a scanning optical system according to a first embodiment. FIG. 11 is a diagram showing various aberrations of the scanning optical system according to the first embodiment. FIG. 12 is a cross-sectional view showing the configuration of a scanning optical system according to a second embodiment. FIG. 13 is a diagram showing various aberrations of the scanning optical system according to the second embodiment. FIG. 14 is a cross-sectional view showing the configuration of a scanning optical system according to a third embodiment. FIG. 15 is a diagram showing various aberrations of the scanning optical system according to the third embodiment. FIG. 16 is a cross-sectional view showing the configuration of a scanning optical system according to a fourth embodiment. FIG. 17 is a diagram showing various aberrations of the scanning optical system according to the fourth embodiment. FIG. 18 is a cross-sectional view showing the configuration of a scanning optical system according to a fifth embodiment. FIG. 19 is a diagram showing various aberrations of the scanning optical system according to the fifth embodiment. FIG. 19 is a cross-sectional view showing the configuration of a scanning optical system according to a sixth embodiment. FIG. 19 is a diagram showing various aberrations of the scanning optical system according to the sixth embodiment. FIG. 19 is a cross-sectional view showing the configuration of a scanning optical system according to a seventh embodiment. FIG. 19 is a diagram showing various aberrations of the scanning optical system according to the seventh embodiment. FIG. 19 is a cross-sectional view showing the configuration of a scanning optical system according to an eighth embodiment. FIG. 19 is a diagram showing various aberrations of the scanning optical system according to the eighth embodiment. FIG. 19 is a schematic diagram showing a scanning microscope equipped with a scanning optical system. FIG. 20 is a schematic diagram showing a first detector. FIG. 21 is a schematic diagram showing an example of an optical processing device equipped with a scanning optical system. FIG. 21 is a schematic diagram showing an example of an optical processing head. FIG. 22 is a schematic diagram showing an example of an optical measurement device equipped with a scanning optical system. FIG. 23 is a schematic diagram

[0008] A preferred embodiment will be described below. First, a scanning microscope equipped with a scanning optical system according to this embodiment will be described with reference to Figs. 17 and 18. In describing the scanning microscope, the directions indicated by the arrows in Fig. 17 may be referred to as the X direction, Y direction, and Z direction, respectively. The X direction, Y direction, and Z direction are perpendicular to one another. The Z direction is parallel to the optical axis AX of the objective optical system 35.

[0009] [Scanning Microscope] As shown in FIG. 17 , the scanning microscope 1 according to this embodiment includes a stage 10 on which a sample SA is placed, a light source unit 20, an irradiation optical system 30, a light receiving unit 40, and a control unit 60. The stage 10 supports the sample SA, which is the object to be observed. The sample SA may be, for example, a biological sample such as a fluorescently stained cell. If the sample SA is a biological sample, the upper surface of the sample SA may be covered with a cover glass (not shown). Alternatively, a substrate may be used as the sample SA. The substrate used as the sample SA may be a substrate used in the manufacture of a power device (power semiconductor) such as a high electron mobility transistor (HEMT). Such a substrate may have, for example, at least one of a layer made of gallium nitride (GaN), a layer made of C-GaN, and a layer made of aluminum gallium nitride (AlGaN).

[0010] A stage moving unit 11 is provided on the stage 10. The stage moving unit 11 moves the stage 10 in directions perpendicular to the optical axis AX (Z direction) of the objective optical system 35, i.e., in the X and Y directions. By moving the stage 10 in the X and Y directions (directions perpendicular to the optical axis AX of the objective optical system 35) using the stage moving unit 11, the observation area of ​​the sample SA facing the objective optical system 35 can be displaced in the X and Y directions. Note that the observation area is defined as a portion of the sample SA that is scanned by a scanning mechanism 32 (described later) via the objective optical system 35. The observation area may be set to a range narrower than the actual field of view of the scanning microscope 1, or may be set to a range equal to the actual field of view of the scanning microscope 1.

[0011] Furthermore, the stage moving unit 11 can move the stage 10 in a direction along the optical axis AX of the objective optical system 35, i.e., in the Z direction. When the stage moving unit 11 moves the stage 10 in the Z direction, the relative position of the objective optical system 35 with respect to the sample SA supported by the stage 10 changes in the Z direction, and the focal position of the objective optical system 35 on the sample SA changes in the Z direction. By changing the focal position of the objective optical system 35 on the sample SA in the Z direction, it is possible to acquire images of multiple cross sections of the sample SA at different positions in the Z direction (positions along the optical axis AX of the objective optical system 35). Hereinafter, the direction along the optical axis AX of the objective optical system 35 may be referred to as the optical axis direction of the objective optical system 35.

[0012] The light source unit 20 emits irradiation light La toward the irradiation optical system 30. The light source unit 20 includes a light source 21 and a light source lens 22. The light source 21 may be, for example, a laser light source capable of emitting laser light in a predetermined wavelength range. The laser light emitted from the light source 21 is shaped by the light source lens 22 to become parallel light, and is then emitted from the light source unit 20 as irradiation light La. The light source 21 may be a laser light source (e.g., a laser light source that emits a femtosecond laser) that emits pulsed light having a pulse width of less than 1 picosecond (e.g., a pulse width in femtosecond units). The light source 21 is not limited to a laser light source that emits pulsed light, but may also be a laser light source that emits continuous wave light. Furthermore, the light source 21 is not limited to a laser light source, and may be configured using an LED (Light Emitting Diode) or a bright line lamp.

[0013] The wavelength of the illumination light La is selected in a wavelength range (e.g., a wavelength range of 700 nm to 1300 nm) that can excite the fluorescent substance contained in the sample SA or the substances that make up the sample SA to emit light. The wavelength of the illumination light La may also be selected to a wavelength that can excite the fluorescent substance contained in the sample SA or the substances that make up the sample SA by multi-photon excitation to emit light. For example, the wavelength of the illumination light La may be selected to a wavelength that can excite the fluorescent substance contained in the sample SA or the substances that make up the sample SA by two-photon excitation to emit light.

[0014] The irradiation optical system 30 irradiates the sample SA with the irradiation light La emitted from the light source unit 20. The irradiation optical system 30 includes, in order from the light source unit 20 side, a dichroic mirror 31, a scanning mechanism 32, a scanning optical system SL, a first condenser lens 34, and an objective optical system 35. The objective optical system 35 is disposed above the stage 10. The objective optical system 35 faces the sample SA supported by the stage 10. The objective optical system 35 is configured using a plurality of lenses 36 and housed in a lens housing 37. At least some of the plurality of lenses 36 are configured to be movable in the optical axis direction of the objective optical system 35 by rotating a correction collar 38 provided on the lens housing 37. By rotating the correction collar 38 to move at least some of the plurality of lenses 36 in the optical axis direction of the objective optical system 35, aberrations caused by thickness errors in a cover glass (not shown) can be corrected.

[0015] The objective optical system 35 focuses the illumination light La from the scanning mechanism 32 onto an illumination surface RS1 on which the sample SA is placed. The illumination surface RS1 may be set at a position on the surface of the sample SA, or may be set at a position inside the sample SA. Hereinafter, the area on the illumination surface RS1 where the illumination light La is focused to a size approximately equal to the resolution limit of the objective optical system 35 may be referred to as an illumination area 25. The size of the illumination area 25 may be determined by the beam width (e.g., 1 / e 2 The resolution limit of the objective optical system 35 corresponds to the radius of the first dark ring of the so-called Airy disk, and is calculated as 0.61 × λ1 / NA, where λ1 is the wavelength of the irradiating light La and NA is the numerical aperture of the objective optical system 35 (the sine of the opening angle of the irradiating light La emitted from the objective optical system 35). When the size of the irradiated area 25 is smaller than 1.22 × λ1 / NA, which is the diameter of the first dark ring of the Airy disk, the irradiating light La is said to be condensed to the resolution limit.

[0016] 17, the objective optical system 35 is configured using four lenses 36 as an example, but is not limited to this. For example, the objective optical system 35 may be configured using five or more lenses, or may be configured using two or three lenses. Furthermore, instead of or in addition to moving the stage 10 in the Z direction by the stage moving unit 11, the objective optical system 35 may be moved in the Z direction (optical axis direction) to change the focal position of the objective optical system 35 on the sample SA in the Z direction.

[0017] The dichroic mirror 31 has the property of reflecting, for example, blue light or light in a wavelength range shorter than blue light and transmitting light in a wavelength range longer than blue light. The dichroic mirror 31 is not limited to the wavelength characteristics described above, and may have the property of reflecting light generated in the sample SA by multi-photon excitation and transmitting the irradiation light La emitted from the light source unit 20. Hereinafter, the light generated in the sample SA by multi-photon excitation may be referred to as detection light Ld.

[0018] The scanning mechanism 32 scans the irradiation surface RS1 of the sample SA with the irradiation light La from the light source unit 20 in two directions, the X direction and the Y direction. The scanning mechanism 32 is provided with an X-direction deflection mirror 32a and a Y-direction deflection mirror 32b that can change the traveling direction of the irradiation light La. The X-direction deflection mirror 32a and the Y-direction deflection mirror 32b are configured using a galvanometer mirror, a MEMS mirror, a resonant mirror (resonant mirror), or the like. The X-direction deflection mirror 32a and the Y-direction deflection mirror 32b are disposed at a position that is conjugate to the pupil plane Pp of the objective optical system 35 or near a position that is conjugate to the pupil plane Pp of the objective optical system 35. When the X-direction deflection mirror 32a swings or rotates in a rotational direction (θy direction) about the Y axis, the traveling direction of the irradiation light La changes in the θy direction about the Y axis, and the irradiation area 25 on the irradiation surface RS1 moves in the X direction. When the Y-direction deflection mirror 32b oscillates or rotates in a rotational direction (θx direction) around the X-axis, the direction of travel of the irradiation light La changes in the θx direction around the X-axis, and the irradiation area 25 on the irradiated surface RS1 moves in the Y direction.

