Optical apparatus and illumination method

Abstract

The present invention provides an optical device and illumination method that can more effectively improve the uniformity of illumination light. [Solution] The optical device 1 according to this embodiment includes a light source 10 that generates illumination light L1, an integrator optical element 20 that homogenizes the illumination light L1, a focusing element 46 that focuses the illumination light L1 to illuminate the target object 60, a deflection element 30 that is positioned after the integrator optical element 20 and before the focusing element 46 as seen from the light source 10, and is positioned conjugate to the illumination surface 61 of the target object 60, and a drive unit 50 that drives the deflection element 30 to change the direction of the illumination light L1 emitted from the deflection element 30.

Description

Technical Field

[0001] The present disclosure relates to an optical device and a lighting method.

Background Art

[0002] In optical devices such as inspection devices, projectors, and exposure devices, lighting devices using laser light sources are used. When illuminating an observation portion or the like, it is desirable to perform surface illumination with a uniform light intensity distribution. Therefore, even when using a laser light source, it is required to perform uniform illumination.

[0003] As a technology related to this, the laser light source of Patent Document 1 can be cited. As a first example, the laser light source of Patent Document 1 arranges a galvanometer mirror above a diffraction grating and an angular rod, and reflects the laser light from the laser light source toward the diffraction grating by the galvanometer mirror. Then, by changing the posture of the galvanometer mirror, the incident position of the laser light on the diffraction grating is changed. Thereby, the laser light source of Patent Document 1 equalizes the laser light used as illumination light. Further, as a second example, the laser light source of Patent Document 1 equalizes the laser light used as illumination light by making the laser light diffracted by a reflective or transmissive diffraction grating incident on the angular rod.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration of the first example in Patent Document 1, the irradiation position on the sample may fluctuate frequently because the incident position on the diffraction grating changes. Also, in the configuration of the second example in Patent Document 1, a bias in the intensity distribution corresponding to the number of times light is reflected within the square rod may appear discretely in a grid pattern. Such a grid-like distribution may also appear when a fly-eye lens is used instead of the square rod. Thus, the laser light source in Patent Document 1 has room for improvement in order to perform stable observation and other operations.

[0006] This disclosure has been made in view of these problems and provides an optical device and illumination method that more preferably improve the uniformity of illumination light. More specifically, it provides an optical device and illumination method for uniformizing illumination light that suppresses the occurrence of bias in the intensity distribution while suppressing fluctuations in the irradiation position on the target object such as a sample. [Means for solving the problem]

[0007] An optical device according to one aspect of this embodiment includes a light source that generates illumination light, an integrator optical element that homogenizes the illumination light, a focusing element that focuses the illumination light to illuminate a target object, a deflection element that is positioned downstream of the integrator optical element and upstream of the focusing element with respect to the light source, and is positioned conjugate to the illumination surface of the target object, and a drive unit that drives the deflection element to change the direction of the illumination light emitted from the deflection element.

[0008] In the optical device described above, the integrator optical element may homogenize the illumination light such that the difference between the average intensity of the illumination light in the central part of the output surface from which the illumination light is emitted and the average intensity of the illumination light in the peripheral part of the output surface is smaller than the difference between the average intensity of the illumination light in the central part of the incident surface from which the illumination light is incident and the average intensity of the illumination light in the peripheral part of the incident surface.

[0009] The optical device described above further includes a light detection unit that detects an image of the target object illuminated by the illumination light, and the first period in which the light detection unit detects one of the images on the illumination surface may be longer than the control period in which the drive unit changes the direction of the illumination light emitted from the deflection element.

[0010] In the optical device described above, the drive unit performs a second cycle in which the direction of the illumination light is regularly varied in a predetermined direction and order for each control cycle, and the first cycle may be an approximate integer multiple of the second cycle.

[0011] In the optical device described above, the drive unit may drive the deflection element such that the direction of the illumination light varies in a first direction and a second direction perpendicular to each other.

[0012] In the optical device described above, the emission surface from which the illumination light is emitted in the integrator optical element is rectangular in shape, having two opposing sides extending in one direction and two opposing sides extending in another direction perpendicular to the one direction, wherein the first direction corresponds to the one direction and the second direction corresponds to the other direction.

[0013] In the optical apparatus described above, the integrator optical element may homogenize the illumination light generated by the light source, the deflection element may deflect the direction of the illumination light homogenized by the integrator optical element, and the focusing element may focus the illumination light whose direction has been deflected by the deflection element to illuminate the target object.

[0014] In the optical device described above, the integrator optical element includes a rectangular rod having a first end face and a second end face opposite the first end face, wherein the first end face includes an incident surface into which the illumination light is incident, and the second end face may include an exit surface from which the illumination light is emitted.

[0015] In the optical device described above, the integrator optical element may include a fly-eye lens in which a plurality of minute lenses are arranged in a plane perpendicular to the optical axis of the illumination light.

[0016] An illumination method according to one aspect of this embodiment comprises the steps of: generating illumination light with a light source; homogenizing the illumination light with an integrator optical element; focusing the illumination light with a light-gathering element to illuminate a target object; and driving a deflection element, which is positioned after the integrator optical element and before the light-gathering element with respect to the light source, so as to vary the direction of the illumination light emitted from the deflection element, which is positioned conjugate to the illumination surface of the illumination light on the target object.

[0017] In the above illumination method, in the step of homogenizing the illumination light with the integrator optical element, the integrator optical element may homogenize the illumination light such that the difference between the average intensity of the illumination light in the central part of the emission surface from which the illumination light is emitted and the average intensity of the illumination light in the peripheral part of the emission surface is smaller than the difference between the average intensity of the illumination light in the central part of the incidence surface from which the illumination light is incident and the average intensity of the illumination light in the peripheral part of the incidence surface.

[0018] The above illumination method further includes a step of detecting an image of the target object illuminated by the illumination light using a photodetector, wherein the first period in which the photodetector detects one of the images on the illumination surface may be longer than the control period in which the drive unit changes the direction of the illumination light emitted from the deflection element.

