Luminaire and microscope

Abstract

To provide a luminaire capable of effectively using light emitted from a light source.SOLUTION: A luminaire 100 comprises a light source 110 and a lighting optical system 120 which lights up a sample with light from the light source 110, wherein the light source 110 is arranged along the optical axis AX1 of the lighting optical system 120 which has an optical member 121 that the light from the light source 110 impinges on, and is provided with a meta-lens 123 for lighting, converting the light from the light source 110 having impinged on the optical member 121 into substantially parallel light, on the surface of the optical member 121 on the opposite side from the light source 110.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an illumination device and a microscope. [Background technology]

[0002] Conventionally, various illumination devices for microscopes have been proposed (for example, see Patent Document 1). In such illumination devices, it is required to effectively utilize the light emitted from the light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5018192 Summary of the Invention

[0004] An illumination device according to the present invention includes a light source and an illumination optical system that illuminates with light from the light source, the light source being arranged along an optical axis of the illumination optical system, the illumination optical system having an optical element into which light from the light source is incident, and an illumination metalens that converts the light from the light source that has been incident on the optical element into approximately parallel light is provided on a surface of the optical element opposite to the light source side, and the illumination device satisfies the following conditional formula: 0≦DA / DB≦0.1 where DA is the distance on the optical axis from the light source to the surface of the optical member facing the light source. DB: the distance on the optical axis from the light source to the surface of the optical member opposite to the light source side

[0005] A microscope according to the present invention includes the above-described illumination device for illuminating a sample, and an observation optical system for receiving light from the sample. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of a microscope. [Diagram 2] FIG. 2 is a schematic diagram showing the optical structure of a microscope. [Diagram 3] 1 is a cross-sectional view showing a configuration of an illumination device according to a first embodiment. [Figure 4] 1 is a diagram showing optical paths of an illumination optical system according to a first embodiment. [Diagram 5] FIG. 2 is a close-up view of an example metalens surface. [Figure 6] FIG. 13 is a schematic diagram showing a modified example of the illumination optical system. [Figure 7] FIG. 11 is a cross-sectional view showing a configuration of an illumination device according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing optical paths of an illumination optical system according to a second embodiment. [Figure 9] FIG. 2 is an explanatory diagram relating to an image height on a Fourier plane. [Figure 10] FIG. 11 is a cross-sectional view showing a configuration of an illumination device according to a modified example of the second embodiment. [Figure 11] 1 is a graph showing transmittance characteristics versus incident angle of a light-transmitting member. [Figure 12] 13 is a graph showing another example of transmittance characteristics with respect to the angle of incidence of a light-transmitting member. [Figure 13] FIG. 11 is a cross-sectional view showing a configuration of an illumination device according to a third embodiment. [Figure 14] FIG. 11 is a diagram showing optical paths of an illumination optical system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Preferred embodiments of the present invention will be described below. First, a microscope equipped with an illumination device according to each embodiment will be described. As shown in Figs. 1 and 2, a microscope 1 includes a stage 5, an observation optical system 10, an illumination device 100, an imaging optical system 60, and a camera. A sample SA to be observed is placed on the stage 5. An observation lens is provided at the center of the stage 5. An observation hole (not shown) is provided in the stage 5. Through the observation hole in the stage 5, the sample SA can be illuminated and observed from below the stage 5. In addition, the stage 5 may be provided with a stage drive unit (not shown) capable of moving the stage 5 in the horizontal direction and the up-down direction.

[0008] The observation optical system 10 forms an image IM of the sample SA. The observation optical system 10 has, arranged in order from the sample SA side, an objective lens 11, a filter cube 21, an imaging lens 26, a first reflecting mirror 31, a first relay lens 41, a second reflecting mirror 32, a second relay lens 42, a third relay lens 43, and a third reflecting mirror 33. An eyepiece lens 50 is disposed on the image side of the observation optical system 10. In addition, a prism 61 of an imaging optical system 60 is removably inserted on the optical path between the imaging lens 26 and the first reflecting mirror 31.

[0009] The objective lens 11 is attached to the revolver 13 in a state facing upward, and is disposed below the stage 5. This allows the objective lens 11 to face the sample SA on the stage 5 through an observation hole (not shown) in the stage 5. A plurality of objective lenses 11 having different magnifications and pupil diameters are attached to the revolver 13.

[0010] The filter cube 21 has an excitation filter 22, a dichroic mirror 23, and an absorption filter 24. The excitation filter 22 has a property of selectively transmitting light (excitation light) in a band that causes the sample SA to fluoresce, and blocking light in other bands. The dichroic mirror 23 reflects the illumination light (excitation light) that has passed through the illumination relay lens 130 of the illumination device 100 and the excitation filter 22 toward the objective lens 11. The dichroic mirror 23 transmits observation light, such as fluorescence, generated from the sample SA. This allows the illumination optical system 120 to illuminate or excite the sample SA from the same side as the objective lens 11. The absorption filter 24 has a property of transmitting the fluorescence (observation light) generated from the sample SA, and blocking light in bands other than the fluorescence generated from the sample SA.

[0011] The imaging lens 26 receives the fluorescence (observation light) from the objective lens 11 that has passed through the absorption filter 24 and forms an intermediate image IMa of the sample SA. The first reflecting mirror 31 reflects the fluorescence that has passed through the imaging lens 26 toward the first relay lens 41. The second reflecting mirror 32 reflects the fluorescence that has passed through the first relay lens 41 toward the second relay lens 42. The third reflecting mirror 33 reflects the fluorescence that has passed through the second relay lens 42 and the third relay lens 43 toward the eyepiece 50. The first relay lens 41, the second relay lens 42, and the third relay lens 43 relay the intermediate image IMa of the sample SA formed by the imaging lens 26 and form an image IM of the sample SA. A user of the microscope 1 uses the eyepiece 50 to observe the image IM of the sample SA.

