Light irradiation device and sample observation device

Abstract

A light irradiation device 2 is provided with: a light source 21 that outputs light L0 having coherency; a condensing element 23 that has a condensing axis F1 and a noncondensing axis F2 crossing the condensing axis F1, and condenses the light L0 on a condensing line K to generate planar light L1; and an aperture mask 22 having an opening part 24 that restricts part of a light flux of the light L0 traveling from the light source 21 to the condensing element 23. The opening part 24 of the aperture mask 22 has an opening edge 25A disposed so as to extend in a direction along the condensing axis F1 of the condensing element 23, and when the opening edge 25A is projected onto the condensing line K, a corresponding projected portion P has a linear spread.

Description

[Technical field]

[0001] The present disclosure relates to a light irradiation device and a sample observation device. [Background technology]

[0002] SPIM (Selective Plane Illumination Microscopy) is known as one of the techniques for observing the inside of a sample having a three-dimensional structure such as a cell. For example, a sample observation device described in Patent Document 1 is a technique related to this technique. The sample observation device in Patent Document 1 is configured with an illumination optical system that illuminates a sample with planar light, a scanning unit that scans the sample with respect to the illumination surface of the planar light, and an imaging optical system that has an observation axis inclined with respect to the illumination surface and that images the observation light generated in the sample by the illumination of the planar light. Then, a plurality of partial image data corresponding to parts of the light image formed by the observation light by the imaging optical system are obtained, and observation image data of the sample is generated based on these partial image data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-063292 A Summary of the Invention [Problem to be solved by the invention]

[0004] The planar light used in the above-mentioned sample observation device is formed by, for example, converging light emitted from a light source with a converging element such as a cylindrical lens. When irradiating the sample with the planar light, it is preferable to place an aperture mask on the light path to limit the irradiation range of the planar light so that the planar light is not irradiated onto adjacent observation areas on the sample. However, since coherent light such as laser light is a coherent light, interference fringes are generated due to diffraction at the edge of the aperture mask, and the irradiance distribution of the planar light may become non-uniform.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a light irradiation device and a sample observation device capable of outputting planar light having a uniform irradiance distribution. [Means for solving the problem]

[0006] A light irradiation device according to one aspect of the present disclosure includes a light source that outputs coherent light, a focusing element having a focusing axis and a non-focusing axis intersecting the focusing axis and focusing the light onto a focusing line to generate planar light, and an aperture mask having an opening that limits a portion of the light flux traveling from the light source to the focusing element, wherein the opening of the aperture mask has an opening edge arranged to extend in a direction along the focusing axis of the focusing element, and when the opening edge is projected onto the focusing line, the projected portion has a linear extension.

[0007] In this light irradiation device, when the opening edge of the aperture mask, which is arranged to extend in a direction along the focusing axis of the focusing element, is projected onto the focusing line, the projected portion has a linear spread. In an aperture mask in which the projected portion becomes a point when the opening edge is projected onto the focusing line, interference fringes caused by diffraction at the opening edge tend to intensify, resulting in a non-uniform irradiance distribution of the planar light. In contrast, in an aperture mask in which the projected portion has a linear spread, interference fringes caused by diffraction at the opening edge do not intensify, and the irradiance distribution of the planar light can be made uniform. Therefore, this light irradiation device can output planar light having a uniform irradiance distribution.

[0008] The opening may have an asymmetric shape with respect to the focusing line. The opening edge may have a shape that is convex toward the outside of the focusing line. The opening may have a hexagonal shape. With these configurations, interference fringes caused by diffraction at the opening edge are further suppressed, and the irradiance distribution of the planar light is further uniformed.

[0009] The opening may be trapezoidal. The opening edge may be zigzag. The opening edge may have a shape that is convex toward the outside of the focusing line. In these configurations, interference fringes caused by diffraction at the opening edge are further suppressed, and the irradiance distribution of the planar light is further uniformed.

[0010] The opening may be rectangular, and the opening edge may intersect with the light collection axis at a predetermined angle. Even in this configuration, interference fringes caused by diffraction at the opening edge are further suppressed, and the irradiance distribution of the planar light is further uniformed.