[0019] Therefore, the scanning mechanism 32 swings or rotates the X-direction deflection mirror 32a and the Y-direction deflection mirror 32b to change the emission direction of the irradiation light La from the light source unit 20, thereby moving the irradiation area 25 on the irradiation surface RS1 (i.e., the focusing position of the irradiation light La) in two directions, the X direction and the Y direction (XY directions). As a result, the scanning optical system SL changes the focusing position of the irradiation light La focused on the irradiation surface RS1 (via the first focusing lens 34 and the objective optical system 35) in accordance with the emission direction of the irradiation light La changed by the scanning mechanism 32, thereby making it possible to two-dimensionally scan the irradiation surface RS1 of the sample SA.

[0020] The scanning optical system SL and the first condenser lens 34 are provided between the scanning mechanism 32 and the objective optical system 35. The scanning optical system SL guides the illumination light La from the scanning mechanism 32 to the objective optical system 35 via the first condenser lens 34. A first intermediate image plane Im1 conjugate with the sample SA (irradiated surface RS1) is formed between the scanning optical system SL and the first condenser lens 34. The scanning optical system SL focuses the illumination light La from the scanning mechanism 32 on the first intermediate image plane Im1. The first intermediate image plane Im1 may also be referred to as the first conjugate plane Im1. The first condenser lens 34 collimates the illumination light La from the scanning optical system SL and guides it to the objective optical system 35. The first condenser lens 34 also focuses the detection light Ld from the objective optical system 35 on the first intermediate image plane Im1. The scanning optical system SL converts the detection light Ld from the first condenser lens 34 into parallel light and guides it to the scanning mechanism 32. Note that the scanning optical system SL and the first condenser lens 34 are not limited to being composed of a single lens, and may be composed of multiple lenses. Details of the scanning optical system SL will be described later. The first condenser lens 34 is also referred to as an imaging lens or a second objective lens.

[0021] The light receiving unit 40 includes a light receiving optical system 41 and a detector 51. The light receiving optical system 41 receives detection light Ld generated in the sample SA (illumination area 25) by multiphoton excitation with the illumination light La, and forms an image 49 of the illumination area 25 of the sample SA on an image plane Imp. The light receiving optical system 41 includes the objective optical system 35 of the illumination optical system 30, a first condenser lens 34, a scanning optical system SL, a scanning mechanism 32, and a dichroic mirror 31. Furthermore, the light receiving optical system 41 includes, in order from the dichroic mirror 31 side (sample SA side), a barrier filter 42, a second condenser lens 43, and a variable magnification optical system 45.

[0022] The barrier filter 42 has a characteristic of transmitting light in a predetermined wavelength range (specifically, the detection light Ld) from the dichroic mirror 31. The barrier filter 42 blocks, for example, at least a portion of the illumination light La reflected by the sample SA, external light, stray light, etc. The barrier filter 42 is also referred to as a bandpass filter. A second intermediate image plane Im2 conjugate with the sample SA (irradiated surface RS1) is formed between the second condenser lens 43 and the variable magnification optical system 45. The second condenser lens 43 condenses the detection light Ld transmitted through the barrier filter 42 onto the second intermediate image plane Im2. The second intermediate image plane Im2 may also be referred to as the second conjugate plane Im2. The second condenser lens 43 is not limited to a single lens, and may be configured using multiple lenses.

[0023] The variable magnification optical system 45 focuses the detection light Ld from the second condenser lens 43 onto an image plane Imp, forming an image 49 of the irradiation area 25 of the sample SA. The sample SA (irradiated surface RS1), the first intermediate image plane Im1, the second intermediate image plane Im2, and the image plane Imp are all conjugate surfaces. The variable magnification optical system 45 is composed of multiple lenses 46 and is held by a zoom lens barrel 48, which has cam grooves and the like, via a holding frame 47. Rotating the zoom lens barrel 48 with an electric motor (not shown) moves at least some of the multiple lenses 46 (in the optical axis direction of the variable magnification optical system 45), changing the focal length and the position of the principal point of the variable magnification optical system 45. This changes the imaging magnification of the variable magnification optical system 45 (i.e., the imaging magnification of the light-receiving optical system 41), changing the size of the image 49 formed on the image plane Imp.

[0024] 17, the variable magnification optical system 45 is configured using four lenses 46 as an example, but is not limited to this. For example, the variable magnification optical system 45 may be configured using five or more lenses, or may be configured using two or three lenses. Also, the detector 51 may be disposed at the second intermediate image plane Im2 without providing the variable magnification optical system 45.

[0025] The detector 51 is configured using, for example, an avalanche photodiode array. The detector 51 has a detection surface 52 with a plurality of detection pixels 53 arranged in a two-dimensional direction (see FIG. 2 ). As an example, the detection surface 52 may have 25 detection pixels 53 arranged in a matrix of five each. The detector 51 is positioned so that the detection surface 52 overlaps with the image plane Imp. As a result, the detection light Ld from the variable magnification optical system 45 is focused on the detection surface 52 of the detector 51 to form an image 49 of the irradiation area 25 of the sample SA. The detector 51 receives the image 49 of the irradiation area 25 of the sample SA formed on the detection surface 52, performs photoelectric conversion, and outputs a light reception signal (also referred to as a detection signal) of the image 49 of the irradiation area 25 of the sample SA. At this time, the detector 51 receives the image 49 of the irradiation area 25 of the sample SA with the plurality of detection pixels 53, performs photoelectric conversion, and outputs a light reception signal corresponding to the light amount of the image 49 of the irradiation area 25 of the sample SA. The detector 51 may be an NDD (Non-Descanned) detector.

[0026] The control unit 60 is configured using, for example, a CPU (Central Processing Unit) or the like. The control unit 60 includes an interface unit 61, a memory unit 65, a data acquisition unit 66, and an image processing unit 67. The control unit 60 controls the operation of the stage movement unit 11, the light source unit 20 (light source 21), the scanning mechanism 32, the correction collar 38 of the objective optical system 35, the electric motor (not shown) of the variable magnification optical system 45, and the like based on a control program stored in the memory unit 65. The interface unit 61 is electrically connected to one end of a network cable NW. The other end of the network cable NW is electrically connected to an external information processing device (not shown).

[0027] The data acquisition unit 66 acquires the light reception signal output from the detector 51. The control unit 60 causes the data acquisition unit 66 to acquire the light reception signal in synchronization with scanning of the sample SA (irradiated surface RS1) by moving the irradiation area 25 in two directions, the X direction and the Y direction (XY directions), using the scanning mechanism 32. The image processing unit 67 generates image data of the sample SA based on the light reception signals output from the multiple detection pixels 53 of the detector 51 acquired by the data acquisition unit 66. The image processing unit 67 may also generate intermediate image data of the sample SA for each detection pixel 53 that outputs a light reception signal among the multiple detection pixels 53 of the detector 51. Then, as disclosed in International Publication No. WO 2022 / 102584, for example, the image processing unit 67 may shift and add the multiple intermediate image data generated for each detection pixel 53 according to the position of the corresponding detection pixel 53 within the detection surface 52 (image plane Imp) to generate image data of the sample SA.

[0028] The image data of the sample SA generated by the image processing unit 67 is transmitted to an external information processing device (not shown) from the interface unit 61 via the network cable NW. The image data of the sample SA generated by the image processing unit 67 may be stored in the storage unit 65. Furthermore, the image of the sample SA generated by the image processing unit 67 may be displayed on a display unit (not shown) provided in the information processing device.

[0029] [Optical Processing Apparatus] The scanning optical system according to this embodiment may be provided not only in a scanning microscope 1 but also in a scanning optical device such as an optical processing apparatus or an optical measurement device. Next, an optical processing apparatus, which is a scanning optical device equipped with the scanning optical system according to this embodiment, will be described with reference to FIGS. 19 and 20 . In the description of the optical processing apparatus, the directions indicated by the arrows in FIG. 19 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are perpendicular to each other. As shown in FIG. 19 , the optical processing apparatus 101 according to this embodiment includes a light source unit 105, a robot arm 110, a transmission optical system 120, and an optical processing head 130. The optical processing apparatus 101 irradiates a workpiece WK placed at a predetermined position (e.g., the upper surface of a stage ST) with processing light Lte under the control of a control device (not shown).

[0030] For example, the processing light Lte irradiated onto the workpiece WK can be used to perform polishing on the workpiece WK. In this case, the optical processing device 101 is used as an optical processing device for performing polishing. The processing light Lte irradiated onto the workpiece WK can also be used to perform cutting on the workpiece WK. In this case, the optical processing device 101 is used as an optical processing device for performing cutting. The processing light Lte irradiated onto the workpiece WK can also be used to perform ablation on the workpiece WK. In this case, the optical processing device 101 is used as an optical processing device for performing ablation.

[0031] The light source unit 105 emits processing light Lte, such as laser light. Note that the processing light Lte may be a type of light other than laser light, as long as it can process the workpiece WK when irradiated onto the workpiece WK. The wavelength range of the processing light Lte may be any wavelength range, as long as it can process the workpiece WK when irradiated onto the workpiece WK. For example, the wavelength range of the processing light Lte may be the wavelength range of visible light, infrared light, or ultraviolet light.