[0019] In the above-described lighting method, in the step of driving the deflection element with the drive unit, the drive unit performs a second cycle in which the direction of the illumination light is regularly varied in a predetermined direction and order for each control cycle, and the first cycle may be an approximate integer multiple of the second cycle.

[0020] In the above-described illumination method, in the step of driving the deflection element by the drive unit, the drive unit may drive the deflection element so that the direction of the illumination light varies in a first direction and a second direction perpendicular to each other.

[0021] In the above-described illumination method, in the step of homogenizing the illumination light by the integrator optical element, the emission surface from which the illumination light exits in the integrator optical element is rectangular, having two opposing sides extending in one direction and two opposing sides extending in another direction orthogonal to the one direction, the first direction may correspond to the one direction, and the second direction may correspond to the other direction.

[0022] In the above-described illumination method, in the step of homogenizing the illumination light by the integrator optical element, the integrator optical element homogenizes the illumination light generated by the light source. In the step of driving the deflection element by the drive unit, the deflection element varies the direction of the illumination light homogenized by the integrator optical element. In the step of condensing the illumination light by the condenser element to illuminate the target, the condenser element may condense the illumination light whose direction has been deflected by the deflection element to illuminate the target.

[0023] In the above-described illumination method, in the step of homogenizing the illumination light by the integrator optical element, the integrator optical element may include a corner rod having a first end face and a second end face opposing the first end face, the first end face may include an incident surface on which the illumination light is incident, and the second end face may include an emission surface from which the illumination light exits.

[0024] In the above-described illumination method, in the step of homogenizing the illumination light by the integrator optical element, the integrator optical element may include a fly-eye lens in which a plurality of microlenses are arranged on a surface orthogonal to the optical axis of the illumination light.

Advantages of the Invention

[0025] According to the present disclosure, there is provided an optical device and a lighting method that can more preferably improve the uniformity of illumination light.

Brief Description of the Drawings

[0026] [Figure 1] It is a configuration diagram illustrating an optical device according to Embodiment 1. [Figure 2] (a) is a diagram illustrating an observation of the pupil plane when a predetermined aperture stop is inserted into the light emitting surface of the integrator optical element according to Embodiment 1, (b) is a diagram illustrating an observation of the pupil plane according to Embodiment 1, and (c) schematically illustrates a variation in the position of the grating due to a variation in the direction of the illumination light emitted from the deflection element according to Embodiment 1. [Figure 3] It is a diagram illustrating an irradiation surface illuminated by illumination light in the optical device according to Embodiment 1. [Figure 4] It is a configuration diagram illustrating an optical device according to Modification 1 of Embodiment 1. [Figure 5] It is a configuration diagram illustrating an optical device according to Modification 2 of Embodiment 1. [Figure 6] It is a flowchart diagram illustrating the lighting method according to Embodiment 1. [Figure 7] It is a configuration diagram illustrating an optical device according to Comparative Example 1. [Figure 8] It is a configuration diagram illustrating an optical device according to Comparative Example 2. [Figure 9] It is a configuration diagram illustrating an optical device according to Embodiment 2. [Figure 10] It is a configuration diagram illustrating an optical device according to Modification 1 of Embodiment 2. [Figure 11] It is a flowchart diagram illustrating the lighting method according to Embodiment 2. [[ID=4I]]

Modes for Carrying Out the Invention

[0027] Embodiments of the present disclosure will be described below with reference to the drawings. The following description illustrates preferred embodiments of the present disclosure and does not limit the scope of the present disclosure to the following embodiments. In the following description, the same reference numerals indicate substantially the same thing.

[0028] (Embodiment 1) The optical apparatus and illumination method according to Embodiment 1 will now be described. The optical apparatus of this embodiment may include an illumination device that illuminates an object to be illuminated with illumination light, or it may include an inspection device that inspects an object to be inspected that has been illuminated with illumination light. The object to be illuminated and the object to be inspected may be referred to as the target object.

[0029] <Inspection equipment> Figure 1 is a diagram illustrating an optical device according to Embodiment 1. As shown in Figure 1, the optical device 1 according to this embodiment includes a light source 10, an integrator optical element 20, a deflection element 30, light-gathering elements 41 to 46, and a drive unit 50. The optical device 1 may further include optical components other than those described above, such as lenses and mirrors. The optical device 1 is, for example, an illumination device for illuminating an object 60.

[0030] The light source 10 generates illumination light L1. The light source 10 may be, for example, a laser light source that generates laser light containing a predetermined wavelength, or a light source such as a lamp that generates light with a broadband of wavelengths including white light. Therefore, the illumination light L1 may be laser light containing a predetermined wavelength, or continuous light containing a broadband of wavelengths such as white light. When the illumination light L1 is laser light, a diffraction grating may be placed between the light source 10 and the integrator optical element 20. This can reduce speckle noise. The illumination light L1 generated by the light source 10 is emitted from the light source 10.

[0031] Here, for the sake of explaining the optical device 1, we introduce an XYZ Cartesian coordinate system. The direction of the principal optical axis of the illumination light L1 emitted from the light source 10 is defined as the Z-axis direction. The two directions perpendicular to the Z-axis direction are defined as the X-axis direction and the Y-axis direction.

[0032] Illumination light L1 emitted from the light source 10 is incident on the light-gathering element 41. The light-gathering element 41 includes, for example, a lens or an aspherical mirror having a focal point. Hereafter, the light-gathering element 41 will be assumed to be a lens. The same applies to the light-gathering elements 42 to 46 described later. The light-gathering element 41 converts the incident illumination light L1 into parallel light. The illumination light L1 converted into parallel light is incident on the light-gathering element 42. The illumination light L1 incident on the light-gathering element 42 is focused by the light-gathering element 42. The light-gathering element 42 focuses the illumination light L1 onto the integrator optical element 20. As a result, the illumination light L1 is incident on the integrator optical element 20.