[0011] The light source may be a light source that outputs laser light. Laser light has a large irradiance, but is a light with strong coherence, and is prone to interference fringes due to diffraction at the edge of the aperture mask. Therefore, by applying the aperture mask having the above configuration to the laser light, it is possible to suitably output planar light having a uniform irradiance distribution.

[0012] A sample observation device according to one aspect of the present disclosure includes the above-mentioned light irradiation device and a detection unit that detects observation light generated in the sample by irradiation with planar light from the light irradiation device.

[0013] In this sample observation device, the interference fringes caused by diffraction at the opening edges of the aperture mask do not intensify, and the irradiance distribution of the planar light can be made uniform. Therefore, in this sample observation device, the sample can be observed with high accuracy by irradiating the sample with planar light with a uniform irradiance distribution. Effect of the Invention

[0014] According to the present disclosure, it is possible to output planar light having a uniform irradiance distribution. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram showing an embodiment of a sample observation device. [Diagram 2]FIG. 2 is a schematic diagram showing an example of the configuration of a light irradiation device. [Diagram 3] FIG. 2A is a diagram showing the shape of an opening of an aperture mask according to a comparative example, and FIG. 2B is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 4] FIG. 2A is a diagram showing the shape of an opening of an aperture mask according to an embodiment, and FIG. 2B is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Diagram 5] 10(a) is a diagram showing the shape of an opening of an aperture mask according to another embodiment, and (b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. FIG. [Figure 6] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 7] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 8] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 9] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 10] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. [Figure 11] FIG. 13(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment, and FIG. 13(b) is a graph showing the irradiance distribution of planar light when the aperture mask is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, preferred embodiments of a light irradiation device and a sample observation device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0017] FIG. 1 is a schematic diagram showing an embodiment of a sample observation device. This sample observation device 1 is a device that irradiates a sample S with planar light L1, and forms an image of light (e.g., fluorescence, scattered light, etc.) generated inside the sample S by the irradiation of the planar light L1 on an imaging plane to obtain observation image data of the inside of the sample S. Examples of this type of sample observation device 1 include a slide scanner that obtains and displays an image of the sample S held on a slide glass, or a plate reader that obtains image data of the sample S held on a microplate and analyzes the image data. Examples of the sample S to be observed include human or animal cells, tissues, organs, animals or plants themselves, plant cells, tissues, etc. Also, the sample S may be contained in a solution, a gel, or a substance with a different refractive index from that of the sample S.

[0018] As shown in FIG. 1, the sample observation device 1 includes a light irradiation device 2, a scanning unit 4, an imaging optical system 5, an image acquisition unit (detection unit) 6, and a computer 7. The light irradiation device 2 is a device that outputs planar light L1 to be irradiated onto the sample S. The planar light L1 is light obtained by shaping laser light or low-coherent light into a planar shape. The planar light L1 output from the light irradiation device 2 travels along an optical axis P1 and is irradiated onto the sample S. In the sample S irradiated with the planar light L1, observation light L2 is generated at the irradiation surface R of the planar light L1. The observation light L2 is, for example, fluorescence excited by the planar light L1, scattered light of the planar light L1, or diffuse reflected light of the planar light L1.

[0019] The scanning unit 4 is a mechanism for scanning the sample S across the irradiation surface R of the planar light L1. In this embodiment, the scanning unit 4 is configured with a moving stage 12 for moving a sample container 11 that holds the sample S. The sample container 11 is, for example, a microplate, a slide glass, a petri dish, etc. In this embodiment, a microplate is exemplified. In the sample container 11, a plurality of wells 13 in which the samples S are placed are arranged, for example, in a straight line (or in a matrix). The sample container 11 may be fixed to the moving stage 12. The bottom surface of the well 13 is an input surface of the planar light L1 for the sample S placed in the well 13. The sample container 11 is arranged with respect to the moving stage 12 so that this input surface is perpendicular to the optical axis P1 of the planar light L1.

[0020] As shown in Fig. 1, the moving stage 12 scans the sample container 11 in a preset direction according to a control signal from the computer 7. In this embodiment, the moving stage 12 scans the sample container 11 in one direction in a plane perpendicular to the optical axis P1 of the planar light L1. Here, the direction of the optical axis P1 of the planar light L1 is called the Z axis, the scanning direction of the sample container 11 by the moving stage 12 is called the Y axis, and the direction perpendicular to the Y axis in the plane perpendicular to the optical axis P1 of the planar light L1 is called the X axis. The irradiation surface R of the sample S with the planar light L1 is a surface in the XZ plane.