[0032] The robot arm 110 is capable of moving the optical processing head 130 attached to the tip of the robot arm 110 in the X, Y, and Z directions (i.e., three-dimensional directions) under the control of a control device (not shown). The robot arm 110 moves the optical processing head 130 to a position facing an irradiated surface RS2 of the workpiece WK onto which the processing light Lte is irradiated. The irradiated surface RS2 may be set at a position on the surface of the workpiece WK or at a position inside the workpiece WK. The transmission optical system 120 is provided on the robot arm 110. The transmission optical system 120 transmits the processing light Lte emitted from the light source unit 105 to the optical processing head 130.

[0033] The optical processing head 130 is attached to the tip of the robot arm 110. The optical processing head 130 irradiates the workpiece WK with the processing light Lte transmitted by the transmission optical system 120. As shown in FIG. 20 , for example, the optical processing head 130 includes a processing optical system 140, a processing irradiation optical system 150, and a housing 135. The housing 135 houses and holds the processing optical system 140 and the processing irradiation optical system 150. A three-dimensional camera 139 is attached to the housing 135 of the optical processing head 130, and forms a 3D vision capable of recognizing the workpiece WK in three dimensions.

[0034] The processing light Lte transmitted by the transmission optical system 120 is incident on the processing optical system 140. The processing optical system 140 emits the processing light Lte incident on the processing optical system 140 toward the processing irradiation optical system 150. The processing optical system 140 includes a position adjustment optical system 141 and an angle adjustment optical system 142. The position adjustment optical system 141 is capable of adjusting the emission position of the processing light Lte from the processing optical system 140. The position adjustment optical system 141 includes, for example, a parallel plane plate that can be tilted with respect to the traveling direction of the processing light Lte, and the emission position of the processing light is changed by changing the inclination angle of the parallel plane plate. When the emission position of the processing light Lte from the processing optical system 140 changes, the incident angle of the processing light Lte (e.g., the incident angle with respect to the workpiece WK) changes. The angle adjustment optical system 142 is capable of adjusting the emission angle of the processing light Lte from the processing optical system 140. The angle adjustment optical system 142 includes, for example, an angle adjustment mirror that can be tilted with respect to the traveling direction of the processing light Lte, and the emission angle of the processing light is changed by changing the tilt angle of the angle adjustment mirror. When the emission angle of the processing light Lte from the processing optical system 140 changes, the irradiation position of the processing light Lte (for example, the irradiation position on the workpiece WK) changes. Note that the processing optical system 140 does not necessarily have to include at least one of the position adjustment optical system 141 and the angle adjustment optical system 142.

[0035] The processing light Lte emitted from the processing optical system 140 is incident on the processing irradiation optical system 150. The processing irradiation optical system 150 emits the processing light Lte incident on the processing irradiation optical system 150 toward the workpiece WK. The processing irradiation optical system 150 includes a scanning mechanism 151 and a scanning optical system SL. The scanning mechanism 151 is configured using, for example, a galvanometer mirror. The scanning mechanism 151 includes, for example, a scanning mirror whose angle with respect to the optical path of the processing light Lte can be changed. The scanning mechanism 151 changes the emission direction of the processing light Lte by swinging or rotating the scanning mirror to change the angle with respect to the optical path of the processing light Lte. The scanning mechanism 151 is disposed at the position of the pupil between the processing optical system 140 and the scanning optical system SL or at a position near the pupil. Therefore, a change in the emission direction of the processing light Lte by the scanning mechanism 151 is converted by the scanning optical system SL into a change in the irradiation position of the processing light Lte.

[0036] As a result, the scanning optical system SL can two-dimensionally scan the irradiated surface RS2 by changing the irradiation position of the processing light Lte on the irradiated surface RS2, in other words, the focusing position of the processing light Lte focused on the irradiated surface RS2 by the scanning optical system SL, depending on the emission direction of the processing light Lte changed by the scanning mechanism 151. The scanning mechanism 151 shown in FIG. 20 has two scanning mirrors that can rotate around axes along different directions, but it may also have a single scanning mirror that can rotate around an axis that intersects with each other. Furthermore, when the scanning mechanism 151 has two scanning mirrors, an imaging optical system that optically conjugates the two scanning mirrors with each other may be disposed between the two scanning mirrors.

[0037] The processing light Lte emitted from the scanning mechanism 151 is incident on the scanning optical system SL. The scanning optical system SL focuses the processing light Lte from the scanning mechanism 151 onto the irradiation surface RS2 on which the workpiece WK is placed. In other words, the scanning optical system SL irradiates the convergent processing light Lte onto the irradiation surface RS2 of the workpiece WK. The scanning optical system SL is also referred to as an fθ optical system. Details of the scanning optical system SL will be described later.

[0038] The scanning mechanism 151 is configured using a galvanometer mirror or the like, but is not limited to this. For example, the scanning mechanism 151 may be configured using a polygon scanner, an acousto-optical element, or the like. The optical processing device 101 also has a robot arm 110 that can move the optical processing head 130, but is not limited to this. For example, the optical processing device may have a stage on which a workpiece is placed, an optical processing head that irradiates processing light onto the workpiece from above the stage, and a head drive unit that can move the optical processing head above the stage.

[0039] [Optical Measurement Apparatus] Next, an optical measurement apparatus, which is a scanning optical apparatus equipped with a scanning optical system according to this embodiment, will be described with reference to FIGS. 21 and 22 . In the description of the optical measurement apparatus, the directions indicated by the arrows in FIG. 21 may be referred to as the X direction, Y direction, and Z direction, respectively. The X direction, Y direction, and Z direction are perpendicular to one another. The optical measurement apparatus 201 according to this embodiment has the same configuration as the optical processing apparatus 101 described above, except that it includes an optical measurement head 230 instead of the optical processing head 130. Therefore, the same components as those of the optical processing apparatus 101 are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 21 , the optical measurement apparatus 201 according to this embodiment includes a light source unit 105, a robot arm 110, a transmission optical system 120, and the optical measurement head 230. The optical measurement apparatus 201 irradiates a workpiece WK placed at a predetermined position (e.g., the upper surface of a stage ST) with measurement light Ltm under the control of a control device (not shown).

[0040] The light source unit 105 includes multiple measurement light sources 105a and 105b. The multiple measurement light sources 105a and 105b each emit multiple measurement light beams Ltm that are phase-synchronized and coherent with each other. For example, the multiple measurement light sources 105a and 105b may have different oscillation frequencies. Therefore, the multiple measurement light beams Ltm emitted from the multiple measurement light sources 105a and 105b become multiple pulsed light beams with different pulse frequencies (e.g., the number of pulsed light beams per unit time, which is the reciprocal of the emission period of the pulsed light beam). As an example, the first measurement light source 105a may emit measurement light Ltm1 (see FIG. 22) with a pulse frequency of 25 GHz, and the second measurement light source 105b may emit measurement light Ltm2 (see FIG. 22) with a pulse frequency of 25 GHz+α (e.g., +100 kHz).

[0041] The measurement light Ltm may be a type of light other than pulsed light as long as it can measure the workpiece WK by irradiating it on the workpiece WK. The wavelength range of the measurement light Ltm may be any wavelength range as long as it can measure the workpiece WK by irradiating it on the workpiece WK. For example, the wavelength range of the measurement light Ltm may be the wavelength range of visible light, infrared light, or ultraviolet light.

[0042] The robot arm 110 is capable of moving the optical measurement head 230 attached to the tip of the robot arm 110 in the X, Y, and Z directions (i.e., three-dimensional directions) under the control of a control device (not shown). The robot arm 110 moves the optical measurement head 230 to a position facing an irradiation surface RS2 of the workpiece WK onto which the measurement light Ltm is irradiated. The irradiation surface RS2 may be set at a position on the surface of the workpiece WK, or may be set at a position inside the workpiece WK. The transmission optical system 120 transmits the measurement light Ltm emitted from the light source unit 105 to the optical measurement head 230.

[0043] The optical measurement head 230 is attached to the tip of the robot arm 110. The optical measurement head 230 irradiates the workpiece WK with the measurement light Ltm transmitted by the transmission optical system 120. As shown in FIG. 22 , for example, the optical measurement head 230 includes a measurement optical system 240, a measurement irradiation optical system 250, and a housing 235. The housing 235 houses and holds the measurement optical system 240 and the measurement irradiation optical system 250. A three-dimensional camera 239 that forms a 3D vision capable of recognizing the workpiece WK three-dimensionally is attached to the housing 235 of the optical measurement head 230.

[0044] The measurement light Ltm transmitted by the transmission optical system 120 is incident on the measurement optical system 240. The measurement optical system 240 emits the measurement light Ltm incident on the measurement optical system 240 toward the measurement irradiation optical system 250. The measurement optical system 240 includes, for example, a first beam splitter 241, a second beam splitter 242, a first detector 243, a third beam splitter 244, a mirror 245, and a second detector 246.

[0045] The measurement light Ltm transmitted by the transmission optical system 120 is incident on the first beam splitter 241. Specifically, the measurement light Ltm1 from the first measurement light source 105a and the measurement light Ltm2 from the second measurement light source 105b, which are transmitted by the transmission optical system 120, are incident on the first beam splitter 241. The first beam splitter 241 emits the measurement light Ltm1 and the measurement light Ltm2 incident on the first beam splitter 241 toward the second beam splitter 242. The second beam splitter 242 reflects a portion of the measurement light Ltm1, namely, measurement light Ltm1-1, of the measurement light Ltm1 incident on the second beam splitter 242 toward the first detector 243. The second beam splitter 242 transmits the other portion of the measurement light Ltm1 incident on the second beam splitter 242, namely, measurement light Ltm1-2, toward the third beam splitter 244. The second beam splitter 242 reflects a portion of the measurement light Ltm2, that is, measurement light Ltm2-1, of the measurement light Ltm2 incident on the second beam splitter 242, toward the first detector 243. The second beam splitter 242 transmits another portion of the measurement light Ltm2, that is, measurement light Ltm2-2, toward the third beam splitter 244.