[0033] The integrator optical element 20 homogenizes the incident illumination light L1. In other words, the integrator optical element 20 homogenizes the illumination light L1 generated by the light source 10. The integrator optical element 20 may be, for example, a rectangular rod-shaped transparent member or a fly-eye lens containing multiple microlenses. When used in an EUV optical system, the integrator optical element 20 may be a hollow rod. A rectangular rod-shaped transparent member is simply called a rectangular rod 21.

[0034] The rectangular rod 21 has a first end face 21a and a second end face 21b. The second end face 21b is the surface opposite to the first end face 21a. The first end face 21a faces the -Z axis direction, and the second end face 21b faces the +Z axis direction. The first end face 21a faces the light source 10 side, and the second end face 21b faces the deflection element 30 side. The first end face 21a includes an incident surface into which the illumination light L1 is incident, and the second end face 21b includes an exit surface into which the illumination light L1 is emitted.

[0035] The first end face 21a may be rectangular in shape, having two opposing sides extending in the X-axis direction and two opposing sides extending in the Y-axis direction. Therefore, the incident surface on which the illumination light L1 is incident in the integrator optical element 20 may be rectangular in shape. The second end face 21b may be rectangular in shape, having two opposing sides extending in the X-axis direction and two opposing sides extending in the Y-axis direction. Therefore, the exit surface on which the illumination light L1 is emitted in the integrator optical element 20 may be rectangular in shape.

[0036] The integrator optical element 20 may homogenize the illumination light L1 such that the difference between the average intensity of the illumination light L1 in the central part of the exit surface and the average intensity of the illumination light L1 in the peripheral part of the exit surface is smaller than the difference between the average intensity of the illumination light L1 in the central part of the incident surface and the average intensity of the illumination light L1 in the peripheral part of the incident surface.

[0037] The illumination light L1 is focused onto the first end face 21a by the light-gathering element 42. As a result, the illumination light L1 is incident on the first end face 21a at various incident angles. The illumination light L1 incident on the first end face 21a travels through the inside of the square rod 21 with a component in the +Z axis direction. The illumination light L1 travels through the inside of the square rod 21, reflecting off the sides, with a component in the +Z axis direction. Therefore, the illumination light L1 that exits from the square rod 21 exits from the second end face 21b at various exit angles. The illumination light L1 that exits from the second end face 21b of the square rod 21 is incident on the light-gathering element 43.

[0038] The light-gathering element 43 converts the incident illumination light L1 into parallel light. The illumination light L1 converted into parallel light is incident on the light-gathering element 44. A pupil plane H1 of the illumination light L1 is formed between the light-gathering element 43 and the light-gathering element 44. The illumination light L1 incident on the light-gathering element 44 is focused by the light-gathering element 44. The light-gathering element 44 focuses the illumination light L1 onto the deflection element 30. As a result, the illumination light L1 is incident on the deflection element 30.

[0039] The deflection element 30 deflects the direction of propagation of the incident illumination light L1. In other words, the deflection element 30 changes the direction in which the illumination light L1 travels. Specifically, the deflection element 30 changes the direction of the principal optical axis of the incident illumination light L1 and causes it to be emitted. The deflection element 30 deflects the direction of propagation of the illumination light L1, which has been homogenized by the integrator optical element 20. The deflection element 30 may include, for example, a galvanometer mirror 31. If the deflection element 30 includes a galvanometer mirror 31, the deflection element 30 deflects the direction of propagation of the incident illumination light L1 by reflecting it. The direction of propagation is sometimes simply referred to as direction.

[0040] While a galvanometer mirror 31 is shown as an example of the deflection element 30, it is not limited to this. For example, the deflection element 30 may include a piezo steering mirror and a polygon mirror. Furthermore, the deflection element 30 is not limited to the mirrors mentioned above, but may also include an optical element that transmits illumination light L1. Such an optical element that transmits illumination light L1 may deflect the direction of propagation of the illumination light L1. In addition, the deflection element 30 may include at least one of the following: a mirror that reflects the illumination light L1, an optical element that transmits the illumination light L1, a beam shifter that shifts the direction of propagation of the illumination light L1, an acousto-optic element that shifts the direction of propagation of the illumination light L1, and an electro-optic element that deflects the direction of propagation of the illumination light L1. Here, the electro-optic element includes an element that controls the path of light by utilizing a change in refractive index due to voltage, and includes, for example, a KTN optical scanner using a KTN crystal of an oxide crystal containing potassium, tantalum, and niobium. Furthermore, the deflection element 30 may include a diffracting plate, a diffracting plate, a polarizing plate, an optical fiber, a prism, and the like.

[0041] The deflection element 30 is attached to the drive unit 50. The drive unit 50 drives the deflection element 30 to change the direction of travel of the illumination light L1 emitted from the deflection element 30. That is, the drive unit 50 drives the deflection element 30 so that the direction of travel of the illumination light L1 emitted from the deflection element 30 at a first time is different from the direction of travel of the illumination light L1 emitted from the deflection element 30 at a second time. For example, the drive unit 50 may include a motor driver. The motor driver controls a motor that changes the reflection angle of the mirror by changing the attitude of the deflection element 30, etc. The illumination light L1 whose direction of travel has been deflected by the deflection element 30 is incident on the light concentrating element 45. That is, the illumination light L1 emitted from the deflection element 30 at a first time is incident on the light concentrating element 45 at a different angle of incidence than the illumination light L1 emitted from the deflection element 30 at a second time.

[0042] The focusing element 45 converts the incident illumination light L1 into parallel light. The illumination light L1 converted into parallel light is incident on the focusing element 46. A pupil plane H2 of the illumination light L1 is formed between the focusing element 45 and the focusing element 46. The illumination light L1 incident on the focusing element 46 is focused by the focusing element 46. The focusing element 46 focuses the illumination light L1 to illuminate the target object 60. In other words, the focusing element 46 focuses the illumination light L1 whose direction of travel has been deflected by the deflection element 30 to illuminate the target object 60. For example, the focusing element 46 focuses the illumination light L1 to illuminate the illumination surface 61 of the target object 60. In this way, the optical device 1 illuminates the target object 60.

