Lighting device for total internal reflection of light

Abstract

Lighting device for total internal reflection of light for generating evanescent light (L3) by illuminating an object (8) with light (L2), wherein the lighting device for total internal reflection of light (1) comprises: a light source (2) for providing illumination light (L1); a spatial light modulator (4) for inputting the illumination light (L1), and for modulating the illumination light (L1) by means of a lens pattern (P1); an objective lens (5) for illuminating an object surface with the modulated illumination light (L2) and thereby generating total internal reflection; and a computation unit (41) for providing the lens pattern (P1) according to a desired polarization state of the evanescent light (L3) to the spatial light modulator (4), wherein The lens pattern (P1) provided by the computation unit (41) is a pattern for focusing the illumination light (L2) at a position on a pupil plane of the objective lens (5) according to the desired polarization state of the evanescent light (L3).

Description

Technical field

[0001] The present invention relates to a lighting device for the total internal reflection of light. State of the art

[0002] Evanescent light, which occurs during total internal reflection, is able to selectively illuminate only the vicinity of a total internal reflection interface and drastically reduce background light from regions other than the illuminated area. Therefore, a total internal reflection illumination device is used for most microscopic observations of extremely thin objects, such as cells (see, for example, patent literature 1).

[0003] For a microscope that uses an illumination device for total internal reflection of light, an illumination technique is disclosed in which a diffraction-diffusion plate is employed so that evanescent light with all polarization directions is generated in three dimensions, thus enabling the observation of a sample regardless of its orientation (Patent Reference 2). Furthermore, another illumination technique is disclosed in which a micromirror actuator (Digital Micromirror Device, DMD) or the like is used, thereby generating ring-shaped light, which enables the effective use of evanescent light (Patent References 3 and 4).Furthermore, another illumination technique is disclosed in which a spatial light modulator and a lens are combined and two light focusing points are provided at arbitrary positions on a pupil incidence plane, so that an area of ​​a sample is illuminated in a striped pattern (non-patent literature 1). List of quotations Patent literature Patent literature 1: Publication of the Japanese patent application JP 2004 - 309 785 A Patent literature 2: Publication of the Japanese patent application JP 2004 - 138 735 A Patent literature 3: Publication of the Japanese patent application JP 2000 - 81 383 A Patent literature 4: Publication of the Japanese patent application JP 2006 - 275 685 A Patent literature 5: Publication of the Japanese patent application JP 2006 - 276 377 A Patent literature 6: DE 11 2012 005 960 T5 Patent literature 7: US 2010 / 0 141 939 A1 Non-patented literature

[0004] Non-patent literature 1: R. Fiolka et al., “Structured Illumination in total internal reflection fluorescence microscopy using a spatial light modulator,” Optics Letters, USA, Optical Society of America, July 2008, Vol. 33, No. 14, pp. 1629-1631. Summary of the invention; Technical task

[0005] In a total internal reflection illumination device used to illuminate an object with evanescent light, it is desirable to be able to arbitrarily control the polarization state, penetration length, shape, or intensity of the evanescent light. This is because arbitrary control allows for the implementation of various illumination modes. However, if the illumination device is used, for example, in conventional total internal reflection microscopes with a diffraction plate, a mechanical mechanism for the diffraction plate is required, resulting in a complex configuration and making it difficult to switch the illumination conditions of the evanescent light.

[0006] The present invention aims to solve the problem described above and states as its objective the provision of an illumination device for the total reflection of light with which a polarization state, a penetration length, shape and light intensity of evanescent light can be set with a simple configuration. Technical solution

[0007] To solve the problem described above, a total internal reflection lighting device according to the present invention generates evanescent light by illuminating an object with light, wherein the total internal reflection lighting device is defined in claim 1.

[0008] The presenting inventors have discovered that when the illumination light is focused on the pupil plane of the objective lens in the total internal reflection illumination device, varying the focusing shape or position of the light leads to a significant change in the polarization status, penetration length, shape, or intensity of the evanescent light. Furthermore, in this total internal reflection illumination device, an electronic command from the processing unit causes the lens pattern to be displayed on the spatial light modulator, thus allowing the focusing shape or position on the pupil plane of the objective lens to be easily changed.

[0009] Thus, for example, evanescent light with the desired polarization can be achieved from a P-polarization and an S-polarization according to the polarization dependence of the object. Furthermore, evanescent light with a desired penetration length, shape, or light intensity can be achieved according to the object's properties such as thickness, concentration, or the like. In this way, the total internal reflection illumination device, as described above, allows for easy adjustment of the polarization state, penetration length, shape, and light intensity of the evanescent light with a simple configuration. Advantageous effects of the invention

[0010] According to a total reflection lighting device according to the present invention, a total reflection lighting device can be provided with a simple configuration with which a polarization state, penetration length, shape and light intensity of evanescent light can be adjusted. Brief description of the drawings Fig. Figure 1 shows a configuration of a lighting device for total internal reflection of light according to the present embodiment. Fig. Figure 2 shows in drawings (a) and (b) the illumination light L2 when the illumination light is focused to a point shape on a pupil plane. Fig. Figure 3 shows in drawings (a) and (b) the illumination light L2 when the illumination light is focused into a ring shape on the pupil plane. Fig. Figure 4 shows in drawings (a) and (b) a comparison of the illumination areas in plane illumination and point illumination. Fig. Figure 5 shows a Fresnel lens pattern for plane illumination as an example of the Fresnel lens pattern. Fig. Figure 6 shows in drawing (a) and (b) a total reflection mode of the illumination light in the plane illumination. Fig. Figure 7 shows in drawing (a) and (b) the principle of the polarization process of illumination light. Fig. Figure 8 is a visualization of a relationship between an angle on the pupil plane and a polarization plane of the illumination light. Fig. Figure 9 shows in drawings (a) - (d) a relationship between a light intensity and a penetration length of evanescent light and a position of a focusing point on the pupil plane. Fig. Figure 10 shows in drawing (a) and (b) a configuration with two focusing points on the pupil plane. Fig. Figure 11 is a representation of a Fresnel lens pattern to provide two focusing points on a pupil plane 9. Fig. Figure 12 shows in drawing (a) and (b) the observation results of interference fringes when two focusing points are present on the pupil plane 9. Fig. Figure 13 shows in drawing (a) - (c) the observation results of interference fringes of evanescent light when eight focusing points are present on the pupil plane 9. Fig. Figure 14 shows an observation result of illumination light passing through an object substrate when the angle of incidence θ of the illumination light is zero degrees. Fig. Figure 15 shows a toroidal Fresnel lens pattern as an example of the Fresnel lens pattern for spot illumination in a ring-shaped focusing mode. Fig. Figure 16 shows in (a) and (b) observation results of the point illumination in the ring-shaped focusing mode. Fig. Figure 17 shows a NA value dependence of the light intensity of evanescent light. Fig. Figure 18 shows in drawing (a) - (f) a beam shape of evanescent light in point illumination in the ring-shaped focusing mode. Fig. Figure 19 shows the decision processes of the Fresnel lens pattern in plane illumination and point illumination. Description of the exemplary implementations

[0011] The following section describes exemplary embodiments of the lighting device for total internal reflection of light in detail, with reference to the accompanying drawings. In the description, the same elements are identified with the same reference symbols without unnecessary description.