[0012] The illumination device 100 illuminates the sample SA on the stage 5 through an observation hole (not shown) of the stage 5. The illumination device 100 includes a light source 110, an illumination optical system 120, and an illumination relay lens 130, which are arranged in this order from the light source side. The illumination device 100 further includes a filter cube 21 and an objective lens 11. Details of the illumination device 100 (the light source 110, the illumination optical system 120, and the illumination relay lens 130) will be described later.

[0013] The imaging optical system 60 includes, arranged in order from the sample SA side, an objective lens 11, a filter cube 21, and an imaging lens 26. The imaging optical system 60 further includes a prism 61 and a camera relay lens 62. The prism 61 is removably inserted into the optical path between the imaging lens 26 and the first reflecting mirror 31. The prism 61 reflects the fluorescence (observation light) that has passed through the imaging lens 26 toward the camera relay lens 62. The camera relay lens 62 guides the fluorescence reflected by the prism 61 to a camera 70, which forms an image of the sample SA (not shown). The camera 70 is a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) The image sensor is made up of an image sensor (imaging element) such as a CdTeOxide Semiconductor. The camera 70 converts the image of the sample SA formed by the camera relay lens 62 into an electrical signal and outputs it.

[0014] Next, an illumination device 100 according to the first embodiment will be described. Fig. 3 is a schematic diagram of the illumination device 100 according to the first embodiment. As shown in Fig. 3, the illumination device 100 according to the first embodiment includes a light source 110, an illumination optical system 120, an illumination relay lens 130, and a condenser lens 140, which are arranged in this order from the light source side. In Fig. 3, the filter cube 21 and the objective lens 11 included in the illumination device 100 are shown as the condenser lens 140.

[0015] The light source 110 is a solid-state light source such as a light-emitting diode (LED). The solid-state light source is a solid-state device that supplies energy such as electricity to a solid (substance) and emits light specific to the substance when excited. The light source 110 is not limited to a light-emitting diode (LED), and may be a solid-state light source such as a semiconductor laser (LD) or an organic electroluminescence (OEL). The light source 110 emits, as illumination light, light (excitation light) in a band that causes fluorescence in the sample SA. The light source 110 is arranged along an optical axis AX1 of the illumination optical system 120. The light source 110 may be arranged adjacent to a surface of the optical member 121 on the light source 110 side.

[0016] The illumination optical system 120 irradiates illumination light emitted from the light source 110 onto a predetermined illumination surface SR of the sample SA via an illumination relay lens 130 and a condenser lens 140 (filter cube 21 and objective lens 11). The illumination optical system 120 has an optical member 121, a fly's eye integrator 125, a collector lens 127, and a field stop FS1, which are arranged in this order from the light source 110 side along the optical axis AX1.

[0017] Illumination light emitted from the light source 110 is incident on the optical member 121. The optical member 121 is formed in a flat plate shape using a light-transmitting optical material such as glass or resin. The optical material of the optical member 121 has a refractive index of 1. For example, the optical material of the optical member 121 may be silica glass (refractive index nIR=1.45 at the illumination wavelength), sapphire glass (refractive index nIR=1.76 at the illumination wavelength), or PMMA (methacrylic resin: refractive index nIR=1.48 at the illumination wavelength).

[0018] As also shown in FIG. 4, the lighting metalens 123 is provided on the surface of the optical member 121 opposite to the light source 110 side. The lighting metalens 123 is configured by forming a metalens surface ML1 of a predetermined structure on one surface (the surface opposite to the light source 110 side) of, for example, a thin plate-shaped substrate (not shown). The lighting metalens 123 may be bonded to the surface of the optical member 121 opposite to the light source 110 side, or may be formed integrally with the optical member 121. The metalens surface ML1 has a nanostructure (a structure in which nano-sized cells are arranged in a pattern) that modulates the phase, polarization, and / or amplitude of the wavelength of the incident light. The nanostructure of the metalens surface ML1 allows the lighting metalens 123 to change the wavefront of the light transmitted through the lighting metalens 123 so that it differs from the wavefront of the light incident on the lighting metalens 123. That is, the nanostructure makes it possible to control the amount of phase shift of the light, etc., and change the behavior of the light. In the first embodiment, illumination metalens 123 (metalens surface ML1) is designed so as to convert the light from light source 110 that is incident on optical member 121 into substantially parallel light.

[0019] Note that "approximately parallel light" refers to a state of light that is nearly parallel with an angle of about 0 degrees to 5 degrees with respect to the optical axis AX1. "Approximately parallel light" includes weakly converging light and weakly diverging light. If the angle with respect to the optical axis AX1 is up to about 5 degrees, it can be considered as parallel light in terms of optical design.

[0020] FIG. 5 shows an example of the metalens surface ML1. In the metalens surface ML1 shown in FIG. 5, a plurality of fine columnar projections are formed on amorphous silicon by electron beam lithography. By changing the size of these columnar projections within the surface, a desired phase distribution can be obtained. The structure of the metalens surface is also called a metalens structure, and refers to a structure that has a light-collecting effect by utilizing phase modulation due to a fine structure. The structure of the metalens surface ML1 shown in FIG. 5 is a waveguide-type metalens structure, but is not limited to this, and may be a micro-post-type metalens structure. In addition, the cross-sectional shape of the columnar projections may be a circle, a triangle, a square, a rectangle, a parallelogram, a regular hexagon, a polygon, a non-polygon, an ellipse, a hollow rectangle, a hollow circle, or the like, in addition to the rectangle shown in FIG. 5.