[0046] The measurement beam Ltm1-1 and the measurement beam Ltm2-1 reflected by the second beam splitter 242 are incident on the first detector 243. The first detector 243 detects interference light generated by interference between the measurement beam Ltm1-1 and the measurement beam Ltm2-1. Specifically, the first detector 243 detects the interference light by receiving the interference light. Therefore, the first detector 243 may include a light-receiving element (e.g., a photoelectric conversion element) capable of receiving light. The detection result of the first detector 243 is output to a control device (not shown).

[0047] The measurement light Ltm1-2 and the measurement light Ltm2-2 that have passed through the second beam splitter 242 are incident on the third beam splitter 244. The third beam splitter 244 reflects at least a portion of the measurement light Ltm1-2 that has entered the third beam splitter 244 toward a mirror 245. The third beam splitter 244 transmits at least a portion of the measurement light Ltm2-2 that has entered the third beam splitter 244 toward the measurement irradiation optical system 250. The third beam splitter 244 is also referred to as a splitting member.

[0048] The measurement light Ltm1-2 reflected by the third beam splitter 244 is incident on the mirror 245. The measurement light Ltm1-2 incident on the mirror 245 is reflected by the reflecting surface of the mirror 245 (the reflecting surface is also referred to as the reference surface). Specifically, the mirror 245 reflects the measurement light Ltm1-2 incident on the mirror 245 toward the third beam splitter 244. That is, the mirror 245 emits the measurement light Ltm1-2 incident on the mirror 245 as reflected light, that is, measurement light Ltm1-3, toward the third beam splitter 244. The mirror 245 is also referred to as a reference reflecting member. The measurement light Ltm1-3 emitted from the mirror 245 is incident on the third beam splitter 244. The third beam splitter 244 reflects the measurement beams Ltm1-3 incident on the third beam splitter 244 toward the second beam splitter 242. The measurement beams Ltm1-3 reflected by the third beam splitter 244 are incident on the second beam splitter 242. The second beam splitter 242 reflects the measurement beams Ltm1-3 incident on the second beam splitter 242 toward the second detector 246.

[0049] The measurement light Ltm2-2 that passes through the third beam splitter 244 of the measurement optical system 240 is incident on the measurement irradiation optical system 250. The measurement irradiation optical system 250 emits the measurement light Ltm2-2 that has entered the measurement irradiation optical system 250 toward the workpiece WK. The measurement irradiation optical system 250 includes a scanning mechanism 151 and a scanning optical system SL. The scanning mechanism 151 and the scanning optical system SL are configured similarly to the scanning mechanism 151 and the scanning optical system SL of the optical processing apparatus 101 (optical processing head 130). The measurement light Ltm2-2 emitted from the measurement optical system 240 is incident on the scanning mechanism 151. The scanning mechanism 151 changes the emission direction of the measurement light Ltm2-2 by swinging or rotating the scanning mirror to change the angle of the measurement light Ltm2-2 relative to the optical path. The scanning mechanism 151 is disposed at the pupil position between the measurement optical system 240 and the scanning optical system SL or at a position near the pupil. Therefore, a change in the emission direction of the measurement light Ltm2-2 caused by the scanning mechanism 151 is converted into a change in the irradiation position of the measurement light Ltm2-2 by the scanning optical system SL.

[0050] As a result, the scanning optical system SL can two-dimensionally scan the irradiation surface RS2 by changing the irradiation position of the measurement light Ltm2-2 on the irradiation surface RS2, in other words, the focusing position of the measurement light Ltm2-2 focused on the irradiation surface RS2 by the scanning optical system SL, in accordance with the emission direction of the measurement light Ltm2-2 changed by the scanning mechanism 151. The measurement light Ltm2-2 emitted from the scanning mechanism 151 is incident on the scanning optical system SL. The scanning optical system SL focuses the measurement light Ltm2-2 from the scanning mechanism 151 on the irradiation surface RS2 on which the workpiece WK is placed. In other words, the scanning optical system SL irradiates the irradiation surface RS2 of the workpiece WK with the convergent measurement light Ltm2-2.

[0051] When the measurement light Ltm2-2 is irradiated onto the irradiated surface RS2 of the workpiece WK, light resulting from the irradiation of the measurement light Ltm2-2 is generated from the workpiece WK. Examples of light resulting from the irradiation of the measurement light Ltm2-2 include reflected light reflected by the irradiated surface RS2 of the workpiece WK, scattered light scattered by the irradiated surface RS2 of the workpiece WK, and diffracted light diffracted by the irradiated surface RS2 of the workpiece WK. Hereinafter, the light generated from the workpiece WK due to the irradiation of the measurement light Ltm2-2 is referred to as measurement light Ltm2-3. At least a portion of the measurement light Ltm2-3 generated from the workpiece WK due to the irradiation of the measurement light Ltm2-2 is incident on the third beam splitter 244 of the measurement optical system 240 via the scanning optical system SL and the scanning mechanism 151 of the measurement irradiation optical system 250. The third beam splitter 244 transmits at least a portion of the measurement light Ltm2-3 incident on the third beam splitter 244 toward the second beam splitter 242. The second beam splitter 242 reflects at least a portion of the measurement light Ltm2-3 incident on the second beam splitter 242 toward the second detector 246.

[0052] As described above, in addition to the measurement light Ltm2-3, the measurement light Ltm1-3 is incident on the second detector 246. That is, the measurement light Ltm2-3 directed toward the second detector 246 via the workpiece WK, and the measurement light Ltm1-3 directed toward the second detector 246 without passing through the workpiece WK, are incident on the second detector 246. The measurement light Ltm1-3 is also referred to as a reference light. The second detector 246 detects interference light generated by interference between the measurement light Ltm1-3 and the measurement light Ltm2-3. Specifically, the second detector 246 detects the interference light by receiving the interference light. Therefore, the second detector 246 may be provided with a light-receiving element (e.g., a photoelectric conversion element) capable of receiving light. The detection result of the second detector 246 is output to a control device (not shown). Based on the detection results of the first detector 243 and the second detector 246, the control device determines the state of the workpiece WK, such as positional information of the part of the workpiece WK irradiated with the measurement light Ltm2-2 and information about the surface shape (three-dimensional shape) of the workpiece WK.

[0053] The optical measurement device 201 has a robot arm 110 capable of moving the optical measurement head 230, but is not limited to this. For example, the optical measurement device may have a stage on which a workpiece is placed, an optical measurement head that irradiates measurement light onto the workpiece from above the stage, and a head drive unit that can move the optical measurement head above the stage.

[0054] [Scanning Optical System] Next, the scanning optical system SL provided in the scanning optical device, such as the scanning microscope 1 described above, the optical processing apparatus 101, and the optical measurement apparatus 201, will be described. As described above, the scanning optical system SL according to this embodiment scans an illuminated surface with light transmitted through a scanning mechanism that changes the direction of light emitted from a light source. The scanning optical system SL according to this embodiment includes, for example, a first lens group G1 having positive or negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power, as in the scanning optical system SL(1) shown in FIG. 1 . The third lens group G3 includes a lens (L32) whose concave surface faces the illuminated surface.

[0055] With the above configuration, the scanning optical system SL according to this embodiment satisfies the following conditional expressions (1) and (2). 0.007<Σ(nd×tc / νd) / LA<0.021 (1) 1.05<(nd3j-1)×f / (nd3j×r3j)<1.5 (2) where, Σ(nd×tc / νd): the sum of nd×tc / νd of the lenses in the scanning optical system SL, where nd is the refractive index of the lenses constituting the scanning optical system SL at the d-line, tc is the central thickness of the lens, and νd is the Abbe number of the lens at the d-line. LA: the distance on the optical axis from the lens surface on the scanning mechanism side of the lens closest to the scanning mechanism among the lenses constituting the scanning optical system SL to the lens surface on the irradiation surface side of the lens closest to the irradiated surface. nd3j: the refractive index of the lens with the concave surface facing the irradiated surface side. r3j: the radius of curvature of the lens surface on the irradiation surface side of the lens with the concave surface facing the irradiated surface side. f: the focal length of the scanning optical system SL at the t-line.

[0056] According to this embodiment, it is possible to satisfactorily correct field curvature and obtain a bright image. The scanning optical system SL according to this embodiment may be the scanning optical system SL(2) shown in Fig. 3, the scanning optical system SL(3) shown in Fig. 5, or the scanning optical system SL(4) shown in Fig. 7. Furthermore, the scanning optical system SL according to this embodiment may be the scanning optical system SL(5) shown in Fig. 9, the scanning optical system SL(6) shown in Fig. 11, the scanning optical system SL(7) shown in Fig. 13, or the scanning optical system SL(8) shown in Fig. 15.

[0057] Conditional formula (1) defines an appropriate relationship between the sum of nd×tc / νd of the lenses in the scanning optical system SL and the distance on the optical axis from the lens surface closest to the scanning mechanism of the lens constituting the scanning optical system SL that is closest to the scanning mechanism to the lens surface closest to the illuminated surface. Note that the center thickness (tc) of a lens is the distance on the optical axis from the lens surface closest to the scanning mechanism to the lens surface closest to the illuminated surface of the lens.

[0058] Two-photon excitation microscopy (also called multi-photon excitation microscopy) is a known microscopy technique that can achieve nonlinear optical effects at high photon density locations during fluorescence observation. As mentioned above, multi-photon excitation microscopes are configured using scanning microscopes. To achieve high excitation efficiency in multi-photon excitation microscopes, it is necessary to instantaneously increase the photon density by using pulsed laser light as excitation light. It is preferable that the optical pulse of excitation light has a sharp waveform with an extremely narrow pulse width. However, when the optical pulse propagates through a medium with group velocity dispersion (e.g., a lens), the pulse width (time width) of the optical pulse broadens.