[0012] Fig. Figure 1 shows a configuration of a total internal reflection lighting device according to the present embodiment. A total internal reflection lighting device 1 comprises a light source 2 for providing illumination L1, a focusing lens 3, a spatial light modulator 4, an objective lens 5, an object substrate 6, and a processing unit 41. The spatial light modulator 4 is optically connected to the light source 2, while the focusing lens 3 is arranged on an optical axis between the light source 2 and the spatial light modulator 4. The object substrate 6 comprises an illumination light receiving surface 6a and an object mounting surface 6b, and the illumination light receiving surface 6a is oriented towards the objective lens 5, while the object mounting surface 6b is arranged on the opposite side of the illumination light receiving surface 6a.The object substrate 6 is optically connected to the spatial light modulator 4, while the objective lens 5 is arranged between the object substrate 6 and the spatial light modulator 4.

[0013] The computing unit 41 includes an input unit 42 and a display unit 43, and the input unit 42 and the display unit 43 are electrically connected to a main unit of the computing unit 41. The computing unit 41 is electrically connected to the spatial light modulator 4. Immersion oil 7 with a refractive index equal to that of the object substrate 6 is arranged between the objective lens 5 and the object substrate 6. An object 8 is placed on the object mounting surface 6b. The dashed line in the figure represents a pupil plane 9 of the objective lens 5.

[0014] The illumination light L1 is emitted by the light source 2, then passes through the focusing lens 3 and reaches the spatial light modulator 4. The illumination light L1 is modulated by the spatial light modulator 4, and after modulation, the illumination light L2 passes through the objective lens 5 and enters the object substrate 6 at a predetermined angle. After modulation, the illumination light L2 undergoes total internal reflection by the object substrate 6, and evanescent light L3 emerges from the object mounting surface 6b and illuminates the object 8. Since the object 8 is placed on the object mounting surface 6b, the incident illumination light L2 has the same effect on the object substrate 6 as the directly incident illumination light L2 on a surface of the object 8.

[0015] A lens pattern P1 is provided by the computation unit 41 for the spatial light modulator 4. The lens pattern P1 is a pattern with a lensing effect and can, for example, be a Fresnel lens pattern, a toroidal lens pattern, or a toroidal Fresnel lens pattern. Furthermore, the lens pattern can be a Fresnel lens pattern superimposed with a desired pattern. A case in which the Fresnel lens pattern is used as the lens pattern P1 is described below.

[0016] If a phase value on a coordinate (x, y) is represented by Φ(x, y), the Fresnel lens pattern P1 is expressed by formula (1). [Formula 1] ϕ(x,y)=π((x−x0)2+(y−y0)2)fλ[rad.]

[0017] The values ​​x0 and y0 represent coordinates (hereinafter referred to as the center coordinates) corresponding to the center point 5. Furthermore, the values ​​f and λ represent a focal length of the objective lens 5 and a wavelength of the illumination light L2, respectively. The Fresnel lens pattern P1 is generated using formula (1) and displayed on the spatial light modulator 4, so that the illumination light L1 is output in a focused beam. In the present embodiment, the illumination light L2 is focused on the pupil plane 9 in a focusing mode such as a point or ring focusing mode. (a) and (b) in Fig. Figures 2 show the illumination light L2 when the illumination light L2 is focused into a point shape on the pupil plane 9. (a) in Fig. Figure 2 shows a configuration of the lighting device 1 for total internal reflection of light from Fig. 1, and (b) in Fig. Figure 2 shows the pupil plane 9 from the direction of the optical axis of the illumination light L2, with a region 9A contained in the pupil plane 9. Region 9A represents a surface through which the illumination light L2 passes to produce total internal reflection. In the point-like focusing mode, the illumination light L2 is focused to a point shape at a position on the pupil plane 9, as shown in (b). Fig. Figure 2 illustrates this. A point where the optical path of the illumination light L2 and the pupil plane 9 intersect is subsequently referred to as a focusing point F1. After focusing on the pupil plane 9, the illumination light L2 is refracted by the objective lens 5 to become parallel light and illuminates the object substrate 6. The evanescent light L3 emerging from the object substrate 6 illuminates a larger area of ​​the object 8 compared to the annular focusing mode described later. Illumination with the evanescent light L3 in the point focusing mode is subsequently referred to as plane illumination. (a) and (b) in Fig. Figure 3 shows the illumination light L2 when the illumination light L2 is focused into a ring shape on the pupil plane 9. (a) in Fig. Figure 3 shows a configuration of the lighting device 1 for total internal reflection of light from Fig. 1, and (b) in Fig. Figure 3 shows the pupil plane 9 from the direction of the optical axis of the illumination light L2, with region 9A contained in the pupil plane 9. In the annular focusing mode, the illumination light L2 is focused into the ring shape at a position on the pupil plane 9, as shown in (b). Fig. Figure 3 illustrates this. A ring at which the optical path of the illumination light L2 and the pupil plane 9 intersect is subsequently referred to as a focusing ring F2. After focusing on the pupil plane 9, the illumination light L2 is oriented by the objective lens 5 into annular, parallel light and illuminates the object substrate 6. As the annular parallel light approaches the object substrate 6, its outer diameter decreases, and the respective circumferential portions overlap on the object substrate 6. This leads to cancellation due to interference, so that the illuminated area becomes smaller compared to the point-like focusing mode. Illumination with the evanescent light L3 in the annular focusing mode is subsequently referred to as point illumination. (a) and (b) in Fig. Figure 4 shows a comparison of the illuminated areas in plane lighting and point lighting. (a) in Fig. 4 shows an illumination region R1 by plane illumination and (b) in Fig. Figure 4 shows an illumination region R2 by point illumination. In the case of plane illumination in (a) in Fig. In step 4, a large region of object 8 is illuminated all at once with the evanescent light L3. The spatial resolution is approximately several micrometers. In contrast, with the point illumination in (b) Fig. 4a Since the region illuminated at once with the evanescent light L3 is smaller compared to the plane illumination, the influence of spot noise is reduced and a spatial resolution of up to several hundred nanometers is achieved. Depending on the state of the object 8, based on, for example, an input from the input unit 42, one of the plane illumination (i.e., the point-like focusing mode) and the point illumination (i.e., the ring-shaped focusing mode) is selected.