[0021] The material of the microstructure is amorphous silicon ( Although amorphous silicon is exemplified, other materials such as crystalline silicon and polycrystalline silicon may be used. The material of the microstructure may be the following oxides, for example, oxides of aluminum (Al2O3, etc.), oxides of silicon (SiO2, etc.), oxides of hafnium (HfO2, etc.), oxides of zinc (ZnO, etc.), oxides of magnesium (MgO, etc.), and oxides of titanium (TiO2, etc.). The material of the microstructure may be the following nitrides, for example, nitrides of silicon (Si3N4, etc.), nitrides of boron (BN, etc.), and nitrides of tungsten (WN, etc.). The material of the microstructure may be sulfides, GaP, GaAs, AlSb, AlAs, AlGaAs, AlGaInP, BP, pure elements, etc. In addition, although electron beam lithography is exemplified as a method for manufacturing the microstructure, other methods such as optical lithography, nanoimprinting, and resist etching may be used.

[0022] The fly's eye integrator 125 has a plurality of unit lenses (not shown) arranged two-dimensionally in a plane perpendicular to the optical axis AX1 of the illumination optical system 120. A detailed configuration of the fly's eye integrator 125 is described in, for example, Japanese Patent No. 5018192. A small light source image that emits illumination light for each unit lens is formed on the exit surface of the fly's eye integrator 125. The exit surface of the fly's eye integrator 125 is arranged at the front focal position (the focal position on the light source 110 side) of the collector lens 127. The collector lens 127 converts the illumination light emitted from each unit lens of the fly's eye integrator 125 into parallel light. The field stop FS1 is arranged at the rear focal position (the focal position on the opposite side to the light source 110 side) of the collector lens 127.

[0023] The illumination relay lens 130 (and the condenser lens 140) are arranged side by side along the optical axis AX1 of the illumination optical system 220. The illumination relay lens 130 condenses the illumination light that has passed through the field stop FS1 of the illumination optical system 120 toward the aperture stop AS1 that is arranged at the front focal position of the condenser lens 140 (objective lens 11). As a result, the above-mentioned light source image is formed on the plane where the aperture stop AS1 is arranged.

[0024] Illumination light emitted from light source 110 is incident on optical member 121 of illumination optical system 120. The illumination light incident on optical member 121 passes through optical member 121 and enters illumination metalens 123. The illumination light transmitted through illumination metalens 123 (metalens surface ML1) becomes parallel light and enters fly's eye integrator 125. Illumination light emitted from each unit lens (not shown) of fly's eye integrator 125 passes through collector lens 127 and becomes parallel light, passes through field stop FS1, and enters illumination relay lens 130. The light transmitted through illumination relay lens 130 passes through aperture stop AS1 and condenser lens 140 (filter cube 21 and objective lens 11) and is irradiated onto illumination surface SR.

[0025] In the first embodiment, an illumination metalens 123 is provided on the surface of the optical member 121 opposite to the light source 110. The illumination metalens 123 is a metalens that reflects light incident on the optical member 121. The light from the light source 110 is made to be approximately parallel. This allows the illumination light emitted from the light source 110 to be parallel and incident on the fly's eye integrator 125, even if a reflecting member or the like that collects the light from the light source is not arranged around the light source. This makes it possible to effectively utilize the light emitted from the light source 110, and also allows the illumination device 100 (and the microscope 1) to be made compact.

[0026] In the illumination device 100 according to the first embodiment, the following conditional expression (1) may be satisfied. 0≦DA / DB≦0.1 (1) where DA is the distance on the optical axis from the light source 110 to the surface of the optical member 121 on the light source 110 side. DB: Distance on the optical axis from the light source 110 to the surface of the optical member 121 opposite to the light source 110 side

[0027] Conditional formula (1) specifies an appropriate relationship between a distance DA (see, for example, FIG. 6) on the optical axis from the light source 110 to a surface of the optical member 121 on the light source 110 side, and a distance DB (see, for example, FIG. 6) on the optical axis from the light source 110 to a surface of the optical member 121 on the opposite side to the light source 110 side. By satisfying conditional formula (1), it is possible to fill the space between the light source 110 and the illumination metalens 123 with a medium (optical material such as glass or resin) having a refractive index higher than that of air. Therefore, more light (specifically, light corresponding to a numerical aperture (NA) of 0.95 or more) of the light emitted from the light source 110 can be incident on the illumination metalens 123 as illumination light. Therefore, the light emitted from the light source 110 can be effectively utilized.

[0028] In the illumination device 100 according to the first embodiment, the light source 110 is disposed adjacent to the surface of the optical member 121 on the light source 110 side, and may satisfy the following conditional formula (1-1). DA / DB=0 (1-1)

[0029] Conditional formula (1-1) is the same as the above-mentioned conditional formula (1). By satisfying conditional formula (1-1), like the above-mentioned conditional formula (1), it is possible to effectively utilize the light emitted from the light source 110.

[0030] Furthermore, the light source 110 may be a chip LED, and the surface of the optical member 121 facing the light source 110 may be a flat surface. The chip LED is also called a surface-mounted LED. This allows the area in which the light source 110 and the optical member 121 are in close proximity to each other to be increased. Therefore, more light (specifically, light equivalent to a numerical aperture (NA) of 0.95 or more) of the light emitted from the light source 110 can be made incident on the illumination metalens 123 as illumination light. Therefore, the light emitted from the light source 110 can be effectively utilized.

[0031] The light source 110 does not have to be disposed adjacent to the surface of the optical member 121 on the light source 110 side. For example, as shown in Fig. 6, the light source 110 may be disposed at a distance (DA) from the surface of the optical member 121 on the light source 110 side. In this case, the conditional formula (1) may be satisfied as described above.

[0032] Next, an illumination device 200 according to a second embodiment will be described. Fig. 7 is a schematic diagram of the illumination device 200 according to the second embodiment. As shown in Fig. 7, the illumination device 200 according to the second embodiment includes a light source 210, an illumination optical system 220, an illumination relay lens 230, and a condenser lens 240, which are arranged in this order from the light source side. In Fig. 7, the filter cube 21 and the objective lens 11 included in the illumination device 200 are shown as the condenser lens 240, as in the first embodiment.