[0021] The imaging optical system 5 is an optical system that forms an image of the observation light L2 generated on the sample S by irradiation with the planar light L1. The imaging optical system 5 includes, for example, an objective lens and an imaging lens. The optical axis of the imaging optical system 5 is the observation axis P2 of the observation light L2. In the example of FIG. 1, the observation axis P2 of the imaging optical system 5 is inclined at a predetermined angle with respect to the irradiation surface R of the sample S that is irradiated with the planar light L1. The inclination angle of the observation axis P2 is also in agreement with the angle formed between the optical axis P1 of the planar light L1 toward the sample S and the observation axis P2.

[0022] The image acquisition unit 6 is a part that detects the observation light L2 formed by the imaging optical system 5. The image acquisition unit 6 includes, for example, an imaging device that captures an optical image by the observation light L2. Examples of the imaging device include area image sensors such as a CMOS image sensor and a CCD image sensor. These area image sensors are disposed on the imaging plane formed by the imaging optical system 5, capture an optical image by, for example, a global shutter or a rolling shutter, and output two-dimensional image data to a computer 7.

[0023] The computer 7 is physically configured to include memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, a storage unit such as a hard disk, and a display unit such as a display. Examples of the computer 7 include a personal computer, a cloud server, and a smart device (a smartphone, a tablet terminal, etc.). The computer 7 functions as a controller for controlling the operation of the light irradiation device 2 and the moving stage 12, an image generation unit for generating observation image data of the sample S, an analysis unit for analyzing the observation image data, etc., by executing a program stored in the memory on the CPU of the computer system.

[0024] Next, the above-mentioned light irradiation device 2 will be described in more detail.

[0025] FIG. 2 is a schematic diagram showing an example of the configuration of a light irradiation device. As shown in the figure, the light irradiation device 2 includes a light source 21 that outputs light L0, an aperture mask 22 that limits a part of the light flux of the light L0, and a focusing element 23 that focuses the light L0 to generate planar light L1, as will be described in detail later. The light source 21 may be a laser light source such as a laser diode or a solid-state laser light source. The light source 21 is not limited to a light source that outputs laser light, and may be a light source that outputs low coherent light such as an SLD (Super luminescent diode). Both laser light and low coherent light are light having coherence. The aperture mask 22A has an opening 24 that limits a part of the light flux of the light L0 from the light source 21 toward the focusing element 23. By limiting a part of the light flux of the light L0 by the opening 24, it is possible to limit the irradiation range of the planar light L1 output from the light irradiation device 2 so that the planar light is not irradiated to adjacent observation areas in the sample S placed in the sample container 11 of the sample observation device 1.

[0026] The light-collecting element 23 is, for example, a cylindrical lens, an axicon lens, a free-form lens, or a spatial light modulator, and is optically coupled to the light source 21. The light-collecting element 23 has a light-collecting axis F1 and a non-light-collecting axis F2 intersecting (here, perpendicular to) the light-collecting axis F1, and collects the light L0 that has passed through the opening 24 onto a light-collecting line K to generate planar light L1. In the example of FIG. 2, the light-collecting element 23 is a cylindrical lens. FIG. 2(a) shows the optical axis of the light L0 in the light-collecting axis side cross section (YZ cross section) of the light-collecting element 23, and FIG. 2(b) shows the optical axis of the light L0 in the non-light-collecting axis side cross section (XZ cross section) of the light-collecting element 23.

[0027] As shown in Fig. 2(a), when viewed from the collection axis side cross section (YZ cross section), light L0 that has passed through the opening 24 passes through the collecting element 23 and is collected along the collection axis F1 of the collecting element 23. On the other hand, as shown in Fig. 2(b), when viewed from the non-collection axis side cross section (XZ cross section), light L0 that has passed through the opening 24 is not collected by the collecting element 23 and maintains the state before entering the collecting element 23. Therefore, light L0 passes through the collecting element 23 and is collected only along one axis (Y axis) of the collection axis F1, becoming planar light L1 having a certain width in the X-axis direction.