[0018] Fig. Figure 5 shows a Fresnel lens pattern P2 for plane illumination as an example of the Fresnel lens pattern P1. Fig. The phase values ​​are represented by color shades in section 5. In the section on... Fig. In the Fresnel lens pattern P2 shown in Figure 5, the illumination light L2 has the focusing point F1, for example, at the position on the pupil plane 9, which is shown in (b). Fig. 2 is shown. (a) and (b) in Fig. Figure 6 shows a total internal reflection mode of the illumination light L2 in the plane illumination. (a) in Fig. Figure 6 shows that the illumination light L2 is shaped into parallel light by the objective lens after being focused at the pupil plane 9 and then enters the object substrate 6. (b) in Fig. Figure 6 shows the pupil plane 9 from the direction of the optical axis of the illumination light L2, as well as the region 9A, which is contained in the pupil plane 9.

[0019] The angle of incidence θ of the illuminating light L2 is determined by formula (2) using a distance D. NA expressed on the pupil plane 9 from an optical axis L0 of the objective lens 5 to an optical path of the illumination light L2. [Formula 2] θ=sin−1(DNA / n1)

[0020] Here, n1 represents a refractive index of the glass, of which the object substrate 6 is made, and the immersion oil 7. From equation (2) it follows that the illumination light L2 undergoes total internal reflection by the object substrate 6 when the illumination light L2 is focused to a point shape on the pupil plane 9 in a region of the value D NA The light is concentrated by the angle of incidence θ and a critical angle θ. c fulfill a relationship defined by θ > θ cis expressed. Formula (2) also shows that if the position of the focusing point F1 changes, the angle of incidence θ also changes accordingly. As described above, the illumination L2 undergoes total internal reflection when the focusing point F1 is located in region 9A, which is indicated by the dashed lines in the pupil plane 9 in (b) in Fig. 6 is indicated.

[0021] The critical angle θ c is as expressed by formula (3). [Formula 3] θc=sin−1(n2 / n1)

[0022] Here, n2 is a refractive index of a region that is in contact with the object mounting surface 6b and is located outside the object substrate 6.

[0023] If the position of the focusing point F1 changes during the illumination of the plane, not only does the angle of incidence θ of the illumination light L2 on the object substrate 6 change, but also a polarization state of the illumination light L2 as it enters the object substrate 6. (a) and (b) in Fig. Figure 6 shows the principle of the polarization process of the illumination light L2. (a) in Fig. Figure 7 shows a plane of incidence of the illumination light L2 on the object substrate 6. In (a) in Fig. 7 is a plane OTSN, a reference plane Q1 perpendicular to the pupil plane 9, and a plane OLMN is an incident plane Q2 of the illumination light L2. The reference plane Q1 and the incident plane Q2 form an angle α. The illumination light L2 passes through the incident plane Q2 and enters the object substrate 6 at the angle of incidence θ. (b) in Fig. Figure 7 describes a polarization state of the illumination light L2 and illustrates a frequency space of the pupil plane 9 with the axes µ-ξ. The reference plane Q1 includes the µ-axis and is perpendicular to a µ-ξ plane. It is assumed that the focusing point F1 lies on a line of the segment OL, as in (b) from Fig. 7 shown.

[0024] If the illumination light L2, for example, has an amplitude E in the µ-axis direction i If the light is linearly polarized, the polarization state of the illumination light L2 upon entering the object substrate 6 is expressed by formulas (4) to (6). [Formula 4] Ep=Ei cos α [Formula 5] Es=Ei sin α [Formula 6] α=tan−1(ξμ)

[0025] The values ​​Ep and Es represent the amplitudes of a P-polarized component and an S-polarized component of the illumination light L2, respectively. Equations (4) to (6) show that the values ​​Ep and Es are uniquely determined in relation to the angle α, and that if the angular position of the focusing point F1 on the pupil plane 9 changes, the polarization state of the illumination light L2 also changes. That is, the polarization state of the illumination light L2 that yields the evanescent light L3 suitable for a given state of the object 8 can be achieved by adjusting the position of the focusing point F1 on the pupil plane 9.

[0026] Fig. Figure 8 is a visualization of a relationship between the angle α on the pupil plane 9 and a polarization plane of the illumination light L2. In Fig. Figure 8 represents the ratio of the P-polarization to the S-polarization of the illumination light L2, represented by the color shading in region 9A on the pupil plane 9. A region 9B, shown as black within region 9A, represents a region where the illumination light L2 does not undergo total internal reflection but is transmitted. If the shading in Fig. When region 8 in 9A becomes brighter, the proportion of the P-polarized component increases, while the proportion of the S-polarized component decreases. Conversely, when the shading in region 9A becomes darker, the proportion of the P-polarized component decreases, while the proportion of the S-polarized component increases.

[0027] Based on Fig. Figure 8 shows that if the focusing point F1 is located on the µ-axis, the illuminating light L2 exhibits only P-polarization, and if the focusing point F1 is located on the ξ-axis, the illuminating light L2 exhibits only S-polarization. It also becomes clear that if the focusing point F1 is located at a position other than the µ- or ξ-axis, the illuminating light L2 exhibits both P- and S-polarization.

[0028] The setting of the position of the focusing point F1 on the pupil plane 9 is preferably carried out in the spatial light modulator 4 by an electronic command from the processing unit 41, through which the illumination light L1 is focused into a point shape at the position. Alternatively, a plurality of Fresnel lens patterns P1 corresponding to a plurality of polarization states are preferably prepared in advance, and the pattern that produces a desired polarization state is selected from the pre-prepared Fresnel lens patterns P1. The selected pattern is then displayed on the spatial light modulator 4 by the electronic command from the processing unit 41.