[0033] The light source 210 is a solid-state light source such as a light-emitting diode (LED). In the second embodiment, the light distribution of the light source 210 is a Lambertian light distribution. The light source 210 is not limited to a light-emitting diode (LED), and may be a solid-state light source such as a semiconductor laser (LD) or an organic electroluminescence (OEL) as long as it has a Lambertian light distribution characteristic. The light source 210 emits, as illumination light, for example, light (excitation light) in a band that causes fluorescence in the sample SA. The light source 210 is arranged along the optical axis AX2 of the illumination optical system 220. The light source 210 may be arranged adjacent to a surface of the optical member 220 on the light source 210 side.

[0034] The illumination optical system 220 irradiates illumination light emitted from the light source 210 onto a predetermined illumination surface SR of the sample SA via an illumination relay lens 230 and a condenser lens 240 (filter cube 21 and objective lens 11). The illumination optical system 220 has an optical member 221 and a field stop FS2, which are arranged in order from the light source 210 side along the optical axis AX2.

[0035] Illumination light emitted from the light source 210 is incident on the optical member 221. The optical member 221 is configured in the same manner as the optical member 121 according to the first embodiment. As also shown in FIG. 8, an illumination metalens 223 is provided on the surface of the optical member 221 opposite to the light source 210 side. The illumination metalens 223 is configured by forming a metalens surface ML2 having a predetermined structure on one surface (the surface opposite to the light source 210 side) of a thin plate-like substrate (not shown), for example. The illumination metalens 223 may be bonded to the surface of the optical member 221 opposite to the light source 210 side, or may be formed integrally with the optical member 221. The metalens surface ML2 has a metalens structure similar to the metalens surface ML1 according to the first embodiment. In the second embodiment, the illumination metalens 223 (metalens surface ML2) is designed so as to convert the light from the light source 210 incident on the optical member 221 into approximately parallel light.

[0036] The field stop FS2 is disposed at the rear focal position (the focal position on the opposite side to the light source 210) of the illumination metalens 223. The illumination relay lens 230 (and the condenser lens 240) are disposed side by side along the optical axis AX2 of the illumination optical system 220. The illumination relay lens 230 collects the illumination light that has passed through the field stop FS2 of the illumination optical system 220, toward the aperture stop AS2 that is disposed at the front focal position of the condenser lens 240 (objective lens 11).

[0037] Illumination light emitted from light source 210 is incident on optical member 221 of illumination optical system 220. The illumination light incident on optical member 221 transmits through optical member 221 and enters illumination metalens 223. The illumination light transmitted through illumination metalens 223 (metalens surface ML2) becomes approximately parallel light, passes through field stop FS2, and enters illumination relay lens 230. The light transmitted through illumination relay lens 230 passes through aperture stop AS2 and condenser lens 240 (filter cube 21 and objective lens 11) and is irradiated onto illumination surface SR.

[0038] In the second embodiment, an illumination metalens 223 is provided on the surface of optical member 221 opposite to the light source 210 side. Illumination metalens 223 converts the light from light source 210 that is incident on optical member 221 into substantially parallel light and causes it to be incident on illumination relay lens 230. This makes it possible to collimate the illumination light emitted from light source 210 and irradiate illumination surface SR without, for example, arranging a reflecting member that collects light from the light source or the above-mentioned fly's eye integrator and collector lens. This makes it possible to effectively utilize the light emitted from light source 210 and also makes it possible to make illumination device 200 (and microscope 1) more compact.

[0039] 9, the image height at Fourier plane FR that passes through the rear focal point of illumination metalens 223 and is perpendicular to the optical axis AX2 of illumination optical system 220 is defined as h (unit: mm), and the divergence angle of light source 210, which is a solid-state light source, is defined as θ. Furthermore, the focal length of illumination metalens 223 is defined as fm (unit: mm).

[0040] In the illumination device 200 according to the second embodiment, the following conditional expression (2) may be satisfied. h = fm × sinθ (2)

[0041] When the light distribution of light source 210 is a Lambertian light distribution, the illuminance distribution of the illumination light can be made uniform by designing illumination metalens 223 (metalens surface ML2) so as to satisfy conditional formula (2). The luminous flux Pe of the illumination light is expressed as Pe=α×cosθ×dθ, where α is a coefficient. When conditional formula (2) is differentiated with respect to θ, dh=f×cosθ×dθ. The area ds at the position of image height h on the Fourier plane FR is proportional to dh. The illuminance E of the illumination light is E=Pe / ds=(α×cosθ×dθ) / (f×cosθ×dθ)=α / f=constant.

[0042] In the illumination device 200 according to the second embodiment, the above-mentioned conditional formula (1) may be satisfied, as in the first embodiment. By satisfying the conditional formula (1), the light emitted from the light source 210 can be effectively utilized, as in the first embodiment.

[0043] In the illumination device 200 according to the second embodiment, the above-mentioned conditional formula (1-1) may be satisfied, as in the first embodiment. By satisfying the conditional formula (1-1), the light emitted from the light source 210 can be effectively utilized, as in the case of the above-mentioned conditional formula (1).

[0044] Furthermore, the light source 210 may be a chip LED, and the surface of the optical member 221 facing the light source 210 may be a flat surface. This makes it possible to effectively utilize the light emitted from the light source 210, similar to the first embodiment.

[0045] The light source 210 does not have to be disposed adjacent to the surface of the optical member 221 on the light source 210 side. As described in the first embodiment, the light source 210 may be disposed at a distance (DA) from the surface of the optical member 221 on the light source 210 side.

[0046] In the second embodiment described above, for example, as in the lighting device 200A shown in FIG. 10, a light-transmitting member 260 capable of transmitting light emitted from the lighting metalens 223 may be provided between the lighting metalens 223 and the lighting relay lens 230 of the lighting optical system 220. The light-transmitting member 260 may be provided between the field stop FS2 (Fourier plane FR) of the lighting optical system 220 and the lighting relay lens 230, or may be provided between the lighting metalens 223 and the field stop FS2. The light-transmitting member 260 has a characteristic that the transmittance is relatively high when the angle of incidence of light to the light-transmitting member 260 is small, and the transmittance is relatively low when the angle of incidence of light to the light-transmitting member 260 is large. That is, the transmittance of the light-transmitting member 260 decreases as the angle of incidence of light to the light-transmitting member 260 increases.