[0043] The deflection element 30 is positioned after the integrator optical element 20 and before the light-gathering element 46 when viewed from the light source 10. The deflection element 30 is positioned conjugate to the irradiation surface 61 of the illumination light L1 on the target object 60. Because the deflection element 30 is positioned conjugate to the irradiation surface 61, deviation of the illumination light L1 from a predetermined irradiation position can be suppressed. The drive unit 50 drives the deflection element 30 in a state where the deflection element 30 is in contact with both the focal position of the light-gathering element 44 and the focal position of the light-gathering element 45. For example, if the deflection element 30 is a mirror, the focal position of the light-gathering element 44 and the focal position of the light-gathering element 45 coincide. The drive unit 50 drives the deflection element 30 so that the attitude of the deflection element 30 changes with the light-gathering position as the pivot point. In other words, the drive unit 50 drives the deflection element 30 so that the focal positions of the light-gathering element 44 and the light-gathering element 45 remain on or near the surface of the deflection element 30 before and after the attitude of the deflection element 30 changes. If the irradiation surface 61 of the illumination light L1 on the target object 60 is considered as a point such as a focal point, then it can be said that the deflection element 30 is positioned at a position conjugate to the irradiation point of the illumination light L1 on the target object 60.

[0044] Figure 2(a) is an example of observing the pupil surface H1 when a predetermined aperture diaphragm is inserted into the exit surface of the integrator optical element 20 according to Embodiment 1. As shown in Figure 2(a), a bias in the discrete intensity distribution of illumination light L1 is observed. Such a grid-like bias in the discrete intensity distribution also occurs in the second example configuration of Patent Document 1, as mentioned above. Furthermore, such a grid-like bias in the discrete intensity distribution also appears when a fly-eye lens is used instead of the square rod 21. Multiple grids are generated, arranged in the horizontal and vertical directions. These vertical and horizontal orientations correspond to the vertical and horizontal directions of the rectangle of the integrator optical element 20.

[0045] Figure 2(b) is an example of an observation of the pupil surface H2 according to Embodiment 1. As shown in Figure 2(b), the bias in the grid-like discrete intensity distribution is eliminated in the pupil surface H2. The reason why the bias in the discrete intensity distribution is eliminated in the pupil surface H2, which is located after the deflection element 30, will be explained below.

[0046] Figure 2(c) schematically illustrates the change in the position of the grid due to the change in the direction of the illumination light L1 emitted from the deflection element 30 according to Embodiment 1. As shown in Figure 2(c), the drive unit 50 changes the direction of the illumination light L1 emitted from the deflection element 30, causing the position of each grid to move slightly as indicated by the arrows in the figure. As a result, the intensity distribution at the pupil H2 can be made unbiased, as shown in Figure 2(b). It is preferable for the drive unit 50 to change the direction of propagation of the illumination light L1 emitted from the deflection element 30 in two directions. For example, it is preferable for the drive unit 50 to change the direction of propagation of the illumination light L1 emitted from the deflection element 30 in directions perpendicular to each other, or in directions corresponding to the vertical and horizontal directions on the rectangular emission surface of the integrator optical element 20. In other words, the drive unit 50 drives the deflection element 30 so that the direction of the illumination light L1 changes in a first direction and a second direction that are perpendicular to each other. Furthermore, to add to the explanation, if the deflection direction of the illumination light L1 by the deflection element 30 is fixed without changing, the intensity distribution at pupil H2 will be the same as in Figure 2(a).

[0047] Figure 3 is a diagram illustrating the illumination surface 61 illuminated by the illumination light L1 in the optical device 1 according to Embodiment 1. As shown in Figure 3, the surface parallel to the main surface of the object 60 (e.g., the surface to be illuminated or the surface to be inspected) is defined as the αβ surface. The first direction parallel to the αβ surface is defined as the α-axis direction, and the second direction parallel to the αβ surface and perpendicular to the first direction is defined as the β-axis direction. The direction perpendicular to the αβ surface is defined as the γ-axis direction. The illumination surface 61 is the illumination spot, i.e., the focal point, when illuminating the object 60. Therefore, the illumination surface 61 may be interpreted as the illumination point 61 or the focal point 61 as appropriate. The illumination surface 61 is parallel to the αβ surface, or is included in the αβ surface. The drive unit 50 may drive the deflection element 30 in the α-axis direction (first direction) parallel to the illumination surface 61, and in the β-axis direction (second direction) parallel to the illumination surface 61 and perpendicular to the α-axis direction. In this case, the α-axis direction may correspond to the X-axis direction and the β-axis direction may correspond to the Y-axis direction on the incident and exit surfaces of the integrator optical element 20. In the optical device 1 according to this embodiment, even if the deflection element 30 is driven, the position of the illumination surface 61 on the target object 60 (the focal point on the target object 60) does not move. Therefore, for example, when illuminating multiple positions included in a predetermined area 62 such as the illumination target area or inspection target area of ​​the target object 60, the stage on which the target object 60 is placed is moved. This causes the illumination surface 61 (focal point) to scan the target object 60. The stage may move the target object 60 along the αβ plane, or in addition to this, the target object 60 may be moved in the γ-axis direction. Note that the method of scanning the illumination surface 61 on the target object 60 is not limited to the stage.

[0048] <Example 1> Figure 4 is a diagram illustrating an optical device 1a according to a modified example 1 of Embodiment 1. As shown in Figure 4, the optical device 1a may include deflection elements 30a and 30b instead of deflection element 30. Deflection elements 30a and 30b may be, for example, galvanometer mirrors 31 and 32, respectively. The optical device 1a may include drive units 51 and 52 instead of drive unit 50. Deflection element 30a is attached to drive unit 51. Deflection element 30b is attached to drive unit 52. A light-gathering element 47 and a light-gathering element 48 are arranged between deflection element 30a and deflection element 30b.

[0049] The light-gathering element 44 focuses the illumination light L1 onto the deflection element 30a. As a result, the illumination light L1 is incident on the deflection element 30a.

