Illumination optics and illumination device

Abstract

To suppress unevenness of illumination caused by light distribution characteristics of a light source at a wide observation magnification from low to high.SOLUTION: An illumination optical system 10 includes an illumination optical element 5 and a correction lens 6. The illumination optical element 5 has an optical surface 5a directed to an illumination surface SP and irradiates the illumination surface SP with light in a planar manner. The optical surface 5a has a plurality of refractive surfaces RS that are formed at regular pitches in an orthogonal direction orthogonal to an optical axis AX and refracts light toward a region R1, and a center plane CS that intersects the optical axis AX provided at a position closer to the optical axis AX than the plurality of refractive surfaces RS. The correction lens 6 is provided between the illumination optical element 5 and the illumination surface SP, and corrects telecentricity of light passing through the center plane CS.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosure of this specification relates to an illumination optical system and an illumination device.

Background Art

[0002] In the fields of microscopes and semiconductor exposure apparatuses, Kohler illumination is generally adopted in order to illuminate a specimen surface uniformly. However, in Kohler illumination, unevenness of illumination due to the light distribution characteristics of a light source may occur. With respect to such technical problems, a technique for suppressing unevenness of illumination due to the light distribution characteristics in Kohler illumination by using a fly-eye lens has been proposed.

[0003] Also, a technique for realizing an effect similar to that of a fly-eye lens with fewer optical elements has been proposed in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the technique described in Patent Document 1, unlike the case of using a fly-eye lens, since no additional configuration is required for projecting a light source image onto a specimen surface, it is possible to suppress unevenness of illumination due to the light distribution characteristics with a simpler configuration.

[0006] On the other hand, when trying to cope with extremely low magnification observation using the technique described in Patent Document 1, it is difficult to avoid increasing the size of the optical element. Since there are restrictions on the size of the optical element incorporated in an optical device such as a microscope, in the technique described in Patent Document 1, the magnification that can be handled may be substantially limited.

[0007] Based on the circumstances described above, one aspect of the present invention is to provide a technology that can suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications, from low to high. [Means for solving the problem]

[0008] An illumination optical system according to one aspect of the present invention is an illumination optical element having an optical surface directed toward a surface to be illuminated, which irradiates the surface to be illuminated in a planar manner, wherein the optical surface has a plurality of refractive surfaces formed at a constant pitch in an orthogonal direction perpendicular to the optical axis, each of which refracts light toward a predetermined area of ​​the surface to be illuminated, and a central surface intersecting the optical axis, which is provided at a position closer to the optical axis than the plurality of refractive surfaces, and the illumination optical element comprises an auxiliary lens positioned on the optical axis so as to act a positive or negative refractive force on a portion of the light beam toward the optical surface, which changes the direction of propagation of incident light so that the light emitted from the central surface becomes divergent light, and a corrective lens provided between the illumination optical element and the surface to be illuminated, which corrects the telecentricity of the light emitted as divergent light from the central surface by the action of the auxiliary lens. A lighting device according to one aspect of the present invention includes a light source, an illumination optical element having an optical surface directed toward a surface to be illuminated, which irradiates the surface to be illuminated in a planar manner, wherein the optical surface has a plurality of refractive surfaces formed at a constant pitch in a direction perpendicular to the optical axis, each refracting light toward a predetermined area of ​​the surface to be illuminated, and a central surface intersecting the optical axis, which is provided at a position closer to the optical axis than the plurality of refractive surfaces, and a Fresnel lens provided between the plurality of refractive surfaces and the light source, which collimates light from the light source, having a Fresnel lens surface provided at a ray height corresponding to the plurality of refractive surfaces, and a plane perpendicular to the optical axis at a ray height corresponding to the central surface, and a corrective lens provided between the illumination optical element and the surface to be illuminated, which irradiates the plane and the light emitted from the light source. Beauty The system includes a corrective lens that corrects the telecentricity of divergent light passing through the central plane. [Effects of the Invention]

[0009] According to the above embodiment, it is possible to suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications from low to high. [Brief explanation of the drawing]

[0010] [Figure 1] This figure illustrates the configuration of the lighting device 100 according to the first embodiment. [Figure 2] This is a diagram illustrating the operation of the illumination optical element 5. [Figure 3] This diagram illustrates the functions of auxiliary lens 3 and corrective lens 6. [Figure 4] This figure shows the settings of the lighting device 100 during low-magnification observation. [Figure 5] This figure shows the settings for the lighting device 100 during high-magnification observation. [Figure 6] This figure shows the configuration of the auxiliary lens 7 in a modified example. [Figure 7] This figure shows the configuration of the illumination optical element 8 in a modified example. [Figure 8] This figure illustrates the configuration of a modified lighting device 101. [Figure 9] This figure illustrates the configuration of the lighting device 102 according to the second embodiment. [Figure 10] This figure shows the settings for the illumination device 102 during high-magnification observation. [Figure 11] This figure shows another setting for the illumination device 102 during high-magnification observation. [Figure 12] This figure shows the settings for the illumination device 102 during low-magnification observation. [Figure 13] This figure illustrates the configuration of the lighting device 103 according to the third embodiment. [Figure 14] This figure shows the configuration of the illumination optical element 16 in a modified example. [Figure 15] This figure shows the configuration of the illumination optical element 17 in a modified example. [Figure 16] FIG. 4 is a diagram illustrating the configuration of the lighting device 104 according to the fourth embodiment. [Figure 17] FIG. 5 is a diagram showing the configuration of the illumination optical element 20 according to the modification. [Figure 18] FIG. 6 is a diagram showing the configuration of the illumination optical element 21 according to the modification. [Figure 19] FIG. 7 is a diagram illustrating the configuration of the lighting device 105 according to the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] [First Embodiment] FIG. 1 is a diagram illustrating the configuration of the lighting device 100 according to the present embodiment. FIG. 2 is a diagram for explaining the operation of the illumination optical element 5. FIG. 3 is a diagram for explaining the operations of the auxiliary lens 3 and the correction lens 6. FIG. 4 is a diagram showing the settings of the lighting device 100 during low magnification observation. FIG. 5 is a diagram showing the settings of the lighting device 100 during high magnification observation. Hereinafter, the lighting device 100 will be described with reference to FIGS. 1 to 5.

