Observation device and observation method

Abstract

This observation device comprises a light source unit including an annular illumination unit that outputs observation light having an annular illumination pattern, an irradiation unit that includes an objective lens having an observation surface of an observation object as the focal plane thereof and irradiates the observation object with the observation light, and an imaging unit that images the observation surface. The imaging unit is capable of detecting reflected light of the observation light that has passed through the irradiation unit and entered the inside of the observation object, the reflected light having passed through the observation surface and been emitted from the observation object, and passed through the irradiation unit again. The light source unit includes a focus adjustment unit capable of adjusting the focus of the light source unit so that the conjugate plane of the annular illumination unit coincides with the pupil plane of the objective lens in the optical path of the reflected light of the observation light.

Description

Observation Device and Observation Method

[0001] The present disclosure relates to an observation device and an observation method.

[0002] As a technology related to an observation device for observing an observation surface of an object to be observed, for example, an epi-illumination phase contrast microscope described in Patent Document 1 is known. In the epi-illumination phase contrast microscope described in Patent Document 1, illumination light having an annular (ring-shaped) illumination pattern is irradiated onto a sample through an objective lens. The light transmitted through the sample is reflected and guided through the objective lens to an observation unit such as a camera.

[0003] Japanese Patent Laid-Open No. 8-194160

[0004] By the way, in an observation device, for example, there may be a demand to observe damage (subsurface damage), crystal defects, voids, internal processing marks, etc. generated inside an object to be observed, and the position of the observation surface of the object to be observed and the thickness of the object to be observed are also various. In this case, in the above-described observation device, the illumination pattern of the light projected onto the observation surface may remain annular (that is, it may not be uniform illumination), and there is a possibility that the observation surface cannot be appropriately observed.

[0005] Therefore, an object of the present disclosure is to provide an observation device and an observation method capable of appropriately observing an observation surface of an object to be observed.

[0006] The observation device of the present disclosure is [1] "an observation device for observing an observation surface of an object to be observed, including a light source unit including an annular illumination unit that outputs observation light having an annular illumination pattern, an objective lens having the observation surface as a focal plane, an irradiation unit that irradiates the observation light onto the object to be observed, and an imaging unit that images the observation surface, the imaging unit can detect reflected light of the observation light that is incident on the inside of the object to be observed through the irradiation unit and is transmitted through the observation surface and exits from the object to be observed and then transmitted through the irradiation unit again, and the light source unit includes a focus adjustment unit capable of adjusting the focus of the light source unit so that the conjugate plane of the annular illumination unit coincides with the pupil plane of the objective lens in the optical path of the reflected light of the observation light".

[0007] In this observation device, the focus adjustment unit adjusts the conjugate plane of the annular illumination unit so that it coincides with the pupil plane of the objective lens in the optical path of the reflected light (the optical path after reflection). This allows the observation surface to be the Fourier plane of the annular illumination unit, preventing the illumination pattern of the light projected onto the observation surface from remaining annular. Therefore, it becomes possible to observe the observation surface appropriately.

[0008] The observation apparatus of the present invention may also be [2] "the observation apparatus described in [1], wherein the illumination unit is composed of a phase contrast objective lens." In this case, for example, a one-sided incidence transmission phase contrast microscope can be realized, in which observation light is incident from one side of the object to be observed.

[0009] The observation apparatus of the present invention may also be [3] "the observation apparatus described in [1] or [2], wherein the observation direction, which is the direction from the imaging unit toward the observation surface, and the incident direction, which is the direction in which the reflected light of the observation light that has passed through the irradiation unit and entered the interior of the object to be observed enters the observation surface, are opposite to each other." In this case, the observation surface can be observed with the observation direction and the incident direction opposite to each other.

[0010] The observation apparatus of the present invention may also be [4] "the observation apparatus according to any one of [1] to [3], wherein the focus adjustment unit includes a variable focus lens." In this case, the focus of the light source can be adjusted at high speed by the variable focus lens.

[0011] The observation apparatus of the present invention may also be [5] "the observation apparatus according to [4], further comprising another variable focus lens separate from the variable focus lens, in the focus adjustment unit." In this case, by adjusting the focal length of the other variable focus lens, it becomes possible to adjust the diameter of the annular illumination pattern of the reflected light of the observation light projected onto the pupil of the objective lens.