[0028] Here, as described above, when an aperture mask is disposed on the optical path of coherent light such as laser light, since coherent light is generally light having strong coherence, there is a problem that interference fringes are generated in the laser light after passing through the opening due to diffraction at the opening edge of the aperture mask. This problem can occur even if the light passing through the opening of the aperture mask is low coherent light. The interference fringes caused by diffraction at the opening edge of the aperture mask overlap and intensify when the light is focused by the focusing element in the direction along the focusing axis, so that it is considered that the irradiance distribution of the planar light obtained by focusing the light becomes non-uniform.

[0029] 3(a) is a diagram showing the shape of an opening of an aperture mask according to a comparative example. The aperture mask 122 according to this comparative example has a rectangular (quadrilateral) opening 124 including an opening edge 125A corresponding to the long side and an opening edge 125B corresponding to the short side. The aperture mask 122 is disposed on the optical path of the light L0 such that, when viewed from the optical axis direction of the light L0, the opening edge 125A extends in a direction parallel to the optical axis F1 of the focusing element 23 and the opening edge 125B extends in a direction perpendicular to the optical axis of the focusing element 23. When viewed from the optical axis direction of the light L0, the focusing line K of the light L0 by the focusing element 23 is located on a line connecting the centers of the left and right opening edges 125A, 125A.

[0030] 3(a), when the aperture edge 125A is projected onto the condensing line, the projection portion P of the aperture edge 125A on the condensing line K is dot-shaped. Therefore, in the aperture mask 122, when the light L0 that has passed through the opening 124 is condensed by the condensing element 23, interference fringes caused by diffraction at the aperture edge 125A overlap and intensify at one point on the condensing line K.

[0031] 3(b) is a graph showing the irradiance distribution of planar light when an aperture mask according to a comparative example is used. In this figure, the horizontal axis indicates coordinate values ​​on the focusing line (X-axis), and the vertical axis indicates the irradiance of the planar light. As shown in this figure, in the planar light L1 when an aperture mask according to a comparative example is used, the amplitude of the irradiance distribution near both ends in the X-axis direction is 5 W / mm 2 The amplitude of the irradiance distribution becomes smaller toward the center in the X-axis direction, but the amplitude of the irradiance distribution near the center is also 1 W / mm 2 The amplitude of the irradiance distribution refers to the width between the maximum and minimum values ​​in a region where the irradiance is approximately uniform.

[0032] On the other hand, FIG. 4(a) is a diagram showing the shape of the opening of the aperture mask according to the embodiment. This aperture mask 22A has a rectangular (square) opening 24A having an opening edge 25A corresponding to the long side and an opening edge 25B corresponding to the short side, as in the comparative example. In the aperture mask 22A, the shape of the opening 24A itself is the same as that of the opening 124 in the comparative example, but unlike the comparative example, the rectangular opening 24A is rotated at a predetermined angle around the optical axis of the light L0. As a result, in this aperture mask 22A, when viewed from the optical axis direction of the light L0, the opening edge 25A intersects at a predetermined angle with respect to the direction parallel to the focusing axis F1, and the opening edge 25B intersects at a predetermined angle with respect to the direction parallel to the non-focusing axis.

[0033] The predetermined angle is, for example, 1° or more and 5° or less. By setting the predetermined angle to 1° or more, it is possible to fully exert the effect of reducing interference fringes. Furthermore, by setting the predetermined angle to 5° or less, it is possible to prevent the tail of the irradiance distribution from spreading excessively, and it is possible to sufficiently ensure a region where the irradiance is flat. Note that, when setting the optimum predetermined angle, the length of the opening 24A in the direction of the collection axis F1 may also be taken into consideration.

[0034] 4(a), when the aperture edge 25A of the aperture mask 22A according to this embodiment is projected onto the condensing line, the projection portion P of the aperture edge 25A on the condensing line K has a linear spread. Therefore, in the aperture mask 22A, when the light L0 that has passed through the opening 24A is condensed by the condensing element 23, it is possible to suppress interference fringes caused by diffraction at the aperture edge 25A from overlapping and intensifying on the condensing line K.