[0012] The lighting device 100 is a device that illuminates a specimen surface SP, which is an illuminated surface. The lighting device 100 can uniformly illuminate a illumination field corresponding to each magnification in a wide magnification range from low magnification (for example, less than 4 times) to high magnification by the configuration described later. Note that the lighting device 100 is, for example, a microscope lighting device used in a microscope, but it may be used not only in a microscope but also in other observation devices.

[0013] As shown in FIG. 1, the lighting device 100 includes a light source 1 that emits illumination light and an illumination optical system 10. The illumination optical system 10 is an optical system that irradiates the specimen surface SP with light from the light source 1, and includes a collimator lens 2, an auxiliary lens 3, an aperture 4, an illumination optical element 5, and a correction lens 6.

[0014] Light source 1 is, for example, a lamp light source such as a halogen lamp or an LED. Light source 1 has the light distribution characteristics illustrated in Figure 2(a). In Figure 2(a), the vertical axis is the emission angle with respect to the optical axis AX, and the horizontal axis is the emission intensity. As shown in Figure 2(a), light source 1 has light distribution characteristics that are approximately symmetrical with respect to the optical axis AX, and illumination light of different intensities is emitted from light source 1 depending on the emission angle.

[0015] The collimator lens 2 collimates the light emitted from the light source 1, converting it into parallel light. The collimator lens 2 converts the angular intensity distribution of the light emitted from the light source 1 (see Figure 2(a)) into the radial intensity distribution of the light emitted from the collimator lens 2.

[0016] The auxiliary lens 3 alters the direction of light near the optical axis AX that is emitted from the collimator lens 2. The auxiliary lens 3 is positioned between the collimator lens 2 and the illumination optical element 5, causing divergent light to enter the correction lens 6. The details of the function of the auxiliary lens 3 will be described later with reference to Figure 3.

[0017] Aperture 4 is a aperture with a changeable diameter. For example, the diameter of aperture 4 is changed according to the observation magnification. It is desirable that aperture 4 be located at the front focal position of the corrector lens 6. Details of the operation of aperture 4 will be described later with reference to Figures 4 and 5.

[0018] The illumination optical element 5 is an optical element that illuminates the surface to be illuminated (specimen surface SP) in a planar manner with light incident as parallel light. The material of the illumination optical element 5 is, for example, glass, plastic, or crystalline material (for example, quartz glass). The illumination optical element 5 has an optical surface 5a directed toward the specimen surface SP, and further has a second optical surface, optical surface 5b, on the opposite side of optical surface 5a.

[0019] Optical surface 5b is a plane perpendicular to the optical axis AX. On the other hand, optical surface 5a has a central plane CS which is both intersecting and perpendicular to the optical axis AX, and a plurality of refractive surfaces RS which each refract light toward region R1 of the specimen surface SP. The central plane CS is located closer to the optical axis AX than the plurality of refractive surfaces RS. The plurality of refractive surfaces RS are arranged in a direction perpendicular to the optical axis AX (hereinafter referred to as the perpendicular direction). Details of the operation of the illumination optical element 5 will be described later with reference to Figure 2.

[0020] The corrective lens 6 is a positive refractive lens placed between the illumination optical element 5 and the specimen surface SP, and is positioned closest to the specimen surface SP within the illumination optical system 10. The corrective lens 6 corrects the telecentricity of the light passing through the central plane CS of the illumination optical element 5. The details of the function of the corrective lens 6 will be described later with reference to Figure 3.

[0021] The configuration of the illumination optical element 5 will be explained in more detail below, with reference to Figure 2, and the operation of the illumination optical element 5 will be explained using a configuration in which the auxiliary lens 3 is omitted as an example.

[0022] As shown in Figure 2(b), the multiple refractive surfaces RS of the illumination optical element 5 are formed at a constant pitch P in the orthogonal direction. This pitch P (i.e., the orthogonal width of each of the multiple refractive surfaces RS) becomes the orthogonal width D1 of region R1.

[0023] Furthermore, as shown in Figure 2(b), the multiple refractive surfaces RS have linear shapes with different acute angles (angle θ1 ≠ θ2) in a cross-section along the optical axis AX. More specifically, the closer the refractive surface RS is to the optical axis AX, the larger the acute angle it forms with respect to the optical axis AX in a cross-section along the optical axis AX (θ1 > θ2). That is, the further the refractive surface RS is from the optical axis AX, the larger the angle it is inclined at with respect to the orthogonal direction.

[0024] Furthermore, as shown in Figure 2(b), the illumination optical element 5 is configured such that the maximum thickness t of each region where the refractive surface RS is formed is constant. Therefore, the illumination optical element 5 has deeper grooves formed by the refractive surface RS, which are further away from the optical axis AX.

[0025] When parallel light is incident on the illumination optical element 5 configured as described above from the collimator lens 2, the parallel light passes through the optical surface 5b and is incident on the optical surface 5a, where it is divided according to the refractive surface RS at which it was incident. The divided multiple beams of light (five beams in this example) are parallel beams, each having a beam diameter with a pitch P, as shown in Figure 2(b), and each has a different intensity distribution corresponding to a different emission angle range at the light source 1.

[0026] Specifically, the divided light is, for example, light having an intensity distribution I1 corresponding to an angular range from γ to β degrees with respect to the optical axis, light having an intensity distribution I2 corresponding to an angular range from β to α degrees with respect to the optical axis, light having an intensity distribution I3 corresponding to an angular range from α to -α degrees with respect to the optical axis, light having an intensity distribution I4 corresponding to an angular range from -α to -β degrees with respect to the optical axis, and light having an intensity distribution I5 corresponding to an angular range from -β to -γ degrees with respect to the optical axis.