[0029] The light intensity (electric field strength) of the evanescent light L3, which is generated on the object mounting surface 6b of the object substrate 6, varies depending on the angle of incidence θ and the polarization state. The light intensity It(0) of the evanescent light L3 on the object mounting surface 6b of the object substrate 6 is the sum of a light intensity I P (0) of the P-polarized component and a light intensity I S (0) of the S-polarized component, as expressed by formula (7). [Formula 7] It(0)=Ip(0)+Is(0)

[0030] The light intensity I can be adjusted P (0) of the P-polarized component and the light intensity I S (0) of the S-polarized component of the evanescent light L3 in formula (7) can be expressed by formulas (8) and (9). [Formula 8] Ip(0)=Ipx+Ipz [Formula 9] Is(0)=Ipy

[0031] It should be noted that the light intensities I px , I py and I pz of the evanescent light L3 can be obtained from the following formulas (10) to (12). [Formula 10] Ipx=|Ep|2{4 cos2 θ(sin2θ−n2n4cos2θ+sin2θ−n2} [Formula 11] Ipz=|Ep|2{4 cos2θ sin2θn4 cos2θ+sin2θ−n2} [Formula 12] Ipy=|Es|2{4 cos2θ1−n2}

[0032] Here, θ represents the angle of incidence of the illumination light L2 on the object substrate 6 and n represents a refractive index ratio of n1 and n2, as expressed in formula (13). [Formula 13] n=n2n1

[0033] The light intensity of the evanescent light L3 can be expressed by a function It(z) of a distance z from the object mounting surface 6b of the object substrate 6, so that the penetration length d of the evanescent light L3 can be calculated from the function It(z) of the distance z. The light intensity It(z) of the evanescent light L3 is expressed by formula (14). [Formula 14] I(z)=I(0)e−z / d

[0034] The value It(0) represents the light intensity of the evanescent light L3 on the object mounting surface 6b of the object substrate 6. The penetration length d of the evanescent light L3 is obtained using formula (15). [Formula 15] d=λ04π(n12sin2θ−n22)−1 / 2

[0035] (a) to (d) in Fig. Figure 9 shows a relationship between the light intensity It and a penetration length d of the evanescent light L3 and a position of the focusing point F1 on the pupil plane. It should be noted that a relationship expressed by formula (16) is assumed for the calculation of the light intensity It of the evanescent light L3. [Formula 16] |Ep|2+|Es|2=1

[0036] The luminous intensity It of the evanescent light L3 is calculated as the square of the intensity, as expressed in formula (17). In formula (17), the value It(z) is represented by It. [Formula 17] It2=(Ipx+Ipy+Ipz)2

[0037] (a) in Fig. 9 is a calculation result of a relationship between a position of the focusing point F1 on the pupil plane 9 and a square value according to 2the light intensity on the object mounting surface 6b. In the drawing, a circular black region D in the center of region 9B corresponds to the pupil plane 9, in which the illumination L2 is not subject to total internal reflection but is transmitted. The positions on the pupil plane 9 corresponding to the dashed lines A and B represent the polarization states of only P-polarization and only S-polarization, respectively. The state of exclusive P-polarization (dashed line A) is shown brighter than that of exclusive S-polarization (dashed line B), which shows that the square value according to 2 the light intensity is high.

[0038] (am Fig. 9 is a calculation result of the dependence of the value of the numerical aperture (NA) on the square value according to 2 the light intensity. In (b) in Fig. 9 is the size of the square value according to 2The light intensity is normalized on the vertical axis and expressed in an arbitrary unit. Furthermore, in (b) in Fig. 9 represents the distance between the center of the pupil plane 9 and the focusing point F1, represented by the NA value. If, in the figure, the angle of incidence θ equals the critical angle θ c If the angle of incidence θ is 1.0, then the NA value is 1.0, and if the angle of incidence θ is the critical angle θ c If the NA value exceeds 1.0, both the luminous intensity It of dashed line A and the luminous intensity It of dashed line B have a similar tendency, and when the NA value is larger, that is, when the angle of incidence θ is greater than the critical angle θ c The larger the value, the squared value increases according to the formula. 2 The light intensity decreases monotonically. Conversely, it is shown that the light intensity It on the object mounting surface 6b increases when the angle of incidence θ is closer to the critical angle θ. clies. Furthermore, (a) is in Fig. 9 the square value according to 2 The light intensity for dashed line A is greater than that for dashed line B.

[0039] It should be noted that, depending on the state of object 8, the light intensity It is preferably not necessarily the maximum value, in which case changing the NA value to a preferred value results in the desired light intensity It. Changing the NA value is accomplished by altering the distance between a position of the focusing point F1 on the pupil plane 1 and a midpoint of the pupil plane.

[0040] (c) in Fig. Figure 9 is a calculated result of a relationship between the position of the focusing point F1 on the pupil plane 9 and the penetration length d of the evanescent light L3. In the figure, the penetration length d is defined as a length at which the light intensity of the evanescent light L3 is equal to lt. 2 multiplied by e -2 is, whereby according to 2 The square of the light intensity on the object mounting surface 6b is given. In this figure, the penetration length d of the P-polarization is calculated as a length in which the light intensity of the P-polarization is equal to lt. 2 multiplied by e -2 is, and the penetration length d of the S-polarization is also calculated as a length in which a light intensity of the S-polarization is equal to lt 2 multiplied by e -2Therefore, a difference in the polarization states of the P-polarization and the S-polarization does not lead to a difference in the shading of region 9A. Both the P-polarization and the S-polarization are shown as uniformly bright near the outer edge of region 9B.

[0041] (d) in Fig. Equation 9 is a calculation result showing the dependence of the NA value on the penetration length d. Furthermore, in (d) in Fig. 9 the penetration length d is defined as a length in which the light intensity of the evanescent light L3 is equal to lt 2 multiplied by e -2 is, whereby according to 2 the square of the light intensity on the object mounting surface 6b is. (d) in Fig. 9 is a calculation result for a dashed line C on the pupil plane 9, with the unit nm for the penetration length d. Similar to the case of light intensity It in (b) in Fig. 9, if the NA value is larger, that is, if the angle of incidence θ is larger than the critical angle θ c As the angle of incidence θ approaches the critical angle θ, the penetration length d decreases monotonically. Conversely, it is shown that the penetration length d increases when the angle of incidence θ approaches the critical angle θ. c lies.