[0059] Group velocity dispersion (GVD) is a phenomenon in which the group velocity (the speed at which a group of waves propagates) changes depending on the wavelength. When the wavelength of light is λ, the speed of light is c, and the refractive index of the medium is n(λ), group velocity dispersion GVD is expressed by the following equation (A):

[0060]

[0061] Formula (A) for group velocity dispersion GVD can be found based on the equation for propagation constant k and light frequency ω. The second-order component k2 found from the propagation constant k, i.e., the equation for group velocity dispersion GVD and light frequency ω, is expressed by the following formula (B) (for details on the propagation constant k, see Robert W. Boyd, "Nonlinear Optics Second Edition" (ISBN: 0-12-121682-9), pp. 358-360).

[0062]

[0063] Group velocity dispersion (GVD) multiplied by the center thickness of the lens is called group delay dispersion (GDD). As group delay dispersion (GDD) increases, the pulse width (time width) of the optical pulse widens, reducing the excitation efficiency of multiphoton excitation. For this reason, it has been difficult with conventional multiphoton excitation microscopes to generate multiphoton excitation with high excitation efficiency and obtain bright images.

[0064] In this embodiment, satisfying conditional expression (1) reduces the sum of the center thicknesses of the lenses, thereby shortening the optical path length of light passing through the lenses and reducing group delay dispersion (GDD). Furthermore, satisfying conditional expression (1) reduces the reciprocal of the Abbe number, i.e., the sum of values ​​indicating dispersion, thereby reducing the dispersion of the medium (lens) along the optical path and reducing group delay dispersion (GDD). Thus, satisfying conditional expression (1) reduces group delay dispersion (GDD), thereby enabling multiphoton excitation with high excitation efficiency and producing bright images. Note that setting the upper limit of conditional expression (1) to 0.019 further ensures the effects of this embodiment. Setting the lower limit of conditional expression (1) to 0.011 further ensures the effects of this embodiment.

[0065] Conditional expression (2) defines an appropriate relationship between the refractive index of the lens in the third lens group G3 with its concave surface facing the illuminated surface side at the d-line, the radius of curvature of the lens surface on the illuminated surface side of the lens with its concave surface facing the illuminated surface side, and the focal length of the scanning optical system SL with respect to the t-line. In this embodiment, the radius of curvature of the lens surface is set to a positive value when the center of curvature is located on the illuminated surface side (image surface side). Satisfying conditional expression (2) makes it possible to reduce the Petzval sum and effectively correct field curvature. Note that setting the upper limit of conditional expression (2) to 1.46 can further ensure the effects of this embodiment. Setting the lower limit of conditional expression (2) to 1.12 can further ensure the effects of this embodiment.

[0066] In the scanning optical system SL according to this embodiment, the first lens group G1 may have a meniscus lens L11 that is disposed closest to the scanning mechanism and has its concave surface facing the scanning mechanism side, and may satisfy the following conditional expression (3): −1.5<(nds−1)×f / (nds×rs)<−1.0 (3) where nds is the refractive index of the meniscus lens L11 for the d-line, and rs is the radius of curvature of the lens surface of the meniscus lens L11 that faces the scanning mechanism.

[0067] Conditional expression (3) defines an appropriate relationship between the refractive index of the meniscus lens L11 in the first lens group G1 with respect to the d-line, the radius of curvature of the lens surface of the meniscus lens L11 facing the scanning mechanism, and the focal length of the scanning optical system SL with respect to the t-line. Satisfying conditional expression (3) makes it possible to reduce the Petzval sum and effectively correct field curvature. Setting the upper limit of conditional expression (3) to -1.12 further ensures the effects of this embodiment. Setting the lower limit of conditional expression (3) to -1.45 further ensures the effects of this embodiment.

[0068] In the scanning optical system SL according to this embodiment, the lens of the third lens group G3 having its concave surface facing the illuminated surface side may be included in a cemented meniscus lens CL31 made up of a positive lens and a negative lens cemented with the positive lens, and may satisfy the following conditional expressions (4) and (5): 1.52<nd3p<1.65 (4) 55<νd3p<75 (5) where nd3p is the refractive index of the positive lens in the cemented meniscus lens CL31 for the d-line, and νd3p is the Abbe number of the positive lens in the cemented meniscus lens CL31 for the d-line.

[0069] Conditional expression (4) defines an appropriate range for the refractive index of the positive lens in the cemented meniscus lens CL31 at the d-line. Conditional expression (5) defines an appropriate range for the Abbe number of the positive lens in the cemented meniscus lens CL31 at the d-line. By satisfying conditional expressions (4) and (5), it is possible to ensure the refractive index of the positive lens in the cemented meniscus lens CL31 while reducing the dispersion of the positive lens in the cemented meniscus lens CL31 and thereby reducing the group delay dispersion (GDD). This makes it possible to generate multiphoton excitation with high excitation efficiency and obtain bright images. Furthermore, because the dispersion of the positive lens in the cemented meniscus lens CL31 is reduced, it is possible to suppress the occurrence of chromatic aberration.

[0070] The effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (4) to 1.64. The effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (4) to 1.57. The effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (5) to 70. The effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (5) to 57. The third lens group G3 may include a cemented meniscus lens CL31 in which a positive lens and a negative lens are cemented together in this order from the scanning mechanism side, and the negative lens of the cemented meniscus lens CL31 may be a lens with a concave surface facing the illuminated surface side. The third lens group G3 may also include a positive lens and a negative lens arranged in this order from the scanning mechanism side, and the negative lens may be a lens with a concave surface facing the illuminated surface side.

[0071] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (6): −6.0<f3 / f<−2.0 (6) where f3 is the focal length of the third lens group G3 with respect to the t-line.

[0072] Conditional expression (6) defines an appropriate relationship between the focal length of the third lens group G3 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (6), it is possible to reduce the Petzval sum and to satisfactorily correct field curvature. Note that by setting the upper limit of conditional expression (6) to -2.25, the effect of this embodiment can be made more certain. By setting the lower limit of conditional expression (6) to -5.75, the effect of this embodiment can be made more certain.

[0073] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (7) in addition to the above-mentioned conditional expression (6): 1.0<f2 / f<1.4 (7) where f2 is the focal length of the second lens group G2 with respect to the t-line.

[0074] Conditional expression (7) defines an appropriate relationship between the focal length of the second lens group G2 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (7), it becomes possible to reduce the Petzval sum and to satisfactorily correct the curvature of field.

[0075] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (8): −1.35<f3 / f<−1.0 (8) where f3 is the focal length of the third lens group G3 with respect to the t-line.

[0076] Conditional expression (8) defines an appropriate relationship between the focal length of the third lens group G3 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (8), it is possible to reduce the Petzval sum and to satisfactorily correct field curvature. Note that by setting the upper limit of conditional expression (8) to -1.05, the effect of this embodiment can be made more certain. By setting the lower limit of conditional expression (8) to -1.25, the effect of this embodiment can be made more certain.

[0077] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (9) in addition to the above-mentioned conditional expression (8): 0.6<f2 / f<0.8 (9) where f2 is the focal length of the second lens group G2 with respect to the t-line.

[0078] Conditional expression (9) defines an appropriate relationship between the focal length of the second lens group G2 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (9), it is possible to reduce the Petzval sum and to satisfactorily correct the curvature of field.

[0079] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (10): −6.0<f3 / f<−1.0 (10) where f3 is the focal length of the third lens group G3 with respect to the t-line.

[0080] Conditional expression (10) defines an appropriate relationship between the focal length of the third lens group G3 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (10), it is possible to reduce the Petzval sum and to satisfactorily correct the curvature of field. Note that by setting the upper limit of conditional expression (10) to -1.05, the effect of this embodiment can be made more certain. By setting the lower limit of conditional expression (10) to -5.75, the effect of this embodiment can be made more certain.

[0081] The scanning optical system SL according to this embodiment may satisfy the following conditional expression (11): 0.6<f2 / f<1.4 (11) where f2 is the focal length of the second lens group G2 with respect to the t-line.

[0082] Conditional expression (11) defines an appropriate relationship between the focal length of the second lens group G2 with respect to the t-line and the focal length of the scanning optical system SL with respect to the t-line. By satisfying conditional expression (11), it becomes possible to reduce the Petzval sum and to satisfactorily correct the curvature of field.

[0083] In the scanning optical system SL according to this embodiment, the first lens group G1 may be composed of a single meniscus lens with its concave surface facing the scanning mechanism, or a single cemented meniscus lens with its concave surface facing the scanning mechanism. The third lens group G3 may have a cemented meniscus lens CL31 including a lens with its concave surface facing the illuminated surface, arranged next to the lens in the second lens group G2 closest to the illuminated surface. Alternatively, the third lens group G3 may be composed of a cemented meniscus lens CL31 including a lens with its concave surface facing the illuminated surface.

[0084] Examples of the scanning optical system SL according to the present embodiment will be described below with reference to the drawings. FIGS. 1, 3, 5, 7, 9, 11, 13, and 15 are cross-sectional views showing the configurations and refractive power distributions of scanning optical systems SL (SL(1) to SL(8)) according to Examples 1 to 8. In FIGS. 1, 3, 5, 7, 9, 11, 13, and 15, each lens group is represented by a combination of a letter G and a number, and each lens is represented by a combination of a letter L and a number. In this case, to avoid complication due to the large number and variety of symbols and numbers, each example uses a unique combination of symbols and numbers to represent the lens groups, etc. Therefore, even if the same combination of symbols and numbers is used between examples, this does not necessarily mean that the examples have the same configuration.