[0047] When the size of the columnar protrusions constituting the metalens surface ML2 deviates from the design value, diffracted light other than the desired light, for example, second-order diffracted light, is generated. The second-order diffracted light generated at the metalens surface ML2 may become strong stray light and hinder the formation of a uniform illuminance distribution at the Fourier plane FR. In this case, the second-order diffracted light contains many components that are incident on the Fourier plane FR at a relatively large incident angle. In response to this, by using a light-transmitting member 260 whose transmittance decreases as the incident angle of light increases, it is possible to reduce stray light (second-order diffracted light) generated at the lighting metalens 223 (metalens surface ML2). As an embodiment of the light-transmitting member 260, for example, a bundle of hollow columnar protrusions (a lattice-like three-dimensional structure), a bundle of optical fibers, a thin film (single layer, multilayer), or a combination of these well-known techniques may be formed on the surface of a substrate (not shown) so as to obtain a desired incident angle characteristic.

[0048] As a method for designing and manufacturing the light-transmitting member 260, in addition to the conventional periodic structure, it is also possible to design a non-uniform film using the Needle method or a neural network. When the light-transmitting member 260 is formed using a thin film, the thin film material may be a combination of a high refractive index material such as Al2O3, TiO2, or ZrO2 and a low refractive index material such as MgF2 or SiO2.

[0049] FIG. 11 shows the transmittance characteristics versus the angle of incidence of the light-transmitting member 260. The horizontal axis of the graph shown in FIG. 11 indicates the angle of incidence θ of light to the light-transmitting member 260. The vertical axis of the graph shown in FIG. 11 indicates the transmittance corresponding to the angle of incidence θ. In the graph shown in FIG. 11, W indicates the incident angle width at which the transmittance changes. Note that "W=0 degrees" indicates that "the incident angle width W=0 degrees at which the transmittance changes." Also, C indicates the central value (central incident angle) of the incident angle width W at which the transmittance changes.

[0050] As can be seen from FIG. 11, when C=10 degrees, the transmittance is 1 in the range of 0≦θ≦10 degrees, and the transmittance is 0 in the range of θ>10 degrees. In other words, the light-transmitting member 260 may have a characteristic that the transmittance decreases from 1 to 0 when the incident angle θ of light to the light-transmitting member 260 exceeds 10 degrees. When C=20 degrees, the transmittance is 1 in the range of 0≦θ≦20 degrees, and the transmittance is 0 in the range of θ>20 degrees. In other words, the light-transmitting member 260 may have a characteristic that the transmittance decreases from 1 to 0 when the incident angle θ of light to the light-transmitting member 260 exceeds 20 degrees. When C=30 degrees, the transmittance is 1 in the range of 0≦θ≦30 degrees, and the transmittance is 0 in the range of θ>30 degrees. In other words, the light-transmitting member 260 may have a characteristic that the transmittance decreases from 1 to 0 when the incident angle θ of light to the light-transmitting member 260 exceeds 30 degrees.

[0051] Fig. 12 shows another example of the transmittance characteristics versus the angle of incidence of the light-transmitting member 260. The horizontal and vertical axes of the graph shown in Fig. 12 are the same as those of the graph shown in Fig. 11. In the graph shown in Fig. 12, "W=10 degrees" indicates that the "incident angle width W=10 degrees at which the transmittance changes."

[0052] As can be seen from FIG. 12, when C=10 degrees, the transmittance is 1 in the range of θ<5 degrees, and the transmittance is 0 in the range of 15 degrees<θ. Moreover, as the incident angle θ increases from 5 degrees to 15 degrees, the transmittance decreases linearly from 1 to 0. In other words, the translucent member 260 may have a characteristic that the transmittance decreases linearly from 1 to 0 when the incident angle θ of light to the translucent member 260 exceeds 5 degrees. When C=20 degrees, the transmittance is 1 in the range of θ<15 degrees, and the transmittance is 0 in the range of 25 degrees<θ. Moreover, as the incident angle θ increases from 15 degrees to 25 degrees, the transmittance decreases linearly from 1 to 0. In other words, the translucent member 260 may have a characteristic that the transmittance decreases linearly from 1 to 0 when the incident angle θ of light to the translucent member 260 exceeds 15 degrees. When C=30 degrees, the transmittance is 1 in the range of θ<25 degrees, and the transmittance is 0 in the range of 35 degrees<θ. Moreover, as the incident angle θ increases from 25 degrees to 35 degrees, the transmittance decreases linearly from 1 to 0. In other words, the light-transmitting member 260 may have a characteristic that the transmittance decreases linearly from 1 to 0 when the incident angle θ of light to the light-transmitting member 260 exceeds 25 degrees.

[0053] Next, an illumination device 300 according to a third embodiment will be described. Fig. 13 is a schematic diagram of the illumination device 300 according to the third embodiment. As shown in Fig. 13, the illumination device 300 according to the third embodiment includes a light source 310, an illumination optical system 320, an illumination relay lens 330, and a condenser lens 340, which are arranged in this order from the light source side. In Fig. 13, the filter cube 21 and the objective lens 11 included in the illumination device 300 are shown as the condenser lens 340, as in the first embodiment.

[0054] The light source 310 is configured similarly to the light source 210 according to the second embodiment. The light source 310 is disposed along the optical axis AX3 of the illumination optical system 320. The light source 310 may be disposed adjacent to a surface of the optical member 320 on the light source 310 side.

[0055] The illumination optical system 320 irradiates illumination light emitted from the light source 310 onto a predetermined illumination surface SR of the sample SA via an illumination relay lens 330 and a condenser lens 340 (filter cube 21 and objective lens 11). The illumination optical system 320 has an optical member 321 and a field stop FS3, which are arranged in order from the light source 310 side along the optical axis AX3.