[0042] It should be noted that, similarly to the case of light intensity It from (b) in Fig. 9, depending on the state of the object 8, preferably not the maximum value for the penetration length d is chosen, in which case changing the NA value to a preferred value leads to the desired penetration length d. As in the case of changing the light intensity It, the change of the NA value is carried out by changing the distance between a position of the focusing point F1 on the pupil plane 9 and the center position of the pupil plane 9.

[0043] If the illumination light L2 forms the focusing point F1 in a point form on the pupil plane 9, plane illumination is performed, and if furthermore a plurality of focusing points F1 are present on the pupil plane 9, plane illumination is performed in a different mode than the plane illumination described above. Fig. Figure 10 shows a configuration with two focusing points F1a and F1b at the pupil level. Figure 9 (a) in Fig. Figure 10 shows a configuration of the lighting device 1 for total internal reflection of light from Fig. 1, and (b) in Fig. Figure 10 shows the pupil plane 9 from the direction of the optical axis of the illumination light L2, with a region 9A contained in the pupil plane 9.

[0044] Fig. Figure 11 is a representation of a Fresnel lens pattern P3 for providing two focusing points F1a and F1b on the pupil plane 9. In the configuration of the illumination device 1 for total internal reflection of light shown in (a) in Fig. As shown in Figure 10, the presentation of the Fresnel lens pattern P3 in Fig. 11, for example, to two focusing points F1a and F1b in region 9A of the pupil plane 9. When this Fresnel lens pattern B3 is presented, the illumination light components L2a and L2b passing through the focusing points F1a and F1b, respectively, generate propagation light components that spread in opposite directions to each other on the object substrate 6. Therefore, the two propagation light components interfere with each other, thereby generating interference fringes, and the interference fringes are also generated in the evanescent light L3 that illuminates the object 8.

[0045] (a) and (b) in Fig. Figure 12 shows the observation results of interference fringes when two focusing points F1a and F1b are present at the pupil plane 9. (a) in Fig. Figure 12 shows an observation result when the angle of incidence θ of the illumination light L2 on the object substrate 6 is 7.5°, and (b) in Fig. Figure 12 shows an observation result when the angle of incidence θ is 13.0°. The comparison between (a) in Fig. 12 and (b) Fig. Figure 12 shows that a shorter interval between the two focusing points F1a and F1b leads to a wider interval of interference fringes. (a) and (b) in Fig. Figure 12 shows that a change in the angle of incidence 9 of the illumination light L2, i.e. a change in the interval between the two focusing points F1, allows the arbitrary setting of an interval between the interference fringes.

[0046] (a) to (c) in Fig. Figure 13 shows the observation results of interference fringes of evanescent light L3 when eight focusing points are present on the pupil plane 9. With plane illumination, eight focusing points F1c to F1j can be formed on a µ-ξ plane of the pupil plane 9. (a) in Fig. Figure 13 shows the eight focusing points F1c to F1j at the pupil plane. 9. (b) in Fig. Figure 13 conceptually shows how propagation light components W1c to W1j of illumination light components, each passing through the focusing points F1c to F1j, interfere with each other and thereby produce interference fringes. (c) in Fig. Figure 13 shows the interference fringes of the evanescent light, which are produced by the interference of the propagation light components W1c to W1j. In (c) in Fig. Figure 13 is part G1, shown brightly in white, a region of constructive interference, whereas part G2, shown darkly in black, is a region of destructive interference. Even with eight focusing points, changing the angle of incidence θ of the illumination L2 allows for arbitrary adjustment of the interval between the interference fringes.

[0047] Fig. Figure 14 shows an observation of illumination light L2 passing through the object substrate 6 when the angle of incidence θ of the illumination light L2 is zero degrees. When the angle of incidence θ of the illumination light L2 is zero degrees, the illumination light L2 does not undergo total internal reflection but passes through the object substrate 6 as is. Therefore, there is no illumination of the object 8 with the evanescent light L3. Since the number of focusing points F1 is one, no interference fringes are observed.

[0048] Fig. Figure 15 shows, as an example of the lens pattern P1 for point illumination in an annular focusing mode, a lens pattern P4 in which a toroidal Fresnel lens pattern is superimposed with a pattern for correcting distortion by an optical system. For example, in the toroidal Fresnel lens pattern P4, in the configuration of the illumination device 1 for total internal reflection of light shown in (a) in Fig. As shown in 3 and described above, the illumination light L2 is focused into a ring shape on the pupil plane 9, as in (b) in Fig. Figure 3 shows the focusing ring F2. Furthermore, in point illumination where the focusing mode is ring-shaped, the illumination light L2 undergoes total internal reflection on the object substrate 6 if the angle of incidence θ of the illumination light L2 on the object substrate 6 has a relationship of θ > θ c relative to the critical angle θ cfulfilled. One illumination mode of the evanescent light L3 for object 8 is point-like with a small illumination area, as described above.

[0049] (a) and (b) in Fig. Figure 16 shows observation results of spot illumination in the ring-shaped focusing mode. (a) in Fig. Figure 16 shows an observation result of the evanescent light L3 and (b) in Fig. Figure 16 shows the focusing ring F2 of the pupil plane 9. On the pupil plane 9, the focusing ring F2 is formed in region 9A when the angle of incidence θ of the illumination light L2 has a relationship of θ > θ c relative to the critical angle θ c fulfilled. As in (a) in Fig. Figure 16 shows that the observation reveals that the illumination by the evanescent light L3 is a point illumination with a small illumination area.

[0050] In point illumination using the ring-shaped focusing mode, a change in the radius size of the focusing ring F2 leads to the desired penetration length d or light intensity It of the evanescent light L3. Fig. Figure 17 shows a NA value dependence of the light intensity It of the evanescent light L3. Fig. 17 is the magnitude of the light intensity It normalized on the vertical axis and expressed in any unit.

[0051] Similar to the case of plane illumination, when the NA value is larger, i.e., when the angle of incidence θ of the illumination light L2 is greater than the critical angle θ c As the angle of incidence increases, the light intensity lt decreases monotonically. Conversely, it is shown that the light intensity lt on the object mounting surface 6b increases when the angle of incidence θ is closer to the critical angle θ. cThis means that the light intensity lt of the evanescent light L3 increases when a radius of the focusing ring F2 gradually decreases towards a region adjacent to the critical angle θ. c This corresponds to the following: The penetration length d increases as the radius of the bundling ring F2 gradually decreases in the direction of the region corresponding to the critical angle θ. c corresponds.