[0035] Fig. 4(b) is a graph showing the irradiance distribution of planar light when the aperture mask according to the embodiment is used. In this figure, as in Fig. 3(b), the horizontal axis indicates coordinate values ​​on the focusing line (X-axis), and the vertical axis indicates the irradiance of the planar light. As shown in this figure, in the planar light L1 when the aperture mask according to the embodiment is used, the amplitude of the irradiance distribution near both ends in the X-axis direction is 1 W / mm 2 The amplitude of the irradiance distribution near the center is almost 0 W / mm 2 is kept to a minimum.

[0036] As described above, in the light irradiation device 2, when the opening edge 25A arranged to extend in the direction along the light collection axis F1 of the light collection element 23 is projected onto the light collection line K at the opening 24A of the aperture mask 22A, the projection part P has a linear spread. In the aperture mask 22 of the comparative example in which the projection part P becomes a point when the opening edge 25A is projected onto the light collection line K, the interference fringes caused by the diffraction at the opening edge 25A tend to intensify, and the irradiance distribution of the planar light L1 tends to be non-uniform. In contrast, in the aperture mask 22A of the embodiment in which the projection part P has a linear spread, the interference fringes caused by the diffraction at the opening edge 25A do not intensify, and the irradiance distribution of the planar light L1 can be made uniform. Therefore, in this light irradiation device 2, the planar light L1 having a uniform irradiance distribution can be output.

[0037] As a technique for suppressing interference fringes caused by the diffraction of light at the opening edge of an aperture mask, for example, there is a method of placing an optical filter called an apodization filter or a soft aperture on the optical path. There is also a method of suppressing the diffraction component by placing an aspheric lens on the optical path instead of an optical filter. However, in these methods, it is necessary to optimize the optical element according to the wavelength and beam diameter of the laser light used, and if a laser light that does not match the characteristics of the optical element is used, there is a risk that the effect of suppressing interference fringes caused by the diffraction of light at the opening edge will not be fully exerted.

[0038] In contrast, in the light irradiation device 2, the configuration of the opening edge 25A of the aperture mask 22A suppresses interference fringes caused by the diffraction of the light L0 at the opening edge 25A. This method does not require optimizing the optical elements according to the wavelength or beam diameter of the light L0 used, and is effective for various types of light L0. This is particularly significant when applied to an apparatus that is intended to irradiate the sample S with light L0 having different wavelengths and beam diameters as planar light L1 coaxially, such as the sample observation device 1 shown in the above embodiment.

[0039] Fig. 5(a) is a diagram showing the shape of the opening of an aperture mask according to another embodiment. In the aperture mask 22B shown in the figure, instead of the rectangular opening 24A rotated at a predetermined angle around the optical axis of the light L0 (see Fig. 4(a)), the opening 24B has a parallelogram shape (square shape). As a result, in this aperture mask 22B, when viewed from the optical axis direction of the light L0, the opening edge 25A is inclined at a predetermined angle with respect to a direction parallel to the focusing axis F1, and the opening edge 25B is parallel to the non-focusing axis.

[0040] In the case of such an aperture mask 22B, when the opening edge 25A is projected onto the condensing line, the projection portion P of the opening edge 25A on the condensing line K has a linear spread as shown in Fig. 5(a). Therefore, in the aperture mask 22B, when the light L0 passing through the opening 24B is condensed by the condensing element 23, the interference fringes caused by the diffraction at the opening edge 25A can be prevented from overlapping and strengthening on the condensing line K. As shown in Fig. 5(b), the irradiance distribution of the planar light L1 when the aperture mask 22B is used is almost the same as that when the aperture mask 22A is used.

[0041] FIG. 6(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment. In the aperture mask 22C shown in the figure, the opening 24C has an asymmetric shape with respect to the condensing line K. More specifically, in the example of FIG. 6(a), the shape of the opening 24C is an isosceles trapezoid (rectangle). As a result, in this aperture mask 22C, when viewed from the optical axis direction of the light L0, the opening edge 25A is inclined at a predetermined angle with respect to the direction parallel to the condensing axis F1, and the opening edge 25B is parallel to the non-condensing axis. In the figure, the length of the lower base of the opening 24C in the non-condensing axis F2 direction is longer than the length of the upper base in the non-condensing axis F2 direction, but this length relationship may be reversed.