[0056] Illumination light emitted from light source 310 is incident on optical member 321. Optical member 321 is configured in the same manner as optical member 121 according to the first embodiment. As also shown in FIG. 14, illumination metalens 323 is provided on the surface of optical member 321 opposite to light source 310. Illumination metalens 323 is configured by forming a first metalens surface ML3a having a predetermined structure on one surface (the surface opposite to light source 310) of a thin plate-like substrate (not shown), for example. Note that illumination metalens 323 may be bonded to the surface of optical member 321 opposite to light source 310, or may be formed integrally with optical member 321. First metalens surface ML3a has a metalens structure similar to metalens surface ML1 according to the first embodiment. In the third embodiment, illumination metalens 323 (first metalens surface ML3a) is designed so as to convert light from light source 310 incident on optical member 321 into substantially parallel light.

[0057] Field stop FS3 is disposed at the back focal position (the focal position on the opposite side to the light source 310 side) of illumination metalens 323. Corrective metalens 328 is provided at Fourier plane FR where field stop FS3 is disposed. Corrective metalens 328 is configured by forming a second metalens surface ML3b of a predetermined structure on one surface (the surface on the light source 310 side) of, for example, a thin plate-like substrate (not shown). Second metalens surface ML3b has a metalens structure similar to that of metalens surface ML1 according to the first embodiment. Corrective metalens 328 (second metalens surface ML3b) is designed so that chief ray PR incident on corrective metalens 328 (Fourier plane FR) from illumination metalens 323 is parallel to the optical axis AX3 of illumination optical system 320.

[0058] Note that light source 310 is disposed at a position conjugate with aperture stop AS3. Therefore, it can be said that illumination metalens 323 (first metalens surface ML3a) makes chief ray PR from light source 310 incident on optical member 321 approximately parallel to optical axis AX3 of illumination optical system 320. Here, "approximately parallel" means a state in which the angle with respect to optical axis AX3 is approximately 0 degrees to 5 degrees.

[0059] Illumination relay lens 330 (and condenser lens 340) are arranged side by side along the optical axis AX3 of illumination optical system 320. Illumination relay lens 330 collects the illumination light that has passed through field stop FS3 of illumination optical system 320 and corrective metalens 328 (second metalens surface ML3b), toward aperture stop AS3 that is arranged at the front focal position of condenser lens 340 (objective lens 11).

[0060] Illumination light emitted from light source 310 is incident on optical member 321 of illumination optical system 320. The illumination light incident on optical member 321 passes through optical member 321 and enters illumination metalens 323. The illumination light transmitted through illumination metalens 323 (first metalens surface ML3a) becomes substantially parallel light, passes through field stop FS2 and enters corrective metalens 328. The illumination light transmitted through corrective metalens 328 (second metalens surface ML3b) has a chief ray PR that becomes parallel to the optical axis AX3 of illumination optical system 320 and enters illumination relay lens 330. The light transmitted through illumination relay lens 330 passes through aperture stop AS3 and condenser lens 340 (filter cube 21 and objective lens 11) and is irradiated onto illumination surface SR.

[0061] In the third embodiment, an illumination metalens 323 is provided on the surface of optical member 321 opposite to the light source 310 side. Illumination metalens 323 converts light from light source 310 that is incident on optical member 321 into approximately parallel light, and causes the light to be incident on correction metalens 328 (Fourier plane FR). This allows the illumination light emitted from the light source 310 to be collimated and irradiated onto the illumination surface SR without, for example, arranging a reflecting member that collects light from the light source, or the above-mentioned fly-eye integrator and collector lens. This makes it possible to effectively utilize the light emitted from the light source 310, and also allows the illumination device 300 (and the microscope 1) to be made compact.

[0062] In the illumination device 300 according to the third embodiment, the above-mentioned conditional expression (1) may be satisfied, as in the first embodiment. By satisfying the conditional expression (1), the light emitted from the light source 310 can be effectively utilized, as in the first embodiment.

[0063] In the illumination device 300 according to the third embodiment, the above-mentioned conditional formula (1-1) may be satisfied, as in the first embodiment. By satisfying the conditional formula (1-1), the light emitted from the light source 310 can be effectively utilized, as in the case of the above-mentioned conditional formula (1).

[0064] Furthermore, the light source 310 may be a chip LED, and the optical surface of the optical member 321 facing the light source 310 may be a flat surface. This makes it possible to effectively utilize the light emitted from the light source 310, similar to the first embodiment.

[0065] The light source 310 does not have to be disposed adjacent to the surface of the optical member 321 on the light source 310 side. As described in the first embodiment, the light source 310 may be disposed at a distance (DA) from the surface of the optical member 321 on the light source 310 side.

[0066] In the lighting device 300 according to the third embodiment, the above-mentioned conditional formula (2) may be satisfied, as in the second embodiment. By designing the lighting metalens 323 (first metalens surface ML3a) so as to satisfy conditional formula (2), the illuminance distribution of the illumination light can be made uniform, as in the second embodiment.

[0067] In the lighting device 300 according to the third embodiment, it is desirable to provide a corrective metalens 328 that makes the chief ray PR incident on the Fourier plane FR from the lighting metalens 323 parallel to the optical axis AX3 of the lighting optical system 320.

[0068] In the third embodiment described above, a light-transmitting member similar to that of the second embodiment may be provided between illumination metalens 323 and field stop FS3 of illumination optical system 320. A light-transmitting member similar to that of the second embodiment may be provided between corrective metalens 328 and illumination relay lens 330. By using a light-transmitting member whose transmittance decreases as the angle of incidence of light increases, it is possible to reduce stray light (second-order diffracted light) generated in illumination metalens 323 (first metalens surface ML3a) or corrective metalens 328 (second metalens surface ML3b).