[0052] This means that the larger the radius of the focusing ring F2, the lower the light intensity It of the evanescent light L3, and consequently the penetration length d becomes shorter. Conversely, the smaller the radius of the focusing ring F2, the greater the light intensity It of the evanescent light L3, and consequently the penetration length d becomes longer. Depending on the condition of the object 8, the maximum value for the light intensity It of the evanescent light L3 is preferably not chosen, and in this case, changing the radius of the focusing ring F2 allows a change in the NA value so that the desired light intensity It or penetration length d can be achieved.

[0053] It should be noted that there are means other than presenting the toroidal Fresnel lens pattern P4 on the spatial light modulator 4 for focusing the illumination light L2 into a ring shape, such as providing a mask on the spatial light modulator 4 in such a way that the illumination light L2 is focused into a ring shape. Furthermore, it is possible to refract the illumination light L2 through the spatial light modulator 4 in such a way that the illumination light L2 is focused into a ring shape.

[0054] (a) to (f) in Fig. Figure 18 shows the beam shape of the evanescent light L3 during point illumination in the ring-shaped focusing mode. (a) in Fig. Figure 18 shows the toroidal Fresnel lens pattern P4 in Fig. 15, and (b) and (c) in Fig. Figure 18 shows the observation results of the evanescent light L3 when the toroidal Fresnel lens pattern P4 in (a) in Fig. 18 is used. (d) in Fig. Figure 18 shows a toroidal Fresnel lens pattern P5 of a variation of (a) in Fig. 18. (e) and (f) in Fig. Figure 18 shows observation results of the evanescent light L3 when the toroidal Fresnel lens pattern P5 in (d) is from Fig. 18 is used.

[0055] (b) and (e) from Fig. Figures 18 show observation results of the evanescent light L3 when the NA value is between 1.05 and 1.06. (c) and (f) in Fig. Figure 18 shows observation results of the evanescent light L3 when the NA value is between 1.35 and 1.36. With point illumination in the ring-shaped focusing mode, careful observation allows the observation of a multitude of rays other than the evanescent light L3. Thus, in (b) and (c) Fig. 18 two light focusing points were observed, whereas in (e) and (f) Fig. 18 Three light focusing points can be observed.

[0056] In (b) and (c) from Fig. 18. A twisted beam shape of the evanescent light L3 with a left-right asymmetry can be observed. The photoelectric field distribution of the evanescent light L3 depends on the polarization direction of the illumination light L2 incident on the object substrate 6. For example, if the illumination light L2 has a linear polarization, one shape of the photoelectric field distribution of the evanescent light L3 is extended in the direction of the polarization direction of the illumination light L2. When the evanescent light L3, with its beam shape extended in the polarization direction of the illumination light L2, illuminates the object 8, the observed image of the object 8 is projected with an extension in the direction of the polarization direction of the illumination light L2.

[0057] When the illumination light L2 is used with a left-right symmetrical polarization state, the distortion of the point shape of the evanescent light L3 is reduced. This is shown in the toroidal Fresnel lens pattern P5 in (b). Fig. 18 will be half a region of the pattern from (a) in Fig. 18 with a pattern phase-shifted by π (rad) is added. Thus, the illumination light L2 is generated with a left-right symmetrical polarization state, so that the point shapes of the evanescent light L3 in (e) and (f) are derived from Fig. 18 compared to (b) or (c) from Fig. 18 will be adjusted.

[0058] In this way, the point illumination in the ring-shaped focusing mode, in which the toroidal Fresnel lens pattern P5 is used, which generates the illumination light L2 with a left-right symmetrical polarization state, leads to a reduction in the distortion in the photoelectric field distribution of the evanescent light L3 and an improved point shape. Furthermore, it follows from (b) and (c) Fig. 18 and (e) and (f) from Fig. 18 shows that the larger NA value leads to a smaller interval between the points of evanescent light L3.

[0059] Fig.Figure 19 shows the determination processes for the Fresnel lens pattern for plane illumination and point illumination. In the total internal reflection illumination device 1, the processing unit 41 calculates a Fresnel lens pattern, provides feedback according to the desired illumination conditions for both plane and point illumination, and determines a phase pattern. A Fresnel lens pattern based on the determined phase pattern is presented to the spatial light modulator 4 by electronic command from the processing unit 41.

[0060] In plane illumination, the phase pattern is determined such that the illumination light L2 is focused into a point shape on the pupil plane 9. Furthermore, the desired light intensity It or penetration length d of the evanescent light L3 is set according to a state of the object 8, such as its thickness, concentration, and the like. Additionally, a ratio of the P-polarization to the S-polarization of the evanescent light L3 is set according to the polarization dependence of the object 8 (step S11). Based on the defined illumination conditions, the computation unit 41 calculates the Fresnel lens pattern (step S12) through optimization calculation feedback for the phase pattern and the illumination conditions (step S1).The phase pattern is determined after the calculation step (step S2), and then the Fresnel lens pattern is presented on the spatial light modulator 4 based on the phase pattern determined by the calculation unit 41.

[0061] For point illumination, the phase pattern is determined such that the illumination light L2 is focused into a ring shape at the pupil plane 9. Furthermore, the desired light intensity lt, penetration length d, or a shape of the evanescent light L3 is set according to the state of the object 8, such as thickness, concentration, and the like (step S21). Based on the defined illumination conditions, the computation unit 41 calculates the toroidal Fresnel lens pattern (step S22) using the optimization calculation feedback for the phase pattern and the illumination conditions (step S1). The phase pattern is determined after the calculation step (step S2), and subsequently, the toroidal Fresnel lens pattern, based on the phase pattern determined by the computation unit 41, is presented on the spatial light modulator 4.

[0062] The following describes the effects achieved by the total internal reflection illumination device 1 of the present embodiment. As described above, in the total internal reflection illumination device 1 for illuminating the object 8 with the evanescent light L3, when the illumination light L2 is focused on the pupil plane 9 of the objective lens 5, a change in the focusing shape or focusing position leads to a significant change in the polarization state, the penetration length, the shape, or the light intensity of the evanescent light L3. Furthermore, in this total internal reflection illumination device 1, an electronic command from the processing unit 41 causes the Fresnel lens pattern P1 to be displayed on the spatial light modulator 4, so that the focusing shape or focusing position on the pupil plane 9 of the objective lens 5 can be easily changed.