[0042] In the case of such an aperture mask 22C, when the opening edge 25A is projected onto the condensing line, the projection portion P of the opening edge 25A on the condensing line K has a linear spread as shown in Fig. 6(a). Therefore, in the aperture mask 22C, when the light L0 passing through the opening 24C is condensed by the condensing element 23, the interference fringes caused by the diffraction at the opening edge 25A can be prevented from overlapping and strengthening on the condensing line K. As shown in Fig. 6(b), the irradiance distribution of the planar light L1 when the aperture mask 22C is used is almost the same as that when the aperture mask 22A is used.

[0043] 7(a) is a diagram showing the shape of the opening of an aperture mask according to yet another embodiment. In the aperture mask 22D shown in the figure, the shape of the opening 24D is an isosceles trapezoid, as in the aperture mask 22C, and the opening edge 25A is zigzag. In the aperture mask 22D, when the opening edge 25A is projected onto the condensing line, the projection portion P of the opening edge 25A on the condensing line K has a linear spread. Therefore, in the aperture mask 22D, when the light L0 passing through the opening 24D is condensed by the condensing element 23, the interference fringes caused by the diffraction at the opening edge 25A can be suppressed from overlapping and strengthening on the condensing line K.

[0044] As shown in Fig. 7(b), the irradiance distribution of the planar light L1 when the aperture mask 22D is used is almost the same as that when the aperture mask 22A is used. Comparing the results of Fig. 7(b) and Fig. 4(b), the results of Fig. 7(b) show that the rising portion of the irradiance distribution near both ends in the X-axis direction of the planar light L1 is steeper, and the amplitude of the irradiance distribution near both ends in the X-axis direction is also slightly smaller. In the example of Fig. 7(a), the unevenness of the zigzag opening edge 25A is sharp, but the unevenness of the opening edge 25A may be curved, such as in an arc shape or a sinusoidal wave shape.

[0045] 8(a), rectangular (square) opening 24E may be rotated by a predetermined angle around the optical axis of light L0, and opening edge 25A may be zigzag. Even when such an aperture mask 22E is used, it is possible to obtain a planar irradiance distribution of light L1 that is substantially the same as that when aperture mask 22D is used, as shown in FIG. 8(b).

[0046] FIG. 9(a) is a diagram showing the shape of an opening of an aperture mask according to yet another embodiment. In the aperture mask 22F shown in the figure, the opening edge 25A of the opening 24F has a shape that is convex toward the outside of the light collection line K. More specifically, in the example of FIG. 9(a), the opening 24F has a hexagonal shape, and two opposing sides are arranged along a direction parallel to the non-light collection axis F2. The opening 24F is not a regular hexagon, and the corners of the hexagon are positioned on one side of the light collection line K (here, the lower side of the paper) at the opening edge 25A. Therefore, this opening 24F has an asymmetric shape with respect to the light collection line K, similar to the opening 24C of the aperture mask 22C. The corners of the hexagon may be positioned on the other side of the light collection line K (the upper side of the paper).

[0047] In such an aperture mask 22F, when the opening edge 25A is projected onto the condensing line, the projection portion P of the opening edge 25A on the condensing line K has a linear spread. Therefore, in the aperture mask 22F, when the light L0 passing through the opening 24F is condensed by the condensing element 23, it is possible to suppress the interference fringes caused by the diffraction at the opening edge 25A from overlapping and strengthening on the condensing line K. As shown in Fig. 9(b), the irradiance distribution of the planar light L1 when the aperture mask 22C is used is almost the same as that when the aperture mask 22A is used, but the amplitude of the irradiance distribution near both ends in the X-axis direction is further suppressed.

[0048] An example of a shape in which the opening edge 25A has a convex shape toward the outside of the focusing line K is an aperture mask 22G shown in Fig. 10(a) in which the opening edge 25A of the rectangular opening 24G is gently curved so as to be convex toward the outside. In this case, as shown in Fig. 10(b), the irradiance distribution of the planar light L1 has slight amplitude at the rising portions of the irradiance distribution near both ends in the X-axis direction, but the overall result is almost the same as when the aperture mask 22A is used.