[0027] Subsequently, of the divided light beams, the light traveling along the optical axis AX passes through the central plane CS and then through the corrective lens 6 before entering region R1. The other parallel light beams are refracted toward region R1 at each refractive surface RS, pass through the corrective lens 6, and enter region R1. In other words, the light beams divided by the illumination optical element 5 within a predetermined emission angle range overlap in region R1, as shown in Figure 2(c). As a result, the non-uniform intensity distribution caused by the light distribution characteristics is averaged out on the sample surface SP (region R1), and consequently suppressed.

[0028] The light emitted from the illumination optical element 5 as parallel light passes through the corrective lens 6 before entering region R1, and is refracted by the corrective lens 6. However, the effect of this refraction in the corrective lens 6 on the uniformity of illumination is negligible. Details of this point will be explained when describing the function of the corrective lens 6.

[0029] Thus, the illumination optical element 5 has the effect of suppressing illumination non-uniformity caused by the light distribution characteristics of the light source 1 by dividing the light distribution characteristics of the light source 1 into multiple angular ranges and superimposing them. Therefore, by using the illumination optical element 5, the specimen surface SP (illuminated surface) can be uniformly illuminated without using a fly-eye lens. Furthermore, since the illumination optical element 5 can simultaneously perform the role of a fly-eye lens as well as the role of a condenser lens used in combination with a fly-eye lens, illumination non-uniformity caused by the light distribution characteristics of the light source 1 can be easily suppressed with fewer optical elements than in conventional methods.

[0030] On the other hand, the illumination optical element 5 superimposes the divided light by refracting it inward, and furthermore, the size of the illumination field obtained by the illumination optical element 5 depends on the pitch P of the refractive surface RS. As a result, the illumination optical element 5 becomes larger as the illumination field becomes wider, and consequently the illumination device 100 also becomes larger. For this reason, for example, it is difficult to achieve uniform illumination without increasing the size of the device when observing at extremely low magnifications such as less than 4x using only the illumination optical element 5.

[0031] The lighting device 100 solves the problems at such extremely low magnification by using an auxiliary lens 3 and a corrective lens 6. The configuration of the auxiliary lens 3 and corrective lens 6 will be described in more detail below with reference to Figure 3, and the functions of the auxiliary lens 3 and corrective lens 6 will be explained.

[0032] As shown in Figure 3, the auxiliary lens 3 is a positive lens positioned between the auxiliary lens 3 and the illumination optical element 5, with the rear focal position of the auxiliary lens 3 being the focal point. More specifically, the auxiliary lens 3 is positioned such that the front focal position of the corrective lens 6 and the rear focal position of the auxiliary lens 3 substantially coincide. Furthermore, in order to avoid affecting light other than that near the optical axis AX, it is desirable that the auxiliary lens 3 has an outer diameter smaller than the outer diameter of the illumination optical element 5, for example, it may be within the diameter of the central plane CS.

[0033] As shown in Figure 3, the corrective lens 6 has a first lens surface 6a with positive refractive power that is directed toward the specimen surface SP, and a second lens surface 6b that is directed toward the illumination optical element 5. The magnitude of curvature of lens surface 6a is greater than the magnitude of curvature of lens surface 6b. The corrective lens 6 is, for example, a plano-convex lens with its convex surface directed toward the specimen surface SP, and lens surface 6b is, for example, a plane. However, lens surface 6b is not necessarily limited to a plane. It may have positive or negative refractive power as long as the refractive power is sufficiently weak. Also, lens surface 6a is not limited to a spherical shape but may be aspherical, and aberrations may be corrected well by using an aspherical shape.

[0034] In the above configuration, parallel light near the optical axis AX that enters the auxiliary lens 3 is focused by the auxiliary lens 3 at position FP, which is the rear focal point of the auxiliary lens 3. Then, it spreads out as divergent light and enters the corrector lens 6 through the optical surface 5b and central plane CS of the illumination optical element 5, which does not have refractive power. At this time, since position FP roughly coincides with the front focal point of the corrector lens 6, the light that enters the corrector lens 6 after passing through the central plane CS is converted by the corrector lens 6 into light that is approximately parallel to the optical axis AX, and illuminates a region R2 of the specimen surface SP that is wider than region R1.

[0035] In other words, the illumination device 100 ensures a wide illumination field for observation at extremely low magnification by irradiating a wide area of ​​the specimen surface SP with light near the optical axis AX, which has the highest intensity distribution, through the action of the auxiliary lens 3, and also ensures the telecentricity required for a microscope by suppressing the divergence of light incident on the specimen surface SP through the action of the corrective lens 6. Note that the difference between the rear focal position of the auxiliary lens 3 and the front focal position of the corrective lens 6 is permissible as long as the required telecentricity is satisfied, so the rear focal position of the auxiliary lens 3 and the front focal position of the corrective lens 6 do not necessarily have to coincide.

[0036] In the corrective lens 6, it is desirable to obtain most of the positive refractive power required for the corrective lens 6 from the lens surface 6a rather than the lens surface 6b. That is, it is desirable for the corrective lens 6 to have a configuration in which the lens surface 6a has a relatively large curvature. This makes it possible to prevent total internal reflection at the lens surface that occurs when the angle at which light guided to the peripheral part of the illumination field enters the corrective lens 6 is too shallow, that is, when the angle of incidence is too large, as shown in Figure 3. In general illumination devices, the lens surface of the condenser lens placed near the specimen surface SP usually has a larger curvature on the light source 1 side than on the specimen surface SP side. For this reason, it is not desirable to use a conventional condenser lens as the corrective lens 6, and it is desirable to use a corrective lens 6 that is designed separately from the condenser lens.