[0050] The deflection element 30a deflects the direction of travel of the incident illumination light L1. Therefore, the deflection element 30a deflects the direction of travel of the illumination light L1 that has been homogenized by the integrator optical element 20. The drive unit 51 drives the deflection element 30a to vary the direction of travel of the illumination light L1 incident on the deflection element 30a. The illumination light L1 whose direction of travel has been deflected by the deflection element 30a is incident on the light-gathering element 47.

[0051] The light-gathering element 47 converts the incident illumination light L1 into parallel light. The illumination light L1 converted into parallel light is incident on the light-gathering element 48. A pupil plane H3 of the illumination light L1 is formed between the light-gathering element 47 and the light-gathering element 48. The illumination light L1 incident on the light-gathering element 48 is focused by the light-gathering element 48. The light-gathering element 48 focuses the illumination light L1 onto the deflection element 30b. As a result, the illumination light L1 is incident on the deflection element 30b.

[0052] The deflection element 30b deflects the direction of travel of the incident illumination light L1. The drive unit 52 drives the deflection element 30b to change the direction of travel of the illumination light L1 incident on the deflection element 30b. The illumination light L1, whose direction of travel has been deflected by the deflection element 30b, is incident on the light-gathering element 45. The light-gathering element 45 converts the incident illumination light L1 into parallel light. The illumination light L1 converted into parallel light is incident on the light-gathering element 46. A pupil plane H2 of the illumination light L1 is formed between the light-gathering element 45 and the light-gathering element 46. The illumination light L1 incident on the light-gathering element 46 is focused by the light-gathering element 46. The light-gathering element 46 focuses the illumination light L1 to illuminate the target object 60. In this way, the optical device 1a illuminates the target object 60.

[0053] In this modified example, the direction in which the direction of illumination light L1 emitted from the deflection element 30a is changed by the drive unit 51 and the direction in which the direction of illumination light L1 emitted from the deflection element 30b is changed by the drive unit 52 are different from each other, for example, by 90 degrees. Thus, in the optical device 1a according to Modified Example 1, the drive units 51 and 52 each use a plurality of deflection elements 30a and 30b to change the direction of illumination light L1 emitted from the deflection elements 30a and 30b in two directions. The drive unit 51 may, for example, drive the deflection element 30a so that the illumination light L1 moves in a direction equivalent to the X-axis direction, thereby changing the direction of travel of the illumination light L1. The drive unit 52 may drive the deflection element 30b so that the illumination light L1 moves in a direction equivalent to the Y-axis direction, thereby changing the direction of travel of the illumination light L1. Since the drive units 51 and 52 drive the deflection elements 30a and 30b in one direction, respectively, the same effect can be obtained even when it is difficult to change the direction of light in two directions with a single deflection element 30.

[0054] <Modification 2> Figure 5 is a diagram illustrating an optical device 1b according to a modified example 2 of Embodiment 1. As shown in Figure 5, the optical device 1b includes a fly-eye lens 22 as an integrator optical element 20. The fly-eye lens 22 includes a plurality of microlenses arranged in the XY plane. In other words, the integrator optical element 20 includes a fly-eye lens 22 in which a plurality of microlenses are arranged in a plane perpendicular to the optical axis of the illumination light L1. The fly-eye lens 22 is positioned between the light-gathering element 41 and the light-gathering element 44. Therefore, the light-gathering elements 42 and 43 may be omitted.

[0055] The illumination light L1 that has passed through the light-gathering element 41 enters the fly-eye lens 22. The illumination light L1 that has passed through the fly-eye lens 22 enters the light-gathering element 44. The other configurations are the same as those of Embodiment 1. Even with this configuration, the uniformity of the illumination light L1 can be improved.

[0056] <Lighting method> Next, the illumination method of this embodiment will be described. Figure 6 is a flowchart illustrating the illumination method according to Embodiment 1. As shown in Figure 6, the illumination method comprises a step S11 for generating illumination light, a step S12 for homogenizing the illumination light, a step S13 for changing the direction of propagation of the illumination light, and a step S14 for focusing the illumination light L1 to illuminate the target object 60.

[0057] In step S11, the light source 10 generates illumination light L1.

[0058] Next, in step S12, the integrator optical element 20 homogenizes the illumination light L1 generated by the light source 10. In step S12, the integrator optical element 20 may homogenize the illumination light L1 such that the difference between the average intensity of the illumination light L1 in the central part of the output surface and the average intensity of the illumination light L1 in the peripheral part of the output surface is smaller than the difference between the average intensity of the illumination light L1 in the central part of the incident surface and the average intensity of the illumination light L1 in the peripheral part of the incident surface.

[0059] In step S12, the exit surface from which the illumination light L1 is emitted in the integrator optical element 20 may be rectangular in shape, having two opposing sides extending in one direction and two opposing sides extending in the other direction. For example, the integrator optical element 20 may include a rectangular rod 21 having a first end face 21a and a second end face 21b opposite the first end face 21a. The first end face 21a may include an incident surface from which the illumination light L1 is incident, and the second end face 21b may include an exit surface from which the illumination light L1 is emitted. The integrator optical element 20 may also include a fly-eye lens in which a plurality of microlenses are arranged on a plane perpendicular to the optical axis of the illumination light L1.

[0060] Next, in step S13, the deflection element 30 is driven by the drive unit 50 to change the direction of propagation of the illumination light L1 emitted from the deflection element 30. Here, the deflection element 30 is positioned after the integrator optical element 20 and before the light-gathering element 46 when viewed from the light source 10. Furthermore, the deflection element 30 is positioned conjugate to the illumination surface 61 of the target object 60.

[0061] In step S13, the drive unit 50 may drive the deflection element 30 in a first direction parallel to the irradiation surface 61 of the target object 60, and in a second direction parallel to the irradiation surface 61 and perpendicular to the first direction. Here, the first direction may correspond to one direction of the second end face 21b of the square rod 21, and the second direction may correspond to the other direction of the second end face 21b of the square rod 21.

[0062] Next, in step S14, the illumination light L1 is focused by the light-gathering element 46 to illuminate the target object 60. In this way, the target object 60 can be illuminated with the illumination light L1.