[0049] As another example of the shape of the opening edge 25A that is convex toward the outside of the collection line K, for example, as in aperture mask 22H shown in Fig. 11(a), a rectangular opening 24H may be rotated by a predetermined angle around the optical axis of light L0, and opening edge 25A may be gently curved to be convex toward the outside. In this case as well, as shown in Fig. 11(b), slight amplitude occurs in the rising portions of the irradiance distribution of the planar light L1 near both ends in the X-axis direction, but the overall result is almost the same as when aperture mask 22A is used. [Explanation of symbols]

[0050] 1...sample observation device, 6...image acquisition unit (detection unit), 21...light source, 22 (22A to 22H)...aperture mask, 23...light-collecting element, 24 (24A to 24H)...opening, 25A...opening edge, F1...light-collecting axis, F2...non-light-collecting axis, K...light-collecting line, L0...light, L1...area light, P...projection portion, S...sample.

Claims

1. A light source that outputs coherent light; a focusing element having a focusing axis and a non-focusing axis intersecting the focusing axis, focusing the light on a focusing line to generate planar light; an aperture mask having an opening for limiting a portion of the light beam from the light source toward the light collecting element; the opening of the aperture mask has an opening edge arranged to extend in a direction along the focusing axis of the focusing element, The opening edge, when viewed from the optical axis direction of the light, intersects the focusing line non-orthogonally and in a straight line, and when the opening edge is projected onto the focusing line, the projected portion has a linear expansion.

2. The light irradiation device according to claim 1 , wherein the opening has an asymmetric shape with respect to the light collecting line.

3. 3. The light irradiation device according to claim 1, wherein the opening edge has a shape that is convex toward an outside of the light collecting line.

4. 4. The light irradiation device according to claim 1, wherein the opening is hexagonal in shape.

5. 3. The light irradiation device according to claim 1, wherein the opening is trapezoidal.

6. The opening is rectangular in shape, The light irradiation device according to claim 1 , wherein the opening edge intersects with the light collecting axis at a predetermined angle.

7. 5. The light irradiation device according to claim 1, wherein the opening edge has a shape that forms a single convexity toward an outside of the light collecting line.

8. 2. The light irradiation device according to claim 1, wherein the opening is hexagonal and asymmetrical about the light collecting line.

9. A light source that outputs coherent light; a focusing element having a focusing axis and a non-focusing axis intersecting the focusing axis, focusing the light on a focusing line to generate planar light; a stand-alone aperture mask having an opening for limiting a portion of the light flux from the light source toward the light collecting element; the opening of the aperture mask has an opening edge arranged to extend in a direction along the light collection axis of the light collection element, and when the opening edge is projected onto the light collection line, the projected portion has a linear expansion; The opening of the light irradiation device is trapezoidal.

10. A light source that outputs coherent light; a focusing element having a focusing axis and a non-focusing axis intersecting the focusing axis, focusing the light on a focusing line to generate planar light; a stand-alone aperture mask having an opening for limiting a portion of the light flux from the light source toward the light collecting element; the opening of the aperture mask has an opening edge arranged to extend in a direction along the light collection axis of the light collection element, and when the opening edge is projected onto the light collection line, the projected portion has a linear expansion; The opening is rectangular in shape, The opening edge intersects with the light collecting axis at a predetermined angle.

11. A light source that outputs coherent light; a focusing element having a focusing axis and a non-focusing axis intersecting the focusing axis, focusing the light on a focusing line to generate planar light; a stand-alone aperture mask having an opening for limiting a portion of the light flux from the light source toward the light collecting element; the opening of the aperture mask has an opening edge arranged to extend in a direction along the light collection axis of the light collection element, and when the opening edge is projected onto the light collection line, the projected portion has a linear expansion; The opening is hexagonal and asymmetric with respect to the light collection line.

12. The light irradiation device according to any one of claims 1 to 11, wherein the opening has an opening edge arranged to extend in a direction along the non-focusing axis of the focusing element, and the opening edge is parallel to the focusing line when viewed from the optical axis direction of the light.

13. The light irradiation device according to any one of claims 1 to 11, wherein the opening has an opening edge arranged to extend in a direction along the non-focusing axis of the focusing element, and the opening edge is non-parallel to the focusing line when viewed from the optical axis direction of the light.

14. 14. The light irradiation device according to claim 1, wherein the light source is a light source that outputs a laser beam as the light.

15. A light irradiation device according to any one of claims 1 to 14, a detection unit that detects observation light generated in a sample by the irradiation of the planar light from the light irradiation device.

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