[0012] The observation apparatus of the present invention may also be [6] "the observation apparatus according to [4], wherein the focus adjustment unit includes a moving mechanism for moving the optical element included in the light source unit in the optical axis direction of the observation light." In this case, by appropriately moving the optical element with the moving mechanism, it is possible to adjust the diameter of the annular illumination pattern of the reflected light of the observation light projected onto the pupil of the objective lens.

[0013] The observation apparatus of the present invention may also be [7] "an observation apparatus according to any one of [1] to [6], which includes an input unit that receives input regarding information about the object to be observed and the position of the observation surface." In this case, it becomes possible to perform various controls on the observation apparatus (such as optical adjustments) in response to the input of the input unit.

[0014] The observation device of the present invention may also be [8] "an observation device according to any one of [1] to [7], which includes a mode switching unit that switches the observation mode of the observation surface between a transmission observation mode and a reflection observation mode, wherein in the transmission observation mode, the mode switching unit causes the imaging unit to detect the reflected light of the observation light that has passed through the irradiation unit and entered the interior of the object to be observed, which has passed through the observation surface, been emitted from the object to be observed, and passed through the irradiation unit again, and in the reflection observation mode, the imaging unit detects the reflected light of the observation light that has passed through the irradiation unit and entered the observation surface, which has been reflected by the observation surface acting as a reflective surface, which has passed through the irradiation unit again." In this case, it is possible to switch between observation in transmission observation mode and observation in reflection observation mode.

[0015] The observation apparatus of the present invention may also be [9] "the observation apparatus according to any one of [1] to [8], which includes a light source that emits light and an annular aperture through which the light emitted by the light source passes." In this case, the annular illumination apparatus can be configured using a light source and an annular aperture.

[0016] The observation apparatus of the present invention may also be

[10] "the observation apparatus according to any one of [1] to [8], wherein the annular illumination section includes a plurality of light-emitting diodes arranged in an annular shape." In this case, the annular illumination section can be configured using a plurality of light-emitting diodes.

[0017] The observation apparatus of the present invention may also be

[11] "the observation apparatus according to any one of [1] to [8], wherein the ring illumination section includes a light-emitting diode array having a plurality of light-emitting diodes arranged in a two-dimensional manner and whose illumination can be individually controlled, and in the light-emitting diode array, a plurality of the light-emitting diodes located in an annular region along the ring are illuminated." In this case, the diameter of the illumination pattern of the observation light can be easily changed.

[0018] The observation apparatus of the present invention may also be the observation apparatus described in

[11] , wherein at least one of the inner diameter and outer diameter of the annular region in the light-emitting diode array can be changed. In this case, it is possible to adjust the diameter of the illumination pattern of the reflected light of the observation light projected onto the pupil of the objective lens.

[0019] The observation apparatus of the present invention includes

[13] a mode switching unit that switches the observation mode of the observation surface between a real image observation mode and a mirror image observation mode, wherein in the real image observation mode, the observation surface is set at the position of the observation point on the object to be observed in the real image region that is located in front of the reflective surface of the observation light when viewed from the objective lens on the optical path of the reflected light of the observation light, and the reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, which has passed through the observation surface and exited the object to be observed and passed through the illumination unit again The observation device may be any of [1] to

[12] , wherein the reflected light is detected by the imaging unit, and in the mirror image observation mode, the observation surface is set at the position of the observation point on the object to be observed in the mirror image region that is located in front of the reflective surface of the observation light as seen from the objective lens on the optical path of the observation light, and the reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, and has passed through the observation surface, and has been emitted from the object to be observed and passed through the illumination unit again, is detected by the imaging unit. In this case, it is possible to switch between observation in real image observation mode and observation in mirror image observation mode.

[0020] The observation apparatus of the present invention may also be

[14] "an observation apparatus according to any one of [1] to

[13] , comprising a variable focus lens provided on the optical path from the objective lens to the imaging unit." In this case, the imaging unit can be adjusted by the variable focus lens so that it can image the observation surface.

[0021] The observation apparatus of the present invention may also be

[15] "an observation apparatus according to any one of [1] to

[14] , which is equipped with a moving mechanism for moving the imaging unit along the optical axis direction of the reflected light of the observation light." In this case, the moving mechanism can be used to adjust the imaging unit so that it can image the observation surface.