[0063] Next, before describing the effects of this embodiment, Comparative Examples 1 to 3 will be described. Then, the effects of this embodiment will be described in comparison with Comparative Examples 1 to 3. Note that Comparative Examples 1 to 3 also fall within the scope of the technical concept of this embodiment.

[0064] <Comparative Example 1> Figure 7 is a diagram illustrating the configuration of an optical device 101 according to Comparative Example 1. As shown in Figure 7, the optical device 101 of Comparative Example 1 is modeled after the optical device of Patent Document 1. The optical device 101 of Comparative Example 1 comprises a laser light source 110, a square rod 120, a diffraction grating 121, and a galvanometer mirror 130. Laser light L11 generated by the laser light source 110 is reflected by the galvanometer mirror 130 and then incident on the diffraction grating 121. Illumination light L12, which includes multiple diffracted light beams diffracted by the diffraction grating 121, is incident on the square rod 120. The illumination light L12 incident on the square rod 120 undergoes repeated total internal reflection within the square rod 120. As a result, the illumination light L12 is made uniform. The illumination light L12 emitted from the square rod 120 illuminates the target object.

[0065] In the optical apparatus 101 of Comparative Example 1, the diffraction grating 121 and the angular rod 120 are positioned on the lower side of the galvanometer mirror 130 as viewed from the laser light source 110. Therefore, the incident position and incident angle of the laser light L11 incident on the diffraction grating 121 and the angular rod 120 fluctuate. As a result, the illumination position in which the illumination light L12 emitted from the angular rod 120 illuminates the target object fluctuates frequently, and as mentioned above, the target object cannot be stably illuminated.

[0066] <Comparative Example 2> Figure 8 is a diagram illustrating the configuration of an optical device 102 according to Comparative Example 2. As shown in Figure 8, the optical device 102 of Comparative Example 2 is modeled after an optical device according to another example in Patent Document 1. The optical device 102 of Comparative Example 2 comprises a laser light source 110, a square rod 120, and a diffraction grating 122. Laser light L11 generated by the laser light source 110 is incident on the rotating diffraction grating 122. Illumination light L12, which includes multiple diffracted light beams diffracted by the diffraction grating 121, is incident on the square rod 120. The illumination light L12 incident on the square rod 120 undergoes repeated total internal reflection within the square rod 120. As a result, the illumination light L12 is made uniform. The illumination light L12 emitted from the square rod 120 illuminates the target object.

[0067] The optical device 102 of Comparative Example 2 does not have a galvanometer mirror 130. As mentioned above, in the optical device 102 of Comparative Example 2, the light intensity distribution corresponding to the number of times the illumination light L12 is reflected within the angular rod 120 appears discretely in a grid pattern, so further efforts are needed to make it more uniform.

[0068] Next, the effects of this embodiment will be explained. The optical devices 1, 1a, and 1b of this embodiment will be collectively referred to as optical device 1. The deflection elements 30, 30a, and 30b will be collectively referred to as deflection element 30. Optical device 1 includes an integrator optical element 20 that homogenizes the illumination light L1, as well as a deflection element 30 that deflects the direction of propagation of the illumination light L1. Therefore, the homogenization by the deflection element 30 can be superimposed on the homogenization by the integrator optical element 20. This makes the intensity distribution in a cross-section perpendicular to the optical axis of the illumination light L1 a continuous distribution, thereby improving uniformity.

[0069] In contrast, Comparative Example 2 does not have a deflection element 30. Therefore, it cannot suppress the discrete and discontinuous distribution that reflects the reflection in the angular rod 120.

[0070] In this embodiment, the deflection element 30 is positioned conjugate to the illumination surface 61. This suppresses deviation of the illumination light L1 from a predetermined illumination position, thereby improving the uniformity of the illumination light L1. Furthermore, the deflection element 30 is positioned after the integrator optical element 20. This allows the incident position and incident angle of the laser light L11 incident on the angular rod 120 to be kept constant, thereby improving the uniformity of the illumination light L12.

[0071] In contrast, in Comparative Example 1, the galvanometer mirror 130 is not positioned conjugate to the illumination surface 61. Therefore, it is difficult to suppress the shift in the illumination position of the illumination light L1. Also, in Comparative Example 1, since the galvanometer mirror 130 is positioned before the square rod 120, it is difficult to suppress the shift in the illumination position where the illumination light L12 emitted from the square rod 120 illuminates the target object from a predetermined position.

[0072] The drive unit 50 uses the deflection element 30 to change the direction of the illumination light L1 emitted from the deflection element 30 in two directions. Therefore, it is easy to improve the uniformity of the illumination light L1 that illuminates the illumination surface 61.

[0073] <Embodiment 2> Next, Embodiment 2 will be described. The optical device 2 of this embodiment further includes a light detection unit. Figure 9 is a configuration diagram illustrating the optical device 2 according to Embodiment 2. As shown in Figure 9, the optical device 2 further includes a light detection unit 70 and a separation member 49 compared to the optical device 1 of Embodiment 1.

[0074] The separating member 49 is, for example, positioned between the light-gathering element 45 and the light-gathering element 46. The illumination light L1 that has passed through the light-gathering element 45 is incident on the separating member 49. The separating member 49 includes, for example, a half-mirror. The separating member 49 reflects a portion of the incident illumination light L1 and transmits a portion of it. The separating member 49 may also be an unpolarized beam splitter.

[0075] The illumination light L1 that has passed through the light-gathering element 45 is incident on the separating member 49. The separating member 49 reflects a portion of the incident illumination light L1 and transmits the other portion. The illumination light L1 that has passed through the separating member 49 is incident on the light-gathering element 46. The light-gathering element 46 focuses the illumination light L1 to illuminate the target object 60 and also focuses the light L2 from the target object 60 that has been illuminated by the illumination light L1. The light L2 from the target object 60 includes reflected light reflected by the target object 60, scattered light scattered by the target object 60, diffracted light diffracted by the target object 60, and excited light excited by the target object 60. The light L2 focused by the light-gathering element 46 passes through the light-gathering element 46 and is incident on the separating member 49. The separating member 49 reflects a portion of the incident light L2 and transmits the other portion. The light L2 reflected by the separating member 49 is incident on the light detection unit 70.