[0069] In the first and second embodiments described above, the illumination metalens 123, 223 may be a DOE lens that converts light from the light source 110, 210 that is incident on the optical member 121, 221 into approximately parallel light. In the third embodiment described above, the illumination metalens 323 may be a (first) DOE lens that converts light from the light source 310 that is incident on the optical member 321 into approximately parallel light. The corrective metalens 328 may be a (second) DOE lens that converts chief ray PR that is incident on the Fourier plane FR from the illumination metalens 323 into parallel light with respect to the optical axis AX3 of the illumination optical system 320, or may be an aspheric lens. EXAMPLES

[0070] Examples of the metalenses according to the first to third embodiments will be described below. The first example is an example of the lighting metalens 123 according to the first embodiment. The second example is an example of the second embodiment. Example 3 is an example of illumination metalens 223 according to an embodiment. Example 3 is an example of illumination metalens 323 and corrective metalens 328 according to a third embodiment.

[0071] Tables 1 to 3 are shown below, with Table 1 showing data on the various specifications for the first embodiment, Table 2 for the second embodiment, and Table 3 for the third embodiment. In the [Basic specifications] table, λ is the illumination wavelength (unit: nm), f is the focal length of the illumination optical system (unit: mm), and 2ω is the capture angle of the illumination light (unit: degrees). The [Metalens structure specifications] table shows the specifications of the columnar protrusions (pillars) when the metalens structure is a cylindrical structure.

[0072] In the [Surface Data] table, the surface number indicates the order of the optical surface from the light source side, R is the radius of curvature corresponding to each surface number (positive values ​​are used for optical surfaces convex toward the light source side), D is the thickness on the optical axis or air space corresponding to each surface number, and nIR is the refractive index for the illumination wavelength (λ=850nm) of the optical material corresponding to each surface number. The "∞" in the radius of curvature indicates a plane or an opening. In addition, the refractive index of air (n=1.000) is omitted. If the surface is spherical, an * is added to the surface number, and the paraxial radius of curvature is shown in the radius of curvature R column.

[0073] The phase function of the metalens structure is used in the design of metalens. In [Aspheric Data], the phase coefficient of the phase function of the metalens structure is shown. The phase coefficient "En" is expressed as "×10 -n For example, 1.234E-05=1.234×10 -5 When the height in the direction perpendicular to the optical axis is r and the n-th order coefficient (n=2, 4, 6, 8, 10, 12, 14, 16, 18, 20) is Cn, the phase function Φ(r) of the metalens structure is expressed by the following equation (A).

[0074] Φ(r)=Σ(Cn×r n ) (A)

[0075] In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally in "mm" unless otherwise specified, but this is not limited to this because the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced. Also, the wavelength of near-infrared light (λ = 850 nm) is used as the illumination wavelength, but this is not limited to this. It is also possible to use a wavelength of visible light or a wavelength of ultraviolet light, or a wavelength band that causes the sample SA to produce fluorescence.

[0076] The above explanation of the tables is common to all the embodiments, and therefore, duplicate explanations will be omitted below.

[0077] (First embodiment) The first example will be described with reference to FIG. 4 and Table 1. As shown in FIG. 4, the lighting metalens 123 according to the first example is provided on the surface of the optical member 121 opposite to the light source 110 side. The lighting metalens 123 is configured by forming a metalens surface ML1 of a predetermined structure on one surface (the surface opposite to the light source 110 side) of, for example, a thin plate-like substrate (not shown). The lighting metalens 123 is bonded to the surface of the optical member 121 opposite to the light source 110 side, but may be formed integrally with the optical member 121. The metalens surface ML1 has cylindrical protrusions (pillars) formed at a period smaller than the illumination wavelength, and the phase of the transmitted wavefront is realized by changing the width of the pillars.

[0078] The following Table 1 lists the specifications of the lighting metalens (and the optical member) according to the first example. The second surface is a bonding surface between the optical member and the lighting metalens. The fifth surface is a field stop surface.

[0079] (Table 1) [Basic specifications] λ=850 f=2.43 2ω=170 [Metalens structure specifications] Illumination wavelength λ: 850nm Metalens structure substrate: Quartz (nIR=1.453) Pillar shape: Cylinder Pillar material: amorphous silicon (nIR=3.5) Pillar period cp: 280nm Pillar height hp: 800nm Pillar width wp: 100-170nm [Face data] Surface number RD nIR (Light source surface) ∞ 0.00 1∞3.00 1.453 2∞0.53 1.453 3*∞0.00 4∞2.91 5∞ [Aspheric data] Surface 3 (metalens surface) C2=-0.206 C4=4.1452E-03 C6=-1.6680E-04 C8=8.3900E-06 C10=-4.7265E-07 C12=2.8529E-08 C14=-1.8040E-09 C16=1.1796E-10 C18=-7.9110E-12 C20=5.4117E-13

[0080] (Second Example) The second example will be described with reference to FIG. 8 and Table 2. As shown in FIG. 8, lighting metalens 223 according to the second example is provided on the surface of optical member 221 opposite to the light source 210 side. Lighting metalens 223 is configured by forming a metalens surface ML2 of a predetermined structure on one surface (the surface opposite to the light source 210 side) of, for example, a thin plate-like substrate (not shown). Note that lighting metalens 223 is bonded to the surface of optical member 221 opposite to the light source 210 side, but may be formed integrally with optical member 221. Metalens surface ML2 according to the second example has a metalens structure similar to that of metalens surface ML1 according to the first example.

[0081] The following Table 2 lists the specifications of the lighting metalens (and the optical member) according to the second example. The second surface is the bonding surface between the optical member and the lighting metalens. The fifth surface is the field stop surface (Fourier surface).