[0022] The observation method of the present disclosure is

[16] "An observation method for observing the observation surface of an object to be observed, comprising: an illumination step of irradiating the object to be observed with the observation light having an annular illumination pattern output from an annular illumination unit and an illumination unit including an objective lens with the observation surface as the focal plane; and an imaging step of imaging the observation surface, wherein the imaging step includes detecting reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, which is uniformly illuminated on the observation surface and emitted from the object to be observed and passed through the illumination unit again, and the illumination step includes adjusting the conjugate surface of the annular illumination unit to coincide with the pupil surface of the objective lens in the optical path of the reflected light of the observation light."

[0023] In this observation method, the observation surface can be made into the Fourier plane of the annular illumination by adjusting the conjugate surface of the annular illumination to coincide with the pupil surface of the objective lens in the optical path of the reflected light. This prevents the illumination pattern of the light projected onto the observation surface from remaining annular, making it possible to observe the observation surface properly.

[0024] This disclosure makes it possible to provide an observation device and observation method that can appropriately observe the observation surface of an object to be observed.

[0025] Figure 1 is a configuration diagram showing an observation device according to the first embodiment. Figure 2 is a diagram showing an example of the display in the GUI of Figure 1. Figure 3(a) is a configuration diagram showing the optical path of the observation light in the observation device of Figure 1. Figure 3(b) is a configuration diagram showing the optical path of the reflected light of the observation light in the observation device of Figure 1. Figure 4(a) is a configuration diagram showing the forward optical path and the return optical path folded back to form a single optical path in the observation device of Figure 1. Figure 5 is a schematic diagram illustrating the Fourier surface of the annular illumination section of Figure 1. Figure 6 is a flowchart showing an example of an observation method using the observation device of Figure 1. Figure 7 is a flowchart showing another example of an observation method using the observation device of Figure 1. Figure 8 is a configuration diagram showing the forward optical path and the return optical path folded back to form a single optical path in the observation device according to the second embodiment. Figure 9 is a configuration diagram showing the forward optical path and the return optical path folded back to form a single optical path in the observation device according to the third embodiment. Figure 10 is a configuration diagram showing the optical path of the reflected light of the observation light in the observation device according to the fourth embodiment. Figure 11(a) is a configuration diagram showing the forward and return optical paths as a single optical path when observing in transmission observation mode in the observation device of Figure 10. Figure 11(b) is a configuration diagram showing the forward and return optical paths as a single optical path when observing in reflection observation mode in the observation device of Figure 10. Figure 12 is another configuration diagram showing the optical path of the reflected light of the observation light in the observation device according to the fourth embodiment. Figure 13(a) is a configuration diagram showing the forward and return optical paths as a single optical path when observing in transmission observation mode in the observation device of Figure 12. Figure 13(b) is a configuration diagram showing the forward and return optical paths as a single optical path when observing in reflection observation mode in the observation device of Figure 12. Figure 14(a) is a configuration diagram of the observation device according to the fifth embodiment, showing the forward and return optical paths as a single optical path when observing in real-image observation mode. Figure 14(b) is a configuration diagram of the observation device of Figure 14(a), showing the forward and return optical paths as a single optical path when observing in mirror-image observation mode. Figure 15(a) is a schematic cross-sectional view of an object to be observed for illustrating the real-image observation mode. Figure 15(b) is a schematic cross-sectional view of an object to be observed for illustrating the mirror-image observation mode.Figure 16 is a configuration diagram showing an observation device according to the sixth embodiment. Figure 17(a) is a schematic diagram showing an annular illumination unit according to a modified example. Figure 17(b) is a schematic diagram showing an annular illumination unit according to another modified example.

[0026] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0027] <First Embodiment> [Configuration of Observation Device] As shown in Figure 1, the observation device 100 according to the first embodiment is an optical observation device for observing an observation location S of an object to be observed 10. The observation device 100 is used, for example, as a phase contrast microscope. The object to be observed 10 is, for example, a semiconductor device, but may also be other industrial samples formed from metal, glass, resin, liquid crystal, polymer compound, etc. The object to be observed 10 may also be a biological sample such as a cell or cell aggregate. The object to be observed 10 may be a single wafer or a so-called laminated wafer. The object to be observed 10 may be a substrate formed from at least one of silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), and silicon carbide (SiC). In this case, the substrate may contain a dopant. The object to be observed 10 has a surface 10a which is one main surface, and a back surface 10b which is the other main surface opposite to surface 10a.