[0076] The light detection unit 70 detects an image of the target object 60 illuminated by the illumination light L1. At this time, it may detect an image of the target object 60 at the position of the illumination surface 61. The light detection unit 70 may include, for example, a TDI (Time Delay Integration) sensor or an imaging device.

[0077] The period in which the light detection unit 70 detects one image on the illuminated surface 61 (referred to as the first period) may be longer than the control period in which the drive unit 50 changes the direction of the illumination light L1 emitted from the deflection element 30. In the second period, the drive unit 50 regularly changes the direction of the illumination light L1 in a predetermined direction and order for each control period. That is, the drive unit 50 changes the direction of the illumination light L1 emitted from the deflection element 30 for each control period, and in the second period, it repeats a cycle of changing the direction of the illumination light L1 in a predetermined direction in a predetermined order. In this case, for example, the first period may be approximately an integer multiple of the second period. Also, the second period may be approximately an integer multiple of the control period. Note that "approximately an integer multiple" means an integer multiple within a range that includes the measurement error of the timer that measures time, errors such as delays in the detection operation of the light detection unit 70, and errors such as delays in the drive operation of the drive unit 50.

[0078] The second period may be shorter than the first period. That is, the drive unit 50 may vary the direction of the illumination light L1 emitted from the deflection element 30 in a second period shorter than the charge accumulation time required for the photodetector 70 to detect one image of the illuminated surface 61. The drive unit 50 may also vary the direction of the illumination light L1 emitted from the deflection element 30 at a rate greater than the frame rate of the photodetector 70 (the number of images detected and acquired by the photodetector 70 per second). The rate may refer to the number of times the drive unit 50 varies the direction of the illumination light L1 emitted from the deflection element 30 per second. For this reason, the rate may also be called the variation rate. The drive unit 50 may vary the direction of the illumination light L1 emitted from the deflection element 30 regularly or randomly in a control period shorter than the charge accumulation time required for the photodetector 70 to detect one image of the illuminated surface 61. Furthermore, the drive unit 50 may regularly or randomly change the direction of the illumination light L1 emitted from the deflection element 30 at a rate greater than the frame rate of the light detection unit 70 (the number of images detected and acquired by the light detection unit 70 per second). Regularly changing the direction of the illumination light L1 may include changing the direction of the illumination light L1 in directions selected in a predetermined order. Randomly changing the direction of the illumination light L1 may include changing the direction of the illumination light L1 in a direction randomly selected from a predetermined set of directions, or it may include changing the direction of the illumination light L1 in random directions.

[0079] It is preferable that the first period and the charge accumulation time are set to be sufficiently larger than the control period and the second period so that the variation in the direction of the illumination light L1, which is performed regularly or randomly with each control period, or the regular variation in the direction of the illumination light L1, which is performed with each second period, is sufficient to eliminate discrete intensity biases.

[0080] <Example 1> Figure 10 is a configuration diagram illustrating an optical device 2a according to Modification 1 of Embodiment 2. As shown in Figure 10, the optical device 2a in this modification does not have a separating member 49. Instead, the optical device 2a has a light-collecting element 49a. Also, the light detection unit 70 is positioned on the +Y axis side of the target object 60. In Figure 9, the light detection unit 70 detects light L2 including reflected light reflected by the target object 60. On the other hand, as shown in Figure 10, in the optical device 2a of Modification 1, the light detection unit 70 detects light L2 including transmitted light that has passed through the target object 60. Even with this configuration, the same functions and effects as in Embodiment 2 can be obtained.

[0081] Figure 11 is a flowchart illustrating an example of the illumination method according to Embodiment 2. As shown in Figure 11, the illumination method of this embodiment further includes a step S15 for detecting an image of the target object 60, compared to the illumination method of Embodiment 1.

[0082] In step S15, the photodetector 70 detects an image of the target object 60 illuminated by the illumination light L1. In step S15, the first period in which the photodetector 70 detects one image of the illuminated surface 61 is longer than the control period in which the drive unit 50 changes the direction of the illumination light L1 emitted from the deflection element 30.

[0083] In this embodiment, in step S13, the drive unit 50 may vary the direction of travel of the illumination light L1 emitted from the deflection element 30 in a second cycle shorter than the charge accumulation time for the photodetector 70 to detect one image. Alternatively, in step S13, the drive unit 50 may vary the direction of travel of the illumination light L1 emitted from the deflection element 30 at a rate greater than the frame rate of the photodetector 70. The other configurations are the same as those of the embodiment 1 described above.

[0084] In this embodiment, the first period in which the photodetector 70 detects one image of the illuminated surface 61 is longer than the control period in which the drive unit 50 varies the direction of the illumination light L1 emitted from the deflection element 30. Furthermore, the first period is longer than the second period in which the drive unit 50 regularly varies the direction of the illumination light L1 in a predetermined direction. Specifically, for example, the first period is an integer multiple of the second period. With this configuration, the discrete distribution of illumination light L1 reflected inside the angular rod 120 can be smoothed out with integer multiple scans, thereby improving the resolution of the image on the illuminated surface 61 of the target object 60 detected by the photodetector 70. Other configurations and effects are described in Embodiment 1 and each of its modifications.