[0037] Furthermore, adopting a configuration in the corrector lens 6 in which the lens surface 6a has a relatively large curvature is desirable not only for preventing total internal reflection but also for achieving a high level of illumination performance for both low-magnification and high-magnification observations. The large curvature of the lens surface 6a allows the distance from the lens surface 6a to the specimen surface SP to differ significantly between the vicinity of the optical axis AX where illumination light corresponding to high-magnification observation (e.g., see Figure 2(b)) is incident and the vicinity of the outer edge of the lens where illumination light corresponding to low-magnification observation (e.g., see Figure 3) is incident. This allows for sufficient correction of the illumination position on the specimen surface SP for illumination light corresponding to low-magnification observation incident via the auxiliary lens 3, while minimizing the movement of the illumination position on the specimen surface SP for illumination light corresponding to high-magnification observation incident via the refractive surface RS. Therefore, it is possible to accommodate low-magnification observation while avoiding illumination non-uniformity caused by light from different refractive surfaces RS illuminating different regions.

[0038] Furthermore, in order to suppress the effect of the corrective lens 6 on high-magnification observation, it is desirable to position the corrective lens 6 near the specimen surface SP. This is because the closer the specimen surface SP and the corrective lens 6 are, the less the lateral movement of the light ray due to refraction at the lens surface 6a becomes, and the smaller the positional shift between the light beam refracted by multiple refractive surfaces becomes. Also, in order to suppress the effect of the corrective lens 6 on high-magnification observation, it is desirable that the positive refractive power of the corrective lens 6 is not excessively strong. That is, it is desirable that the focal length of the corrective lens 6 be somewhat long. On the other hand, in order to keep the size of the illumination optical element 5 down while ensuring the numerical aperture necessary for high-magnification observation with the illumination optical element 5, it is desirable that the illumination optical element 5 not be too far from the specimen surface SP. In order to satisfy these conditions, it is desirable that the illumination optical element 5 be positioned between the front focal position of the corrective lens 6 and the corrective lens 6.

[0039] The function of aperture 4 will be explained below with reference to Figures 1, 4, and 5. First, referring to Figure 1, it can be seen that the illumination light corresponding to high-magnification observation, which is irradiated onto the specimen surface SP via the refractive surface RS, is irradiated into region R1, while the illumination light corresponding to low-magnification observation, which is irradiated onto the specimen surface SP via the auxiliary lens 3, is irradiated into a wider region R2 that includes region R1.

[0040] Focusing on region R1, both illumination light from the refractive surface RS and illumination light from the auxiliary lens 3 illuminate the entire region R1, resulting in nearly uniform illumination. Therefore, in high-magnification observation where only region R1 is observed (i.e., the area outside region R1 is not observed), there is no need to limit the illumination light with aperture 4, and thus, as shown in Figure 1, aperture 4 can be used in its wide-open state. This allows for bright and uniform illumination of the observation range (in this case, region R1).

[0041] In contrast, focusing on region R2, with aperture 4 wide open, illumination light via the refractive surface RS is only directed to region R1, the central part of region R2, resulting in uneven illumination of the entire region R2. Therefore, in low-magnification observation of region R2 (i.e., the entire region R2 including region R1), if the numerical aperture of the observation optical system is large and the observation optical system captures illumination light via the refractive surface RS, it is desirable to use aperture 4 to block the illumination light via the refractive surface RS. As shown in Figure 4, it is desirable to use aperture 4 with its aperture diameter stopped down to approximately the outer diameter of the auxiliary lens 3. This allows for uniform illumination of a wide observation area (in this case, region R2).

[0042] Furthermore, if the auxiliary lens 3 is detachably mounted in the optical path, it may be removed from the optical path during high-magnification observation, as shown in Figure 5. This allows the illumination light that was illuminating region R2 via the auxiliary lens 3 to be concentrated on region R1. As a result, brighter illumination can be achieved compared to the case shown in Figure 1.

[0043] As described above, the illumination device 100 can suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications, from low to high. Therefore, it is suitable as an illumination device for use in observation devices that are used at various observation magnifications, from low to high, such as microscopes.

[0044] Figure 6 shows the configuration of the auxiliary lens 7 according to a modified example. In the example described above, an auxiliary lens 3 was shown with an outer diameter smaller than the outer diameter of the illumination optical element 5 and approximately the diameter of the central plane CS, so as not to obstruct the incidence of illumination light to the refractive surface RS. However, the outer diameter of the auxiliary lens 3 is not limited to approximately the diameter of the central plane CS.

[0045] The illumination device 100 may be equipped with an auxiliary lens 7 instead of the auxiliary lens 3. The auxiliary lens 7 has a structure in which a convex portion 7a, corresponding to the auxiliary lens 3 which has a positive refractive power, is supported by a parallel plate 7b. By providing the parallel plate b, the auxiliary lens 7 can be stably positioned at a desired location within the illumination device 100. Furthermore, since the portion through which the illumination light incident on the refractive surface RS is transmitted is made up of the parallel plate 7b, the influence on the illumination light incident on the refractive surface RS can be minimized.

[0046] Figure 7 shows the configuration of the illumination optical element 8 according to a modified example. In the example described above, the auxiliary lens 3 and the illumination optical element 5 were provided separately within the illumination device 100, but the auxiliary lens 3 may be formed integrally with the illumination optical element 5.

[0047] The illumination device 100 may include an illumination optical element 8 instead of the auxiliary lens 3 and illumination optical element 5. The illumination optical element 8 has an optical surface 8a having multiple refractive surfaces corresponding to the optical surface 5a of the illumination optical element 5, and further has a convex portion 8b corresponding to the auxiliary lens 3 on the optical surface opposite to the optical surface 8a. By using the illumination optical element 8, the number of parts can be reduced, which simplifies the assembly process and lowers manufacturing costs.