[0085] Tables 1 to 8 are shown below, with Table 1 showing data on the various specifications for Example 1, Table 2 for Example 2, Table 3 for Example 3, Table 4 for Example 4, Table 5 for Example 5, Table 6 for Example 6, Table 7 for Example 7, and Table 8 for Example 8. In each example, the t-line (wavelength λ=1013.98 nm) was selected as the reference wavelength for the aberration characteristics.

[0086] In the table of [Overall Specifications], f indicates the focal length of the scanning optical system with respect to the t-line. LA indicates the distance on the optical axis from the lens surface closest to the scanning mechanism of the lens constituting the scanning optical system to the lens surface closest to the irradiated surface of the lens constituting the scanning optical system. nd3j indicates the refractive index of the lens in the third lens group whose concave surface faces the irradiated surface with respect to the d-line. r3j indicates the radius of curvature of the lens surface on the irradiated surface with respect to the concave surface of the lens constituting the scanning optical system whose concave surface faces the irradiated surface with respect to the irradiated surface. nds indicates the refractive index of the meniscus lens in the first lens group with respect to the d-line. rs indicates the radius of curvature of the lens surface of the meniscus lens on the scanning mechanism side. D0 indicates the distance on the optical axis from the scanning mechanism (entrance pupil plane of the scanning optical system) to the lens surface on the scanning mechanism side of the lens closest to the scanning mechanism of the lens constituting the scanning optical system.

[0087] In the [Lens Specifications] table, the surface numbers indicate the order of the optical surfaces from the entrance pupil plane side (scanning mechanism side) along the direction of light beam travel. R indicates the radius of curvature of each optical surface (a surface whose center of curvature is located on the image plane side is a positive value). D indicates the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane). νd indicates the Abbe number based on the d-line of the material of the optical element. nd indicates the refractive index of the material of the optical element with respect to the d-line. The "∞" in the radius of curvature indicates a plane or an aperture. The refractive index of air, nd = 1.00000, is omitted.

[0088] The table of "Lens Group Data" shows the initial surface (the surface closest to the entrance pupil plane) and focal length of each lens group.

[0089] In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0090] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0091] First Example A first example will be described with reference to FIGS. 1 and 2 and Table 1. FIG. 1 is a cross-sectional view showing the configuration of a scanning optical system according to the first example. The scanning optical system SL(1) according to the first example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0092] The position of the entrance pupil plane Pu of the scanning optical system SL(1) corresponds to the position conjugate to the pupil plane Pp of the objective optical system 35 in the scanning microscope 1. As described above, the scanning mechanism 32 of the scanning microscope 1 is disposed at the position of the entrance pupil plane Pu of the scanning optical system SL(1), i.e., at the position conjugate to the pupil plane Pp of the objective optical system 35 (or near the position conjugate to the pupil plane Pp of the objective optical system 35). Furthermore, the position of the entrance pupil plane Pu of the scanning optical system SL(1) corresponds to the position of the pupil between the processing optical system 140 and the scanning optical system SL in the optical processing apparatus 101. As described above, the scanning mechanism 151 of the optical processing apparatus 101 is disposed at the position of the entrance pupil plane Pu of the scanning optical system SL(1), i.e., at the position of the pupil between the processing optical system 140 and the scanning optical system SL (or near the pupil between the processing optical system 140 and the scanning optical system SL). Furthermore, the position of the entrance pupil plane Pu of the scanning optical system SL(1) corresponds to the position of the pupil between the measurement optical system 240 and the scanning optical system SL in the optical measurement device 201. As described above, the scanning mechanism 151 of the optical measurement device 201 is disposed at the position of the entrance pupil plane Pu of the scanning optical system SL(1), that is, the position of the pupil between the measurement optical system 240 and the scanning optical system SL (or a position near the pupil between the measurement optical system 240 and the scanning optical system SL). This also applies to all of the following embodiments.

[0093] The first lens group G1 is composed of a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing a negative meniscus lens L21 with its convex surface facing the entrance pupil plane Pu to a biconvex positive lens L22, and a biconvex positive lens L23. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a cemented meniscus lens CL31 formed by cementing a biconvex positive lens L31 to a biconcave negative lens L32, with its concave surface facing the image plane I side (the illuminated surface side described above). The image plane I, where light from the entrance pupil plane Pu is focused, is located on the image side of the third lens group G3.

[0094] The image plane I corresponds to the first intermediate image plane Im1 in the scanning microscope 1. That is, the image plane I corresponds to a plane conjugate with the irradiated surface RS1 of the sample SA via the objective optical system 35. The image plane I also corresponds to the irradiated surface RS2 of the workpiece WK in the optical processing device 101 and the optical measurement device 201. This also applies to all the following examples. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens with its concave surface facing the image plane I side, i.e., the irradiated surface side.

[0095] Table 1 below lists the values ​​of the specifications of the scanning optical system according to the first embodiment.

[0096] (Table 1) [Overall specifications] f = 60.00 LA = 74.500 nd3j = 1.55298 r3j = 17.295 nds = 1.69930 rs = -19.343 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -19.343 4.500 1.69930 51.11 2 -21.645 25.461 3 246.795 2.000 1.73800 32.26 4 42.317 9.374 1.43875 94.95 5 -88.001 0.200 6 49.287 8.000 1.59522 67.74 7 -524.867 11.964 8 27.555 11.000 1.62846 59.18 9 -375.848 2.000 1.55298 55.07 10 17.295 36.000 [Lens group data] Lens group Initial surface Focal length G1 1 -1293.4 G2 3 69.0 G3 8 -326.6

[0097] FIG. 2 shows various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to the first embodiment. In each aberration diagram in FIG. 2, t indicates the aberrations for the t-line (wavelength λ=1013.98 nm), C indicates the aberrations for the C-line (wavelength λ=656.27 nm), and Ir indicates the aberrations for infrared light with a wavelength λ=1300.00 nm. In the spherical aberration diagram, the vertical axis represents the normalized value, with the maximum value of the entrance pupil radius set to 1, and the horizontal axis represents the aberration value [mm] for each light ray. In the aberration diagram showing field curvature, the solid line represents the sagittal image plane for each wavelength, and the dashed line represents the meridional image plane for each wavelength. In the aberration diagram showing field curvature, the vertical axis represents the image height [mm] and the horizontal axis represents the aberration value [mm]. In the distortion diagram, the vertical axis represents the image height [mm] and the horizontal axis represents the aberration ratio as a percentage (%). In the aberration diagrams of the following examples, the same reference numerals as in this example are used, and overlapping explanations will be omitted.

[0098] From each aberration diagram, it can be seen that the scanning optical system according to Example 1 has excellent optical performance, with various aberrations including field curvature being well corrected.

[0099] Second Example A second example will be described with reference to FIGS. 3 and 4 and Table 2. FIG. 3 is a cross-sectional view showing the configuration of a scanning optical system according to the second example. The scanning optical system SL(2) according to the second example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0100] The first lens group G1 is composed of a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing a biconvex positive lens L21 and a negative meniscus lens L22 with its concave surface facing the entrance pupil plane Pu, a negative meniscus lens L23 with its concave surface facing the entrance pupil plane Pu, and a cemented lens CL22 formed by cementing a biconvex positive lens L24 and a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a cemented meniscus lens CL31 formed by cementing a biconvex positive lens L31 and a biconcave negative lens L32 with its concave surface facing the image plane I (the illuminated surface side). An image plane I where light from the entrance pupil plane Pu is condensed is located on the image side of the third lens group G3. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens with its concave surface facing the image plane I side, i.e., the above-mentioned illuminated surface side.

[0101] Table 2 below lists the values ​​of the specifications of the scanning optical system according to the second embodiment.

[0102] (Table 2) [Overall specifications] f = 60.02 LA = 72.760 nd3j = 1.55298 r3j = 17.099 nds = 1.69680 rs = -17.828 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -17.828 6.500 1.69680 55.53 2 -20.551 15.716 3 544.222 10.525 1.43875 94.95 4 -24.479 2.000 1.60738 56.82 5 -35.602 7.195 6 -33.393 2.000 1.59551 39.24 7 -69.976 0.200 8 47.484 11.000 1.43875 94.95 9 -48.293 2.200 1.57135 52.95 10 -95.880 2.924 11 27.304 10.389 1.62846 59.18 12 -199.190 2.111 1.55298 55.07 13 17.099 37.799 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 -6238.7 G2 3 72.7 G3 11 -317.0

[0103] 4 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 2. From each aberration diagram, it can be seen that the scanning optical system according to Example 2 has excellent optical performance with various aberrations including field curvature well corrected.

[0104] Third Example A third example will be described with reference to FIGS. 5 and 6 and Table 3. FIG. 5 is a cross-sectional view showing the configuration of a scanning optical system according to the third example. The scanning optical system SL(3) according to the third example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0105] The first lens group G1 is composed of a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing a negative meniscus lens L21 with its convex surface facing the entrance pupil plane Pu to a biconvex positive lens L22, a negative meniscus lens L23 with its concave surface facing the entrance pupil plane Pu, and a cemented lens CL22 formed by cementing a biconvex positive lens L24 to a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a cemented meniscus lens CL31 formed by cementing a biconvex positive lens L31 to a biconcave negative lens L32, with its concave surface facing the image plane I (the illuminated surface side). An image plane I where light from the entrance pupil plane Pu is condensed is located on the image side of the third lens group G3. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens with its concave surface facing the image plane I side, i.e., the above-mentioned illuminated surface side.

[0106] Table 3 below lists the values ​​of the specifications of the scanning optical system according to the third embodiment.