[0085] While embodiments of this disclosure have been described above, this disclosure includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the embodiments described above. Furthermore, combinations of the configurations of Embodiments 1 and 2, each modified example, and each comparative example also fall within the scope of the technical concept of this disclosure. [Explanation of Symbols]

[0086] 1, 1a, 1b, 2, 2a optical equipment 10 light source 20 Integrator Optical Elements 21 Square Rod 21a First end surface 21b 2nd end face 22 Fly-eye lenses 30, 30a, 30b deflection element 31, 32 Galvano Mirror 41, 42, 43, 44, 45, 46, 47, 48 Light-gathering element 49 Separation member 49b Light-gathering element 50, 51, 52 Drive unit 60 Object 61 Irradiation surface 62 Predetermined area 70 Light detection unit 101, 102, 103 Optical equipment 110 Laser light source 120 square rod 121, 122 Diffraction gratings 130 Galvano Mirror 141, 142, 143 Light-gathering elements 144 Aperture H1, H2, H3 pupil plane L1, L11, L12 illumination light L2 light

Claims

1. A light source that generates illumination light, The integrator optical element that homogenizes the illumination light, A light-gathering element that focuses the aforementioned illumination light to illuminate a target object, A deflection element positioned after the integrator optical element and before the light-gathering element with respect to the light source, wherein the deflection element is positioned conjugate to the irradiation surface of the illumination light on the target object, A drive unit that drives the deflection element to change the direction of the illumination light emitted from the deflection element, An optical device equipped with an optical system.

2. The integrator optical element homogenizes the illumination light such that the difference between the average intensity of the illumination light in the central part of the emission surface from which the illumination light is emitted and the average intensity of the illumination light in the peripheral part of the emission surface is smaller than the difference between the average intensity of the illumination light in the central part of the incident surface from which the illumination light is incident and the average intensity of the illumination light in the peripheral part of the incident surface. The optical apparatus according to claim 1.

3. The system further includes a light detection unit that detects an image of the target object illuminated by the aforementioned illumination light, The first period in which the light detection unit detects one of the images on the illuminated surface is longer than the control period in which the drive unit changes the direction of the illumination light emitted from the deflection element. The optical apparatus according to claim 1 or 2.

4. The drive unit performs in the second cycle the regular variation of the direction of the illumination light in a predetermined direction and order for each control cycle. The first period is approximately an integer multiple of the second period. The optical apparatus according to claim 3.

5. The drive unit drives the deflection element so that the direction of the illumination light varies in a first direction and a second direction perpendicular to each other. The optical apparatus according to claim 1 or 2.

6. The emission surface from which the illumination light is emitted in the integrator optical element is rectangular in shape, having two opposing sides extending in one direction and two opposing sides extending in the other direction perpendicular to the one direction. The first direction corresponds to the one direction, The second direction corresponds to the other direction. The optical apparatus according to claim 5.

7. The integrator optical element homogenizes the illumination light generated by the light source, The deflection element deflects the direction of the illumination light, which has been made uniform by the integrator optical element. The light-gathering element focuses the illumination light, whose direction has been deflected by the deflection element, to illuminate the target object. The optical apparatus according to claim 1 or 2.

8. The integrator optical element includes a square rod having a first end face and a second end face opposite the first end face. The first end face includes an incident surface to which the illumination light is incident, The second end face includes an emission surface from which the illumination light is emitted. The optical apparatus according to claim 1 or 2.

9. The integrator optical element includes a fly-eye lens in which a plurality of minute lenses are arranged on a plane perpendicular to the optical axis of the illumination light. The optical apparatus according to claim 1 or 2.

10. The steps include generating illumination light using a light source, The steps include: making the illumination light uniform using an integrator optical element; The steps include: concentrating the illumination light with a light-gathering element to illuminate the target object; A deflection element is positioned after the integrator optical element and before the light-gathering element with respect to the light source, and the deflection element is driven by a drive unit to change the direction of the illumination light emitted from the deflection element, which is positioned conjugate to the illumination surface of the illumination light on the target object. A lighting method equipped with [a specific feature / feature].

11. In the step of homogenizing the illumination light using the integrator optical element, The integrator optical element homogenizes the illumination light such that the difference between the average intensity of the illumination light in the central part of the emission surface from which the illumination light is emitted and the average intensity of the illumination light in the peripheral part of the emission surface is smaller than the difference between the average intensity of the illumination light in the central part of the incident surface from which the illumination light is incident and the average intensity of the illumination light in the peripheral part of the incident surface. The lighting method according to claim 10.

12. The further step includes detecting an image of the target object illuminated by the aforementioned illumination light using a photodetector, In the step of detection by the aforementioned light detection unit, The first period in which the light detection unit detects one of the images on the illuminated surface is longer than the control period in which the drive unit changes the direction of the illumination light emitted from the deflection element. The lighting method according to claim 10 or 11.

13. In the step of driving the deflection element with the drive unit, The drive unit performs in the second cycle the regular variation of the direction of the illumination light in a predetermined direction and order for each control cycle. The first period is approximately an integer multiple of the second period. The lighting method according to claim 12.

14. In the step of driving the deflection element with the drive unit, The drive unit drives the deflection element so that the direction of the illumination light varies in a first direction and a second direction perpendicular to each other. The lighting method according to claim 10 or 11.

15. In the step of homogenizing the illumination light using the integrator optical element, The emission surface from which the illumination light is emitted in the integrator optical element is rectangular in shape, having two opposing sides extending in one direction and two opposing sides extending in the other direction perpendicular to the one direction. The first direction corresponds to the one direction, The second direction corresponds to the other direction. The illumination method according to claim 14.

16. In the step of homogenizing the illumination light using the integrator optical element, The integrator optical element homogenizes the illumination light generated by the light source, In the step of driving the deflection element with the drive unit, The deflection element changes the direction of the illumination light that has been made uniform by the integrator optical element. In the step of illuminating an object by focusing the illumination light with the light-gathering element, The light-gathering element focuses the illumination light, whose direction has been deflected by the deflection element, to illuminate the target object. The lighting method according to claim 10 or 11.

17. In the step of homogenizing the illumination light using the integrator optical element, The integrator optical element includes a square rod having a first end face and a second end face opposite the first end face. The first end face includes an incident surface to which the illumination light is incident, The second end face includes an emission surface from which the illumination light is emitted. The lighting method according to claim 10 or 11.

18. In the step of homogenizing the illumination light using the integrator optical element, The integrator optical element includes a fly-eye lens in which a plurality of minute lenses are arranged on a plane perpendicular to the optical axis of the illumination light. The lighting method according to claim 10 or 11.

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