[0048] Figure 8 illustrates the configuration of a modified illumination device 101. Illumination device 101 differs from illumination device 100 in that it includes an illumination optical system 11 instead of an illumination optical system 10. Illumination optical system 11 differs from illumination optical system 10 in that it includes a diffuser plate 9 between the collimator lens 2 and the auxiliary lens 3. In illumination device 101, the diffuser plate 9 diffuses the illumination light, thereby suppressing the uneven distribution of the illumination light intensity. As a result, illumination device 101 can further suppress the unevenness of illumination caused by the light distribution characteristics of the light source compared to illumination device 100.

[0049] [Second Embodiment] Figure 9 is a diagram illustrating the configuration of the illumination device 102 according to this embodiment. Figure 10 shows the settings of the illumination device 102 during high-magnification observation. Figure 11 shows another setting of the illumination device 102 during high-magnification observation. Figure 12 shows the settings of the illumination device 102 during low-magnification observation. The illumination device 102 will be described below with reference to Figures 1 to 5.

[0050] The illumination device 102, like the illumination device 100, is a device that illuminates the specimen surface SP, which is the surface to be illuminated, and is also like the illumination device 100 in that it can uniformly illuminate the illumination field corresponding to each magnification over a wide magnification range from low magnification (for example, less than 4x) to high magnification.

[0051] While the illumination device 100 is configured to change the illumination range in two stages, low magnification (e.g., 2x) and high magnification (e.g., 10x), the illumination device 102 differs from the illumination device 100 in that it can change the illumination range in a total of four stages, including low magnification (e.g., 2x), high magnification (e.g., 10x), a second high magnification (e.g., 20x), and a third high magnification (e.g., 40x). Specifically, the illumination device 102 differs from the illumination device 100 in that it has an illumination optical system 12 instead of an illumination optical system 10. Furthermore, the illumination optical system 12 differs from the illumination optical system 10 in that it has an illumination optical element 15 instead of an illumination optical element 5.

[0052] The illumination optical element 15 is an optical element that illuminates the specimen surface SP in a planar manner with light incident as parallel light. The illumination optical element 15 has an optical surface 15a directed toward the specimen surface SP, and further has a second optical surface 15b on the opposite side of optical surface 15a.

[0053] Optical surface 15b is a plane perpendicular to the optical axis AX, and is the same as optical surface 5b. On the other hand, optical surface 15a has a central plane CS which is a plane that intersects and is perpendicular to the optical axis AX, and a plurality of refractive surfaces RS1 which are formed at a constant pitch in an orthogonal direction and each refracts light toward region R11 of the specimen surface SP. This configuration is the same as that of optical surface 5a.

[0054] The optical surface 15a further has multiple refractive surfaces RS2, which are formed at a constant pitch in an orthogonal direction and located further from the optical axis AX in a direction orthogonal to the multiple refractive surfaces RS1, and each of these surfaces refracts light toward region R12. Since the pitch at which the multiple refractive surfaces RS2 are formed is shorter than the pitch at which the multiple refractive surfaces RS1 are formed, region R12 is part of region R11.

[0055] Furthermore, the optical surface 15a has multiple refractive surfaces RS3 that are formed at a constant pitch in an orthogonal direction, at positions further from the optical axis AX in an orthogonal direction than the multiple refractive surfaces RS2, and each of them refracts light toward region R13. Since the pitch at which the multiple refractive surfaces RS3 are formed is shorter than the pitch at which the multiple refractive surfaces RS2 are formed, region R13 is part of region R12.

[0056] Thus, the optical surface 15a differs from the optical surface 5a in that, in addition to the multiple refractive surfaces RS1 that correspond to the multiple refractive surfaces RS of the optical surface 5a of the illumination optical element 5, it also has multiple refractive surfaces (refracting surfaces RS2, RS3) on its outside.

[0057] The reason for shortening the pitch as you move away from the optical axis is that generally, higher magnification observations require a larger numerical aperture. Therefore, as long as the required numerical aperture can be secured, the pitch of the outer refractive planes does not necessarily have to be shorter than that of the inner refractive planes.

[0058] Since region R13 is illuminated by both the illumination light via the auxiliary lens 3 and the illumination light via the refractive surface, the entire region R13 is illuminated almost uniformly. Therefore, for the third high-magnification observation of region R13 (for example, 40x), it is sufficient to use the aperture 4 in its widest setting, as shown in Figure 9. This allows the observation area (in this case, region R13) to be brightly and uniformly illuminated.

[0059] In region R12, with aperture 4 open, illumination light via refractive surface RS3 only illuminates region R13, the central part of region R12, resulting in uneven illumination of the entire region R12. Therefore, in a second high-magnification observation (e.g., 20x) to observe region R12 (i.e., the entire region R12 including region R13), if the numerical aperture of the observation optical system is large and the observation optical system captures illumination light via refractive surface RS3, it is desirable to use aperture 4 to block the illumination light via refractive surface RS3. As shown in Figure 10, it is desirable to use aperture 4 with its aperture diameter stopped down to the inside of the refractive surface RS3. This allows for uniform illumination of the observation range (in this case, region R12).

[0060] In region R11, with aperture 4 open, illumination light from refractive surfaces other than refractive surface RS1 (refracting surfaces RS2 and RS3) is only irradiated to the central part of region R11 (regions R12 and R13), resulting in uneven illumination of the entire region R11. Therefore, in high-magnification observation (e.g., 10x) of region R11 (i.e., the entire region R11 including regions R12 and R13), if the numerical aperture of the observation optical system is large and the observation optical system captures illumination light from refractive surfaces RS2 and RS3, it is desirable to use aperture 4 to block the illumination light from refractive surfaces RS3 and RS2. As shown in Figure 11, it is desirable to use aperture 4 with its aperture diameter stopped down to the inside of refractive surface RS2. This allows for uniform illumination of the observation range (in this case, region R11).