[0107] (Table 3) [Overall specifications] f = 60.02 LA = 78.102 nd3j = 1.56883 r3j = 18.063 nds = 1.69680 rs = -17.722 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -17.722 6.500 1.69680 55.53 2 -20.574 20.998 3 194.110 1.800 1.53996 59.46 4 51.303 11.922 1.43875 94.95 5 -31.410 1.344 6 -29.429 2.000 1.61340 44.27 7 -65.383 0.200 8 45.735 11.000 1.43875 94.95 9 -59.608 2.000 1.53996 59.46 10 -137.389 7.837 11 29.948 9.860 1.62846 59.18 12 -122.704 2.640 1.56883 56.36 13 18.063 36.020 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 -2478.6 G2 3 67.2 G3 11 -205.5

[0108] 6 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 3. From each aberration diagram, it can be seen that the scanning optical system according to Example 3 has excellent optical performance, with various aberrations including field curvature being well corrected.

[0109] Fourth Example A fourth example will be described with reference to FIGS. 7 to 8 and Table 4. FIG. 7 is a cross-sectional view showing the configuration of a scanning optical system according to the fourth example. The scanning optical system SL(4) according to the fourth example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0110] The first lens group G1 is composed of a positive meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing together a negative meniscus lens L21 with its convex surface facing the entrance pupil plane Pu, a biconvex positive lens L22, and a negative meniscus lens L23 with its concave surface facing the entrance pupil plane Pu, and a cemented lens CL22 formed by cementing together a biconvex positive lens L24 and a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a biconvex positive lens L31 and a biconcave negative lens L32 with its concave surface facing the image plane I (the illuminated surface side). An image plane I where light from the entrance pupil plane Pu is condensed is located on the image side of the third lens group G3. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens with its concave surface facing the image plane I side, i.e., the above-mentioned illuminated surface side.

[0111] Table 4 below lists the values ​​of the specifications of the scanning optical system according to the fourth embodiment.

[0112] (Table 4) [Overall specifications] f = 60.02 LA = 75.885 nd3j = 1.60738 r3j = 17.807 nds = 1.69680 rs = -19.502 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -19.502 6.500 1.69680 55.53 2 -21.883 23.010 3 135.396 2.000 1.55298 55.07 4 50.338 13.000 1.43875 94.95 5 -27.531 1.800 1.61340 44.27 6 -80.912 0.200 7 45.731 10.401 1.53775 74.70 8 -70.310 1.500 1.53996 59.46 9 -1646.506 4.974 10 27.985 10.500 1.62846 59.18 11 -131.935 2.000 1.60738 56.82 12 17.807 36.031 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 2439.9 G2 3 67.0 G3 10 -180.4

[0113] 8 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 4. From each aberration diagram, it can be seen that the scanning optical system according to Example 4 has excellent optical performance with various aberrations including field curvature well corrected.

[0114] Fifth Example A fifth example will be described with reference to FIGS. 9 and 10 and Table 5. FIG. 9 is a cross-sectional view showing the configuration of a scanning optical system according to the fifth example. The scanning optical system SL(5) according to the fifth example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0115] The first lens group G1 is composed of, in order from the entrance pupil plane Pu side, a negative meniscus lens L11 with a concave surface facing the entrance pupil plane Pu and a positive meniscus lens L12 with a concave surface facing the entrance pupil plane Pu cemented together to form a cemented meniscus lens CL11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, in order from the entrance pupil plane Pu side along the optical axis, a cemented lens CL21 with a biconcave negative lens L21, a biconvex positive lens L22, and a negative meniscus lens L23 with its concave surface facing the entrance pupil plane Pu cemented together, and a cemented lens CL22 with a biconvex positive lens L24 and a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu cemented together. The third lens group G3 is composed of, in order from the entrance pupil plane Pu side, a positive meniscus lens L31 with its concave surface facing the image plane I side (the side of the illuminated surface described above) and a negative meniscus lens L32 with its concave surface facing the image plane I side, cemented together to form a cemented meniscus lens CL31 with its concave surface facing the image plane I side. The image plane I where light from the entrance pupil plane Pu is collected is located on the image side of the third lens group G3. The negative meniscus lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to the lens with its concave surface facing the image plane I side, i.e., the side of the illuminated surface described above.

[0116] Table 5 below lists the values ​​of the specifications of the scanning optical system according to the fifth embodiment.

[0117] (Table 5) [Overall specifications] f = 60.03 LA = 77.208 nd3j = 1.61340 r3j = 19.663 nds = 1.48749 rs = -17.101 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -17.101 1.500 1.48749 70.24 2 -83.709 6.500 1.65100 56.16 3 -22.907 8.789 4 -158.896 1.800 1.70300 52.38 5 40.605 11.626 1.43875 94.95 6 -27.631 1.800 1.57135 52.95 7 -46.125 3.155 8 59.752 10.040 1.49700 81.55 9 -52.149 2.000 1.48749 70.24 10 -86.901 17.498 11 27.302 10.000 1.59319 67.90 12 105.409 2.500 1.61340 44.27 13 19.663 36.020 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 502.3 G2 4 76.6 G3 11 -262.8

[0118] 10 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 5. From each aberration diagram, it can be seen that the scanning optical system according to Example 5 has excellent optical performance, with various aberrations including field curvature being well corrected.

[0119] Sixth Example A sixth example will be described with reference to FIGS. 11 to 12 and Table 6. FIG. 11 is a cross-sectional view showing the configuration of a scanning optical system according to the sixth example. The scanning optical system SL(6) according to the sixth example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0120] The first lens group G1 is composed of, in order from the entrance pupil plane Pu side, a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu and a positive meniscus lens L12 with its concave surface facing the entrance pupil plane Pu cemented together to form a cemented meniscus lens CL11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, in order from the entrance pupil plane Pu side along the optical axis, a cemented lens CL21 with a biconcave negative lens L21 and a biconvex positive lens L22 cemented together, a negative meniscus lens L23 with its concave surface facing the entrance pupil plane Pu, and a cemented lens CL22 with a biconvex positive lens L24 and a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu cemented together. The third lens group G3 is composed of, in order from the entrance pupil plane Pu side, a positive meniscus lens L31 with its concave surface facing the image plane I side (the side of the illuminated surface described above) and a negative meniscus lens L32 with its concave surface facing the image plane I side, cemented together to form a cemented meniscus lens CL31 with its concave surface facing the image plane I side. The image plane I where light from the entrance pupil plane Pu is collected is located on the image side of the third lens group G3. The negative meniscus lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to the lens with its concave surface facing the image plane I side, i.e., the side of the illuminated surface described above.

[0121] Table 6 below lists the values ​​of the specifications of the scanning optical system according to the sixth embodiment.

[0122] (Table 6) [Overall specifications] f = 60.03 LA = 76.322 nd3j = 1.67790 r3j = 19.372 nds = 1.51633 rs = -16.692 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -16.692 1.500 1.51633 64.14 2 -84.286 6.500 1.62041 60.29 3 -21.277 17.333 4 -3292.025 1.800 1.58313 59.37 5 47.391 12.047 1.43875 94.95 6 -28.601 0.832 7 -27.295 2.000 1.61340 44.27 8 -49.996 2.880 9 45.204 10.016 1.43875 94.95 10 -77.264 2.000 1.56384 60.67 11 -135.312 6.914 12 27.415 11.000 1.60300 65.44 13 120.839 1.500 1.67790 55.35 14 19.372 36.031 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 658.4 G2 4 68.5 G3 12 -157.2

[0123] 12 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 6. From each aberration diagram, it can be seen that the scanning optical system according to Example 6 has excellent optical performance, with various aberrations including field curvature being well corrected.

[0124] Seventh Example A seventh example will be described with reference to FIGS. 13 to 14 and Table 7. FIG. 13 is a cross-sectional view showing the configuration of a scanning optical system according to the seventh example. The scanning optical system SL (7) according to the seventh example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0125] The first lens group G1 is composed of a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing a biconcave negative lens L21 and a biconvex positive lens L22 together, a positive meniscus lens L23 with its convex surface facing the entrance pupil plane Pu, and a cemented lens CL22 formed by cementing a negative meniscus lens L24 with its convex surface facing the entrance pupil plane Pu and a biconvex positive lens L25 together. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a cemented meniscus lens CL31 formed by cementing a biconvex positive lens L31 and a biconcave negative lens L32 together, with its concave surface facing the image plane I side (the illuminated surface side). The image plane I, where light from the entrance pupil plane Pu is condensed, is located on the image side of the third lens group G3. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens whose concave surface faces the image plane I side, that is, the above-mentioned illuminated surface side.

[0126] Table 7 below lists the values ​​of the specifications of the scanning optical system according to the seventh embodiment.

[0127] (Table 7) [Overall specifications] f = 60.05 LA = 74.091 nd3j = 1.65412 r3j = 18.911 nds = 1.49782 rs = -17.108 D0 = 41.5 [Lens specifications] Surface number R D νd nd 1 -17.108 6.500 1.49782 82.57 2 -20.384 13.616 3 -900.486 2.000 1.61340 44.27 4 34.458 10.000 1.43875 94.95 5 -64.649 11.348 6 60.728 4.728 1.66382 27.35 7 126.743 0.200 8 51.727 2.000 1.73211 46.18 9 37.497 11.000 1.59522 67.74 10 -131.952 0.200 11 30.855 11.000 1.49700 81.55 12 -464.175 1.500 1.65412 39.68 13 18.911 40.327 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 -625.3 G2 3 46.9 G3 11 -73.3

[0128] 14 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 7. From each aberration diagram, it can be seen that the scanning optical system according to Example 7 has excellent optical performance, with various aberrations including field curvature being well corrected.