[0063] Thus, for example, evanescent light L3 with the desired polarization can be obtained from a P-polarization and an S-polarization according to the polarization dependence of the object 8. Furthermore, the evanescent light L3 with the desired penetration length, shape, or light intensity can be obtained according to a state of the object 8, such as thickness, concentration, or the like. In this way, the total internal reflection illumination device 1 allows for easy adjustment of the polarization state, penetration length, shape, and light intensity of the evanescent light L3 with a simple configuration.

[0064] Furthermore, in the lighting device 1 for total reflection of light of the present embodiment, the calculation unit 41 can generate the Fresnel lens pattern P1 according to the desired polarization state of the evanescent light L3 and provide it for the spatial light modulator 4.

[0065] In this case, the Fresnel lens pattern B1, which modifies a focusing shape or focusing position on the pupil plane 9 of the objective lens 5, is generated on the spatial light modulator 4 by an electronic command from the processing unit 41. Thus, for example, the evanescent light L3 with the desired polarization can be obtained from a P-polarization and an S-polarization according to the polarization dependence of the object 8. Furthermore, the evanescent light L3 can be obtained with the desired penetration length, shape, or light intensity according to a state of the object 8, such as thickness, concentration, or the like.

[0066] Furthermore, in the lighting device 1 for total reflection of light of the present embodiment, the calculation unit 41 can select a Fresnel lens pattern P1 according to the desired polarization state of the evanescent light L3 from a plurality of Fresnel lens patterns P1, which were prepared in advance according to a polarization state of the evanescent light L3, and provide it for the spatial light modulator 4.

[0067] In this case, a multitude of Fresnel lens patterns B1, each corresponding to a polarization state of the evanescent light L3, are pre-prepared. From these pre-prepared Fresnel lens patterns B1, a desired pattern is selected by electronic command from the processing unit 41. For example, the Fresnel lens pattern P1 that produces evanescent light L3 with the desired polarization from the P-polarization and the S-polarization is selected according to the polarization dependence of the object 8. Furthermore, the Fresnel lens pattern P1 that produces evanescent light L3 with the desired penetration length, shape, or light intensity is selected according to the state of the object 8, such as thickness, concentration, or the like.

[0068] Furthermore, the Fresnel lens pattern P1 can be a pattern that allows the plane of incidence Q2 to form an angle α with the optical axis of the illuminating light L2 incident on the object surface 8 and the reference plane Q1, which is perpendicular to the pupil plane 9, corresponding to the desired polarization state of the evanescent light L3. The angle α formed by the plane of incidence Q2 with the optical axis of the illuminating light L2 incident on the object surface and the reference plane Q1, which is perpendicular to the pupil plane 9, uniquely corresponds to a polarization state of the illuminating light L2. Thus, the polarized components of the evanescent light L3 can be easily adjusted by changing the angle α.

[0069] Furthermore, in the illumination device 1 for total internal reflection of light of the present embodiment, the Fresnel lens pattern P1 can be a pattern in which a distance between a focusing position of the illumination light L2 on the pupil plane 9 and a midpoint of the pupil plane 9 corresponds to the desired penetration length or the desired light intensity of the evanescent light L3. Changing the distance between the focusing position of the illumination light L2 on the pupil plane 9 and the midpoint of the pupil plane leads to a change in the relationship between the angle of incidence θ of the illumination light L2 and the critical angle θ c During total internal reflection of the illumination light L2, the relationship between the angle of incidence θ of the illumination light L2 and the critical angle θ is given. crefers to the penetration length and light intensity of the evanescent light L3. Thus, by changing the distance between the focusing position of the illumination light L2 on the pupil plane 9 and the center position of the pupil plane 9, the desired penetration length and light intensity of the evanescent light L3 can be easily achieved.

[0070] Furthermore, in the total internal reflection lighting device 1 of the present embodiment, the Fresnel lens pattern P1 can be a pattern in which the illumination light L2 can be focused into a point shape on the pupil plane 9. The evanescent light L3 produced by this Fresnel lens pattern P1 can illuminate a larger area of ​​the object 8 compared to the ring-shaped focusing mode.

[0071] Furthermore, in the total internal reflection lighting device 1 of the present embodiment, the Fresnel lens pattern P1 can be a pattern in which the illumination light L2 can be focused into a ring shape on the pupil plane 9. The evanescent light L3 produced by this Fresnel lens pattern P1 illuminates the object 8 in a point-like manner and can thus illuminate a tiny area in a concentrated way.

[0072] Furthermore, the total internal reflection lighting device 1 of the present embodiment allows the selection of either a point shape or a ring shape as the mode for focusing the illumination light L2 onto the pupil plane 9. Thus, the operator can freely change the illumination area for the object 8.

[0073] The illumination device for total internal reflection of light according to the present invention has been described in detail above. However, the illumination device for total internal reflection of light according to the present invention is not limited to the embodiments described above, but can include numerous further modifications. For example, the device can be used not only in a total internal reflection microscope, but also, for example, in surface treatment using evanescent light. Since the penetration length or light intensity of the evanescent light can be adjusted, a surface can be prepared with a preferred level of accuracy.

[0074] Furthermore, the object was described as object 8, which is placed on the object mounting surface 6b. However, evanescent light can also be generated within the object by subjecting the illumination light to total internal reflection on a surface of the object. For example, in a semiconductor device such as an integrated semiconductor circuit, the substrate of the semiconductor device acts as the object substrate, thus enabling evanescent light to be generated near the substrate of the semiconductor device to illuminate a device surface (corresponding to object 8) of the semiconductor device.

[0075] Furthermore, the liquid immersion lens method was described, in which immersion oil 7 is arranged between the objective lens 5 and the objective substrate 6; however, a solid immersion lens with a refractive index equal to that of the object substrate 6 can also be arranged on the object substrate 6. This is effective when the use of liquid is difficult with objects such as a semiconductor device.

[0076] The total internal reflection lighting device according to the present embodiment generates evanescent light by illuminating an object with light, and the total internal reflection lighting device comprises a light source for providing illumination; a spatial light modulator for inputting the illumination, and for focusing and outputting the illumination by receiving the input of the illumination and presenting a lens pattern; an objective lens for illuminating the object with the light by illuminating an object surface with the illumination light, which is focused and output by the spatial light modulator, and for generating total internal reflection thereby;and a computing unit for providing the lens pattern according to a desired polarization state of the evanescent light to the spatial light modulator, wherein the lens pattern is a pattern which focuses the illumination light onto a pupil plane of the objective lens.