[0082] (Table 2) [Basic specifications] λ=850 f=2.91 2ω=170 [Metalens structure specifications] Illumination wavelength λ: 850nm Metalens structure substrate: Quartz (nIR=1.453) Pillar shape: Cylinder Pillar material: amorphous silicon (nIR=3.5) Pillar period cp: 280nm Pillar height hp: 800nm Pillar width wp: 100-170nm [Face data] Surface number RD nIR (Light source surface) ∞ 0.00 1∞3.00 1.453 2∞0.53 1.453 3*∞0.00 4∞2.91 5∞ [Aspheric data] Surface 3 (metalens surface) C2=-0.1720 C4=3.0846E-04 C6=-6.2736E-05 C8=6.4045E-06 C10=-3.6570E-07 C12=1.5397E-08 C14=-6.4899E-10 C16=1.7813E-11

[0083] (Third Example) The third example will be described with reference to FIG. 14 and Table 3. As shown in FIG. 14, lighting metalens 323 according to the third example is provided on the surface of optical member 321 opposite to the light source 310 side. Lighting metalens 323 is configured by forming a first metalens surface ML3a of a predetermined structure on one surface (the surface opposite to the light source 310 side) of, for example, a thin plate-like substrate (not shown). Note that lighting metalens 323 is bonded to the surface of optical member 221 opposite to the light source 210 side, but may be formed integrally with optical member 221. First metalens surface ML3a has a metalens structure similar to that of metalens surface ML1 according to the first example.

[0084] Corrective metalens 328 is provided at the Fourier plane FR where field stop FS3 is located. Corrective metalens 328 is formed by forming a second metalens surface ML3b of a predetermined structure on one surface (the surface on the light source 310 side) of, for example, a thin plate-like substrate (not shown). Second metalens surface ML3b has the same metalens structure as metalens surface ML1 of the first example.

[0085] Table 3 below lists the specifications of the lighting metalens and corrective metalens (and optical member) according to the third example. Note that the second surface is the bonding surface between the optical member and the lighting metalens. The fifth surface is the field stop surface (Fourier surface).

[0086] (Table 3) [Basic specifications] λ=850 f=2.91 2ω=170 [Metalens structure specifications] Illumination wavelength λ: 850nm Metalens structure substrate: Quartz (nIR=1.453) Pillar shape: Cylinder Pillar material: amorphous silicon (nIR=3.5) Pillar period cp: 280nm Pillar height hp: 800nm Pillar width wp: 100-170nm [Face data] Surface number RD nIR (Light source surface) ∞ 0.00 1∞3.00 1.453 2∞0.53 1.453 3*∞0.00 4∞2.91 5*∞ 0.53 1.453 [Aspheric data] Surface 3 (first metalens surface) C2=-0.1720 C4=3.0846E-04 C6=-6.2736E-05 C8=6.4045E-06 C10=-3.6570E-07 C12=1.5397E-08 C14=-6.4899E-10 C16=1.7813E-11 Surface No. 5 (Second metalens surface) C2=-2.8424E-02 C4=1.8582E-03 C6=5.9995E-05 C8=3.3289E-06

[0087] Next, a table of [Values ​​Corresponding to Conditional Expressions] is shown below. This table shows the values ​​corresponding to each of the conditional expressions (1) and (2) for all the examples (Examples 1 to 3). Condition (1) 0≦DA / DB≦0.1 Conditional formula (2) h=fm×sinθ

[0088] [Conditional Expression Corresponding Values] (First to Third Examples) Conditional Expression 1st Example 2nd Example 3rd Example (1) 0.00 0.00 0.00 (2) ― 2.90 2.90 (θ=85 degrees) (θ=85 degrees) (fm=2.91) (fm=2.91)

[0089] According to each of the above embodiments, it is possible to realize an illumination device capable of effectively utilizing the light emitted from the light source.

[0090] Here, the above examples show specific examples of each embodiment, and each embodiment is not limited to these. [Explanation of symbols]

[0091] 1. Microscope 100 Illumination device (first embodiment) 110 Light source 120 Illumination optical system 121 Optical components 123 Metalens for lighting (ML1 Metalens surface) 200 Illumination device (second embodiment) 200A Lighting Device (Modified Version) 210 Light source 220 Illumination optical system 221 Optical components 223 Metalens for lighting (ML2 Metalens surface) 260 Translucent material 300 Illumination device (third embodiment) 310 light source 320 Illumination optical system 321 Optical components 323 Metalens for lighting (ML3a 1st metalens surface) 328 Corrective metalens (ML3b second metalens surface)

Claims

1. A light source; an illumination optical system that illuminates with light from the light source, the light source is disposed along an optical axis of the illumination optical system; the illumination optical system has an optical member on which light from the light source is incident, an illumination metalens that converts light from the light source that is incident on the optical member into substantially parallel light is provided on a surface of the optical member opposite to the light source side; A lighting device that satisfies the following conditional expressions: 0≦DA / DB≦0.1 where DA is the distance on the optical axis from the light source to the surface of the optical member facing the light source. DB: the distance on the optical axis from the light source to the surface of the optical member opposite to the light source side

2. The light distribution of the light source is a Lambertian distribution, 2. The lighting device according to claim 1, which satisfies the following conditional expression: h = fm × sin θ where h is the image height on a Fourier plane that passes through the rear focus of the illumination metalens and is perpendicular to the optical axis of the illumination optical system. θ: divergence angle of the light source fm: focal length of the lighting metalens

3. 3. The lighting device according to claim 2, wherein a corrective metalens is provided at the Fourier plane in the illumination optical system to make chief rays incident on the Fourier plane from the illumination metalens parallel to an optical axis of the illumination optical system.

4. the illumination optical system has a light-transmitting member capable of transmitting light emitted from the illumination metalens, 4. The lighting device according to claim 1, wherein the transmittance of the light-transmitting member decreases as the angle of incidence of light to the light-transmitting member increases.

5. the light source is disposed adjacent to a surface of the optical member on the light source side, 5. The lighting device according to claim 1, which satisfies the following conditional expression: DA / DB=0

6. An illumination device according to any one of claims 1 to 5 for illuminating a sample; and an observation optical system for receiving light from the sample.

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