[0061] In region R14, with aperture 4 open, illumination light via the refractive surface is only illuminating the central part of region R14 (regions R11, R12, and R13), resulting in uneven illumination of the entire region R14. Therefore, in low-magnification observation of region R14 (i.e., the entire region R14 including regions R11, R12, and R13), if the numerical aperture of the observation optical system is large and the observation optical system captures illumination light via refractive surfaces RS1, RS2, and RS3, it is desirable to use aperture 4 to block the illumination light via the refractive surfaces. As shown in Figure 12, it is desirable to use aperture 4 with its aperture diameter stopped down to the inside of refractive surface RS1. This allows for uniform illumination of the observation range (in this case, region R14).

[0062] As described above, the illumination device 102 can suppress illumination non-uniformity caused by the light distribution characteristics of the light source across a wide range of observation magnifications, from low to high. In particular, the illumination device 102 can accommodate multiple different magnifications during high-magnification observation.

[0063] [Third Embodiment] Figure 13 is a diagram illustrating the configuration of the lighting device 103 according to this embodiment. The lighting device 103 will be described below with reference to Figure 13.

[0064] The illumination device 103, like the illumination device 100, is a device that illuminates the specimen surface SP, which is the surface to be illuminated, and is also similar to the illumination device 100 in that it can uniformly illuminate the illumination field corresponding to each magnification over a wide magnification range from low magnification (for example, less than 4x) to high magnification.

[0065] The illumination device 103 differs from the illumination device 100 in that it has an illumination optical system 13 instead of an illumination optical system 10. Furthermore, the illumination optical system 13 differs from the illumination optical system 10 in that it has an auxiliary lens 14 instead of an auxiliary lens 3.

[0066] The auxiliary lens 14 is positioned similarly to the auxiliary lens 3 in that its rear focal position is approximately the same as that of the corrective lens 6. However, unlike the auxiliary lens 3, the auxiliary lens 14 is a negative lens and is positioned between its rear focal position and the illumination optical element. The auxiliary lens 14 may also be bonded to the optical surface 5b of the illumination optical element 5, as shown in Figure 13.

[0067] The auxiliary lens 14 converts the parallel light incident on it into divergent light using its negative refractive power. The divergent light emitted from the auxiliary lens 14 passes through the central plane CS of the illumination optical element 5 and is incident on the corrective lens 6, where it is converted into approximately parallel light and irradiates region R2 of the specimen surface SP.

[0068] As described above, the illumination device 103, like the illumination device 100, can suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications from low to high. Furthermore, by using a negative lens as an auxiliary lens, the overall length of the illumination device 103 can be reduced compared to the illumination device 100.

[0069] Figure 14 shows the configuration of a modified illumination optical element 16. Figure 15 shows the configuration of a modified illumination optical element 17. In the example described above, the auxiliary lens 14 is shown to be bonded to the plane (optical surface 5b) of the illumination optical element 5, but a curved surface corresponding to the auxiliary lens may be provided on a part of the optical surface of the illumination optical element. That is, the illumination optical element and the auxiliary lens may be formed integrally.

[0070] The illumination device 103 may include an illumination optical element 16 as shown in Figure 14 instead of the auxiliary lens 14 and illumination optical element 5. The illumination optical element 16 has an optical surface 16a having multiple refractive surfaces corresponding to the optical surface 5a of the illumination optical element 5, and further has a concave surface S1 corresponding to the auxiliary lens 14 on the optical surface 16b opposite to the optical surface 16a. The optical surface 16b has a concave surface S1 provided at a position corresponding to the central surface CS, and a flat surface S0.

[0071] The illumination device 103 may include an illumination optical element 17 as shown in Figure 15 instead of the auxiliary lens 14 and illumination optical element 5. The illumination optical element 17 has an optical surface 17a having multiple refractive surfaces, and further has an optical surface 17b opposite to optical surface 17a. Optical surface 17b is a plane perpendicular to the optical axis AX. Optical surface 17a differs from optical surface 5a in that it has a concave surface S2 instead of a central surface CS.

[0072] By using illumination optical element 16 or illumination optical element 17, the number of parts can be reduced, thereby simplifying the assembly process and lowering manufacturing costs.

[0073] [Fourth Embodiment] Figure 16 is a diagram illustrating the configuration of the lighting device 104 according to this embodiment. The lighting device 104 will be described below with reference to Figure 16.

[0074] The illumination device 104, like the illumination device 100, is a device that illuminates the specimen surface SP, which is the surface to be illuminated, and is also similar to the illumination device 100 in that it can uniformly illuminate the illumination field corresponding to each magnification over a wide magnification range from low magnification (for example, less than 4x) to high magnification.

[0075] The illumination device 104 differs from the illumination device 100 in that it has an illumination optical system 19 instead of the illumination optical system 10. The illumination optical system 19 differs from the illumination optical system 10 in that it has an illumination optical element 18 instead of the collimator lens 2, auxiliary lens 3, and illumination optical element 5.

[0076] The illumination optical element 18 has an optical surface 18a with multiple refractive surfaces, and further has an optical surface 18b opposite to optical surface 18a. Optical surface 18b is a Fresnel lens surface that functions as a collimator lens. Optical surface 18a differs from optical surface 5a in that it has a concave surface S3 instead of a central surface CS. The negative refractive power of the concave surface S3 plays a role in causing divergent light to enter the corrective lens 6, similar to the auxiliary lens 3.

[0077] As described above, the illumination optical system 19 acts in the same way as the illumination optical system 10 with respect to the light emitted from the light source 1. Therefore, the illumination device 104, like the illumination device 100, can suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications from low to high.

[0078] Furthermore, by using a Fresnel lens surface (optical surface 18b) instead of the collimator lens 2, and a concave surface S3 instead of the auxiliary lens 3, the illumination optical element 18 can perform the roles of both the collimator lens 2 and the auxiliary lens 3, thereby reducing the number of parts. This simplifies the assembly process and reduces manufacturing costs. In addition, the overall length of the illumination device 104 can be kept short.