[0077] Furthermore, in the total internal reflection lighting device, the calculation unit can generate the lens pattern according to the desired polarization state of the evanescent light and provide it for the spatial light modulator.

[0078] In this total internal reflection illumination device, the lens pattern, which changes the focusing shape or position at the pupil plane of the objective lens, is generated on the spatial light modulator by an electronic command from the processing unit. Thus, for example, evanescent light with the desired polarization can be achieved from P-polarization and S-polarization according to the polarization dependence of the object. Furthermore, evanescent light with a desired penetration length, shape, or light intensity can be achieved according to a property of the object such as thickness, concentration, and the like.

[0079] Furthermore, in the total internal reflection lighting device, the computing unit can select a lens pattern according to the desired polarization state of the evanescent light from a multitude of lens patterns that have been pre-prepared according to a polarization state of the evanescent light, and provide it for the spatial light modulator.

[0080] In this total internal reflection illumination device, a multitude of lens patterns, each corresponding to a polarization state of evanescent light, are pre-prepared. From these pre-prepared lens patterns, the desired pattern is selected by the processing unit via electronic command. For example, the lens pattern that produces evanescent light with the desired polarization (P-polarization and S-polarization) is selected according to the polarization dependence of the object. Furthermore, the lens pattern that produces evanescent light with the desired penetration length, shape, or light intensity is selected according to the object's properties, such as thickness, concentration, and the like.

[0081] Furthermore, the lens pattern can be configured as a pattern which allows the plane of incidence to form an angle with the optical axis of the illumination light incident on the object surface and the reference plane, which is perpendicular to the pupil plane, corresponding to the desired polarization state of the evanescent light.

[0082] According to the knowledge of the presenting inventors, the angle formed by the plane of incidence, which contains the optical axis of the illumination light incident on the object surface, and the reference plane, which is perpendicular to the pupil plane, uniquely corresponds to a polarization state of the illumination light. Thus, polarized components of the evanescent light can be easily adjusted by changing the angle.

[0083] Furthermore, the illumination device for total internal reflection of light of the present embodiment can be configured such that the lens pattern is a pattern in which a distance between a focusing position of the illumination light on the pupil plane and a center position of the pupil plane corresponds to the desired penetration length or the desired light intensity of the evanescent light.

[0084] Changing the distance between the focusing point of the illumination light on the pupil plane and the midpoint of the pupil plane alters the relationship between the angle of incidence of the illumination light and the critical angle for total internal reflection. This relationship relates to the penetration length and intensity of the evanescent light. Therefore, by changing the distance between the focusing point of the illumination light on the pupil plane and the midpoint of the pupil plane, the desired penetration length and intensity of the evanescent light can be easily achieved.

[0085] Furthermore, the total internal reflection lighting device can be configured such that the lens pattern is one that focuses the illumination light into a point shape at the pupil plane. The evanescent light formed by this lens pattern can illuminate a larger area of ​​the object compared to the ring-shaped focusing mode described later.

[0086] Furthermore, the illumination device for total internal reflection can be configured such that the lens pattern is one that focuses the illumination light into a ring shape at the pupil plane. The evanescent light produced by this lens pattern illuminates the object as a point source, thus illuminating a tiny area in a concentrated manner.

[0087] Furthermore, the total internal reflection lighting device can be configured to select either a point or ring shape as the mode for focusing the illumination light onto the pupil plane 9. This allows the operator to freely change the illuminated area of ​​the object. Commercial applicability

[0088] The present invention can be used as a total internal reflection lighting device, by means of which a polarization state, penetration length, shape and light intensity of evanescent light can be adjusted with a simple configuration. Reference symbol list

[0089] 1 - Lighting device for total internal reflection of light, 2 - Light source, 3 - Focusing lens, 4 - Spatial light modulator, 5 - Objective lens, 6 - Object substrate, 7 - Immersion oil, 8 - Object, 9 - Pupil plane, 41 - Calculation unit, L1, L2 - Illuminating light, L3 - Evanescent light, F1 - Focusing point, F2 - Focusing ring, P1 - Lens pattern.

Claims

[1] Lighting device for total internal reflection of light for generating evanescent light (L3) by illuminating an object (8) with light (L2), wherein the lighting device for total internal reflection of light (1) comprises: a light source (2) for providing illumination light (L1); a spatial light modulator (4) for inputting the illumination light (L1), and for modulating the illumination light (L1) by means of a lens pattern (P1); an objective lens (5) for illuminating an object surface with the modulated illumination light (L2) and thereby generating total internal reflection; and a computation unit (41) for providing the lens pattern (P1) according to a desired polarization state of the evanescent light (L3) to the spatial light modulator (4), wherein The lens pattern (P1) provided by the computation unit (41) is a pattern for focusing the illumination light (L2) at a position on a pupil plane of the objective lens (5) according to the desired polarization state of the evanescent light (L3). [2] Lighting device for total reflection of light according to claim 1, wherein the computation unit (41) generates the lens pattern (P1) according to the desired polarization state of the evanescent light (L3). [3] Lighting device for total internal reflection of light according to claim 1, wherein the computation unit (41) selects a lens pattern (P1) based on the desired polarization state of the evanescent light (L3) from a plurality of lens patterns (P1) that have been pre-prepared and correspond to a polarization state of the evanescent light (L3). [4] Lighting device for total internal reflection of light according to one of claims 1 to 3, wherein the lens pattern (P1) is a pattern which makes it possible for an incident plane with an optical axis of the illumination light (L2) incident on the object surface and a reference plane perpendicular to the pupil plane (9) to form an angle corresponding to the desired polarization state of the evanescent light (L3). [5] Lighting device for total internal reflection of light according to any one of claims 1 to 4, wherein the lens pattern (P1) is a pattern which makes it possible to focus the illumination light (L2) into a point shape on the pupil plane (9). [6] Lighting device for total internal reflection of light according to any one of claims 1 to 4, wherein the lens pattern (P1) is a pattern in which the illumination light (L2) can be focused into a ring shape on the pupil plane (9). [7] Lighting device for total internal reflection of light according to one of claims 1 to 4, wherein the mode for focusing the illumination light (L2) on the pupil plane (9) is a point shape or a ring shape.

Images