[0129] Eighth Example Eighth Example will be described with reference to FIGS. 15 to 16 and Table 8. FIG. 15 is a cross-sectional view showing the configuration of a scanning optical system according to the eighth example. The scanning optical system SL (8) according to the eighth example is composed of, arranged in order from the entrance pupil plane Pu along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0130] The first lens group G1 is composed of a negative meniscus lens L11 with its concave surface facing the entrance pupil plane Pu. The second lens group G2 is composed of, arranged along the optical axis from the entrance pupil plane Pu side, a cemented lens CL21 formed by cementing a positive meniscus lens L21 with its concave surface facing the entrance pupil plane Pu to a negative meniscus lens L22 with its concave surface facing the entrance pupil plane Pu, a biconvex positive lens L23, and a cemented lens CL22 formed by cementing a biconvex positive lens L24 to a negative meniscus lens L25 with its concave surface facing the entrance pupil plane Pu. The third lens group G3 is composed of, arranged from the entrance pupil plane Pu side, a biconvex positive lens L31 and a biconcave negative lens L32 cemented together to form a cemented meniscus lens CL31 with its concave surface facing the image plane I (the illuminated surface side). An image plane I where light from the entrance pupil plane Pu is condensed is located on the image side of the third lens group G3. The negative lens L32 in the cemented meniscus lens CL31 of the third lens group G3 corresponds to a lens with its concave surface facing the image plane I side, i.e., the above-mentioned illuminated surface side.

[0131] Table 8 below lists the values ​​of the specifications of the scanning optical system according to the eighth embodiment.

[0132] (Table 8) [Overall specifications] f = 60.00 LA = 67.097 nd3j = 1.71999 r3j = 17.539 nds = 1.49782 rs = -15.121 D0 = 47.6 [Lens specifications] Surface number R D νd nd 1 -15.121 6.500 1.49782 82.57 2 -17.681 6.026 3 -354.039 13.000 1.45600 91.37 4 -20.079 2.000 1.61720 53.97 5 -60.234 3.832 6 407.066 7.000 1.58144 40.98 7 -126.588 0.100 8 52.975 14.000 1.45600 91.37 9 -42.131 2.000 1.71999 50.27 10 -55.075 0.239 11 26.380 10.100 1.49782 82.57 12 -4968.588 2.300 1.71999 50.27 13 17.539 38.160 [Lens Group Data] Lens Group Initial Surface Focal Length G1 1 -1300.8 G2 3 46.9 G3 11 -64.5

[0133] 16 is a diagram showing various aberrations (spherical aberration, field curvature, and distortion) of the scanning optical system according to Example 8. From each aberration diagram, it can be seen that the scanning optical system according to Example 8 has excellent optical performance with various aberrations including field curvature well corrected.

[0134] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below, which summarizes the values ​​corresponding to the conditional expressions (1) to (11) for all the examples (Examples 1 to 8). Conditional expression (1) 0.007<Σ(nd×tc / νd) / LA<0.021 Conditional expression (2) 1.05<(nd3j-1)×f / (nd3j×r3j)<1.5 Conditional expression (3) -1.5<(nds-1)×f / (nds×rs)<-1.0 Conditional expression (4) 1.52<nd3p<1.65 Conditional expression (5) 55<νd3p<75 Conditional expression (6) -6.0<f3 / f<-2.0 Conditional expression (7) 1.0<f2 / f<1.4 Conditional expression (8) -1.35<f3 / f<-1.0 Conditional expression (9) 0.6<f2 / f<0.8 Conditional expression (10) -6.0<f3 / f<-1.0 Conditional expression (11) 0.6<f2 / f<1.4

[0135] [Values ​​corresponding to conditional expressions] (First to fourth examples) Conditional Expression First Example Second Example Third Example Fourth Example (1) 0.0127 0.0148 0.0136 0.0147 (2) 1.235 1.250 1.205 1.274 (3) -1.277 -1.383 -1.391 -1.264 (4) 1.62846 1.62846 1.62846 1.62846 (5) 59.18 59.18 59.18 59.18 (6) -5.44 -5.28 -3.42 -3.01 (7) 1.15 1.21 1.12 1.12 (8) - - - - (9) - - - - (10) -5.44 -5.28 -3.42 -3.01 (11) 1.15 1.21 1.12 1.12 [Values ​​corresponding to conditional expressions] (Fifth to Eighth Examples) Conditional expression Fifth Example Sixth Example Seventh Example Eighth Example (1) 0.0138 0.0135 0.0166 0.0180 (2) 1.161 1.252 1.256 1.432 (3) -1.150 -1.225 -1.167 -1.319 (4) 1.59319 1.60300 - - (5) 67.90 65.44 - - (6) -4.38 -2.62 - - (7) 1.28 1.14 - - (8) - - -1.22 -1.08 (9) - - 0.78 0.78 (10) -4.38 -2.62 -1.22 -1.08 (11) 1.28 1.14 0.78 0.78

[0136] According to the above-described embodiments, it is possible to realize a scanning optical system, a scanning microscope, and a scanning optical device that can effectively correct various aberrations including field curvature and obtain bright images.

[0137] Here, the above examples show specific examples of this embodiment, and this embodiment is not limited to these.

[0138] At least some of the components of the above-described embodiments can be appropriately combined with at least some other components of the above-described embodiments. Some of the components of the above-described embodiments may not be used.

[0139] The present invention is not limited to the above-described embodiments, but can be modified as appropriate within the scope of the claims and the gist or concept of the invention as can be read from the entire specification, and scanning optical systems, scanning microscopes, and scanning optical devices incorporating such modifications are also included in the technical scope of the present invention.

[0140] SL: Scanning optical system G1: First lens group G2: Second lens group G3: Third lens group

Claims

1. A scanning optical system that scans an illuminated surface with light via a scanning mechanism that changes the emission direction of light from a light source, the optical system has, arranged in order from the scanning mechanism side, a first lens group having positive or negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power; the third lens group has a lens having a concave surface facing the illuminated surface side, A scanning optical system that satisfies the following conditional expression: 0.007<Σ(nd×tc / νd) / LA<0.021 1.05<(nd3j-1)×f / (nd3j×r3j)<1.5 where Σ(nd×tc / νd) is the sum of nd×tc / νd of the lenses in the scanning optical system, where nd is the refractive index of the lenses constituting the scanning optical system with respect to the d-line, tc is the center thickness of the lenses, and νd is the Abbe number of the lenses with respect to the d-line. LA: the distance on the optical axis from the lens surface of the lens closest to the scanning mechanism among the lenses constituting the scanning optical system, on the side of the scanning mechanism, to the lens surface of the lens closest to the illuminated surface, on the side of the illuminated surface nd3j: refractive index for the d line of the lens with the concave surface facing the illuminated surface side r3j: the radius of curvature of the lens surface on the side of the irradiated surface of the lens whose concave surface faces the side of the irradiated surface f: focal length of the scanning optical system with respect to the t-line

2. the first lens group includes a meniscus lens arranged closest to the scanning mechanism and having a concave surface facing the scanning mechanism; 2. The scanning optical system according to claim 1, wherein the following condition is satisfied: -1.5<(nds-1)×f / (nds×rs)<-1.0 where nds is the refractive index of the meniscus lens at the d line rs: radius of curvature of the lens surface of the meniscus lens on the side of the scanning mechanism

3. the lens in the third lens group having a concave surface facing the illuminated surface side is included in a cemented meniscus lens including a positive lens and a negative lens cemented with the positive lens, 2. The scanning optical system according to claim 1, wherein the following condition is satisfied: 1.52<nd3p<1.65 55<νd3p<75 where nd3p is the refractive index of the positive lens in the cemented meniscus lens with respect to the d-line. νd3p: Abbe number of the positive lens in the cemented meniscus lens relative to the d-line

4. 2. The scanning optical system according to claim 1, wherein the following condition is satisfied: -6.0<f3 / f<-2.0 where f3 is the focal length of the third lens group with respect to the t-line.

5. 5. The scanning optical system according to claim 4, wherein the following condition is satisfied: 1.0<f2 / f<1.4 where f2 is the focal length of the second lens group with respect to the t-line.

6. 2. The scanning optical system according to claim 1, wherein the following condition is satisfied: -1.35<f3 / f<-1.0 where f3 is the focal length of the third lens group with respect to the t-line.

7. 7. The scanning optical system according to claim 6, wherein the following condition is satisfied: 0.6<f2 / f<0.8 where f2 is the focal length of the second lens group with respect to the t-line.

8. the first lens group is composed of one meniscus lens with a concave surface facing the scanning mechanism side, or one cemented meniscus lens with a concave surface facing the scanning mechanism side, 2. The scanning optical system according to claim 1, wherein the third lens group has a cemented meniscus lens including a lens with a concave surface facing the illuminated surface, arranged next to the lens in the second lens group closest to the illuminated surface.

9. a scanning mechanism that changes the direction of light emitted from the light source; an objective optical system that focuses light from the scanning mechanism onto an irradiated surface on which a sample is placed; a scanning optical system according to any one of claims 1 to 8, which is provided between the scanning mechanism and the objective optical system and guides light from the scanning mechanism to the objective optical system; The scanning optical system is a scanning microscope that scans the illuminated surface by changing the focusing position of the light focused on the illuminated surface in accordance with the emission direction of the light changed by the scanning mechanism.

10. a scanning mechanism that changes the direction of light emitted from the light source; and a scanning optical system according to any one of claims 1 to 8, The scanning optical system is a scanning optical device that scans the illuminated surface by changing the focusing position of the light focused on the illuminated surface in accordance with the emission direction of the light changed by the scanning mechanism.