[0079] Figure 17 shows the configuration of the illumination optical element 20 according to a modified example. Figure 18 shows the configuration of the illumination optical element 21 according to a modified example. In the example described above, an example was shown in which the auxiliary lens 3 can be omitted by providing a concave surface S3 on the illumination optical element 18, but the auxiliary lens 3 may also be omitted by providing a convex surface on the illumination optical element.

[0080] The illumination device 104 may include an illumination optical element 20 as shown in Figure 17 instead of the illumination optical element 18. The illumination optical element 20 has an optical surface 20a having multiple refractive surfaces corresponding to the optical surface 5a of the illumination optical element 5, and further has an optical surface 20b opposite to optical surface 20a. The optical surface 20b has a Fresnel lens surface FrS corresponding to the collimator lens 2 and a convex surface S4 corresponding to the auxiliary lens 3. The convex surface S4 has a rear focal position at position FP, which is the front focal position of the corrective lens 6.

[0081] Furthermore, the illumination device 104 may include an illumination optical element 21, as shown in Figure 18, instead of the illumination optical element 18. The illumination optical element 21 has an optical surface 21a having multiple refractive surfaces corresponding to the optical surface 5a of the illumination optical element 5, and also has an optical surface 21b opposite to the optical surface 21a. The illumination optical element 21 differs from the illumination optical element 20 in that the rear focal point position (position FP) of the convex surface of the optical surface 21b is located within the illumination optical element 21. Other aspects are the same as those of the illumination optical element 20.

[0082] [Fifth Embodiment] Figure 19 is a diagram illustrating the configuration of the lighting device 105 according to this embodiment. The lighting device 105 will be described below with reference to Figure 19.

[0083] The illumination device 105, like the illumination device 100, is a device that illuminates the specimen surface SP, which is the surface to be illuminated, and is also like the illumination device 100 in that it can uniformly illuminate the illumination field corresponding to each magnification over a wide magnification range from low magnification (for example, less than 4x) to high magnification.

[0084] The illumination device 105 differs from the illumination device 100 in that it includes an illumination optical system 23 instead of the illumination optical system 10. The illumination optical system 23 differs from the illumination optical system 10 in that it includes an illumination optical element 22 instead of the collimator lens 2, auxiliary lens 3, and illumination optical element 5, and the light source 1 is positioned at the front focal position of the corrective lens 6.

[0085] The illumination optical element 22 has an optical surface 22a having multiple refractive surfaces, and further has an optical surface 22b opposite to optical surface 22a. Optical surface 22a has a central surface CS and multiple refractive surfaces RS, similar to the optical surface 5a of the illumination optical element 5. Optical surface 22b has a Fresnel lens surface FrS corresponding to the collimator lens 2 and a plane S0 perpendicular to the optical axis AX. Optical surface 22b has the Fresnel lens surface FrS at a ray height corresponding to the multiple refractive surfaces RS of optical surface 22a, and the plane S0 at a ray height corresponding to the central surface CS.

[0086] In the illumination optical system 23, the illumination optical element 22 functions similarly to the collimator lens 2 by collimating the light from the light source 1 with the Fresnel lens surface FrS. Therefore, the collimator lens 2 can be omitted. Furthermore, by providing a plane S0 at the position of the optical surface 22b corresponding to the central plane CS, the divergent light from the light source 1 is directly incident on the corrective lens 6. Moreover, by positioning the light source 1 at the front focal position of the corrective lens 6, the divergent light incident on the corrective lens 6 is collimated by the corrective lens 6. Therefore, the auxiliary lens 3 can be omitted.

[0087] As described above, the illumination optical system 23 acts in the same way as the illumination optical system 10 with respect to the light emitted from the light source 1. Therefore, the illumination device 105, like the illumination device 100, can suppress illumination non-uniformity caused by the light distribution characteristics of the light source over a wide range of observation magnifications from low to high.

[0088] Furthermore, similar to the lighting device 104, the number of parts can be reduced by omitting the collimator lens 2 and the auxiliary lens 3, which simplifies the assembly process and reduces manufacturing costs, and also allows for a shorter overall length of the lighting device 105.

[0089] The embodiments described above are specific examples provided to facilitate understanding of the invention, and the present invention is not limited to these embodiments. Modified forms of the embodiments described above and alternative forms that replace the embodiments described above may be included. In other words, each embodiment can be modified in terms of its components without departing from its spirit and scope. Furthermore, new embodiments can be implemented by appropriately combining multiple components disclosed in one or more embodiments. In addition, some components may be deleted from the components shown in each embodiment, or some components may be added to the components shown in an embodiment. Moreover, the processing procedures shown in each embodiment may be performed in a different order, as long as they do not contradict each other. That is, the illumination optical system and illumination device of the present invention can be modified in various ways without departing from the scope of the claims.

[0090] In the embodiments described above, an example was shown in which uniformity of illumination within the illumination range according to the observation magnification was ensured by changing the aperture diameter of the diaphragm. However, adjusting the diaphragm according to the observation magnification is not always necessary. In the examples described above, the diaphragm is used to ensure uniformity of illumination within the illumination range by blocking light with a high numerical aperture. However, since the pupil diameter of a low-magnification objective lens is smaller than that of a high-magnification objective lens, light with an unnecessarily high numerical aperture will be vignetted within the observation optical system including the objective lens. For this reason, even if uniformity of illumination is not necessarily maintained, it is possible to avoid the effects of illumination inhomogeneity on the image plane. [Explanation of symbols]

[0091] 100-105 Lighting equipment 1 light source 2. Collimator lens 3. Auxiliary lens 4 aperture 5, 8, 15-18, 20-22 Illumination optical elements 6 Correction lenses 7, 14 Auxiliary lenses 7b parallel plate 9. Diffuser 10~13, 19, 23 Illumination optical system AX optical axis CS center plane FS plane I1~I5 intensity distribution P pitch R1, R2, R11~R14 area S1~S3 concave S4 Convex SP specimen surface RS, RS1~RS3 refractive surfaces

Claims

1. An illumination optical element having an optical surface directed toward the surface to be illuminated, which irradiates light onto the surface to be illuminated in a planar manner, The optical surface is Multiple refractive surfaces formed at a constant pitch in a direction perpendicular to the optical axis, each refracting light toward a predetermined area of ​​the illuminated surface, A central surface intersecting the optical axis, provided at a position closer to the optical axis than the plurality of refractive surfaces, An illumination optical element comprising, An auxiliary lens positioned on the optical axis to apply a positive or negative refractive force to a portion of the light beam directed toward the optical surface, the auxiliary lens changing the direction of incident light so that the light emitted from the central surface becomes divergent light, The system includes a corrective lens provided between the illumination optical element and the illuminated surface, which corrects the telecentricity of the light emitted as divergent light from the central surface by the action of the auxiliary lens. An illumination optical system characterized by the following features.

2. In the illumination optical system according to claim 1, The aforementioned corrective lens is A first lens surface having positive refractive power directed toward the illuminated surface, It has a second lens surface directed toward the illumination optical element, The magnitude of the curvature of the first lens surface is greater than the magnitude of the curvature of the second lens surface. An illumination optical system characterized by the following features.

3. In the illumination optical system described in claim 2, The first lens surface has an aspherical shape. An illumination optical system characterized by the following features.

4. In the illumination optical system according to any one of claims 1 to 3, The corrective lens is a plano-convex lens with its convex surface facing the illuminated surface. An illumination optical system characterized by the following features.

5. In the illumination optical system according to any one of claims 1 to 4, The illumination optical element is positioned between the front focal position of the corrector lens and the corrector lens. An illumination optical system characterized by the following features.

6. In the illumination optical system according to any one of claims 1 to 5, further, The illumination optical element is positioned between the rear focal position of the auxiliary lens and the corrective lens. An illumination optical system characterized by the following features.

7. In the illumination optical system according to claim 6, The auxiliary lens is a positive lens having the rear focal position of the auxiliary lens, positioned between the auxiliary lens and the illumination optical element. An illumination optical system characterized by the following features.

8. In the illumination optical system according to claim 6, The auxiliary lens is a negative lens positioned between the rear focal point of the auxiliary lens and the illumination optical element. An illumination optical system characterized by the following features.

9. In the illumination optical system according to any one of claims 6 to 8, The outer diameter of the auxiliary lens is smaller than the outer diameter of the illumination optical element. An illumination optical system characterized by the following features.

10. In the illumination optical system according to claim 9, The outer diameter of the auxiliary lens is within the diameter of the central surface. An illumination optical system characterized by the following features.

11. In the illumination optical system according to any one of claims 6 to 10, The auxiliary lens is positioned such that the front focal position of the corrective lens and the rear focal position of the auxiliary lens substantially coincide. An illumination optical system characterized by the following features.

12. In the illumination optical system according to any one of claims 6 to 10, The auxiliary lens is formed integrally with the illumination optical element. An illumination optical system characterized by the following features.

13. In the illumination optical system according to any one of claims 1 to 12, further, The corrective lens is equipped with an aperture positioned at the front focal point. An illumination optical system characterized by the following features.

14. In the illumination optical system according to any one of claims 1 to 13, The plurality of refractive surfaces have linear shapes with different angles in a cross-section along the optical axis, The closer the refractive surface is to the optical axis, the larger the angle it makes with the optical axis in a cross-section along the optical axis. An illumination optical system characterized by the following features.

15. In the illumination optical system according to any one of claims 1 to 14, The optical surface further, The plurality of second refractive surfaces are located further from the optical axis in the direction perpendicular to the plurality of refractive surfaces, and are formed at a constant pitch in the direction perpendicular to the plurality of refractive surfaces, each of which refracts light toward a part of the predetermined region, The pitch at which the plurality of second refractive surfaces are formed is shorter than the pitch at which the plurality of refractive surfaces are formed. An illumination optical system characterized by the following features.

16. In the illumination optical system according to any one of claims 1 to 15, further, A collimator lens is provided between the light source that emits light to illuminate the surface to be illuminated and the illumination optical element. An illumination optical system characterized by the following features.

17. In the illumination optical system according to claim 16, The collimator lens is a Fresnel lens. An illumination optical system characterized by the following features.

18. In the illumination optical system according to claim 17, The Fresnel lens is formed integrally with the illumination optical element. An illumination optical system characterized by the following features.

19. An illumination optical system according to any one of claims 1 to 18, Equipped with a light source, A lighting device characterized by the following features.

20. Light source and An illumination optical element having an optical surface directed toward the surface to be illuminated, which irradiates light onto the surface to be illuminated in a planar manner, The optical surface is Multiple refractive surfaces formed at a constant pitch in a direction perpendicular to the optical axis, each refracting light toward a predetermined area of ​​the illuminated surface, A central surface intersecting the optical axis, provided at a position closer to the optical axis than the plurality of refractive surfaces, An illumination optical element comprising, A Fresnel lens is provided between the plurality of refractive surfaces and the light source to collimate light from the light source, A Fresnel lens surface provided at a position corresponding to the light ray height of the plurality of refractive surfaces, A Fresnel lens having a plane perpendicular to the optical axis at a position corresponding to the ray height of the central plane, The system includes a corrective lens provided between the illumination optical element and the illuminated surface, which corrects the telecentricity of divergent light emitted from the light source and passing through the plane and the central plane. A lighting device characterized by the following features.

21. In the lighting device according to claim 20, The light source is positioned at the front focal point of the corrective lens. A lighting device characterized by the following features.

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