[0028] The observation point S may be an internal scratch (subsurface damage) not visible from the surface 10a and back surface 10b of the object to be observed 10, a crystal defect, an internal defect accompanied by a change in refractive index, an internal crack, the bonding surface in a bonded wafer, a foreign object embedded in the bonding surface, a void in the bonding surface of a bonded wafer, a joint or bonding surface between glass and resin, a laser-processed surface inside a component made of glass, resin, or semiconductor, or an internal defect in a liquid crystal panel.

[0029] The observation device 100 observes an observation surface M set to correspond to an observation point S on the object to be observed 10. The observation device 100 comprises a light source unit 1, a half mirror 2, an illumination unit 3, an imaging lens 4, an imaging unit 5, a GUI (Graphical User Interface) 6, and a control unit 7.

[0030] The light source unit 1 includes an annular illumination unit 11 and a focus adjustment unit 12. The annular illumination unit 11 outputs observation light L1 having an annular illumination pattern. The annular illumination unit 11 includes a light source 14 that outputs light and an annular aperture 15 through which the light emitted from the light source 14 passes. The light source 14 may output visible light if the object to be observed 10 is transparent to visible light (for example, silicon and gallium arsenide). The light source 14 may output near-infrared light if the object to be observed 10 is transparent to near-infrared light. The annular aperture 15 is an aperture with an annular opening formed therein. The annular aperture 15 spatially filters the light emitted from the light source 14 and allows it to pass through as observation light L1. The annular shape is also referred to as ring-shaped, donut-shaped, etc. The light source unit 1 is housed in a housing K. The housing K is provided so as to be able to move closer to and further away from the object to be observed 10 by a drive unit (not shown), such as an actuator.

[0031] The focus adjustment unit 12 allows adjustment of the focus (focal length) of the light source unit 1. As will be described later, the focus adjustment unit 12 can adjust the focus of the light source unit 1 so that the conjugate surface of the annular illumination unit 11 coincides with the pupil surface of the objective lens 31 in the optical path of the reflected light L2. The focus adjustment unit 12 includes a condenser lens 16 and a variable focus lens 17. The condenser lens 16 guides the observation light L1 output from the annular illumination unit 11 toward the variable focus lens 17. Conjugate or conjugate relationship is the relationship between two points when light emitted from one of two points forms an image on the other. For example, when an image located on one surface forms an image on another surface, the other surface is said to be the conjugate surface of the first surface (in other words, the first surface is the conjugate surface of the other surface).

[0032] The variable focus lens 17 is a lens whose focal length can be adjusted. The variable focus lens 17 is a lens that changes its focal length according to, for example, the input current value. The variable focus lens 17 is a light guide lens that guides the observation light L1 that has passed through the condenser lens 16 toward the half mirror 2. The variable focus lens 17 is connected to the control unit 7, and its operation is controlled by the control unit 7. The type of variable focus lens 17 is not particularly limited, and various known variable focus lenses may be used.

[0033] The half-mirror 2 reflects the observation light L1 output from the light source 1 toward the illumination unit 3, and transmits the reflected light L2 of the observation light L1 toward the imaging lens 4. The half-mirror 2 is housed in the housing K.

[0034] The illumination unit 3 illuminates the object to be observed 10 from the surface 10a side with observation light L1 reflected by the half mirror 2. The illumination unit 3 is composed of a phase contrast objective lens. The illumination unit 3 includes an objective lens 31 with the observation surface M as its focal plane, and a phase difference plate 32 positioned on the half mirror 2 side of the objective lens 31. The illumination unit 3 is mounted on the housing K.

[0035] The objective lens 31 guides the observation light L1 toward the object to be observed 10 and the reflected light L2 toward the half mirror 2. The observation surface M is the focal plane of the objective lens 31. Here, optical adjustment (the housing K is moved) is performed so that the observation surface M becomes the focal plane of the objective lens 31. The phase difference plate 32 is formed in an annular shape with the optical axis as its central axis and includes a quarter-wave plate that shifts the phase of the light by 1 / 4λ. The phase difference plate 32 is also called a phase difference ring. In the illumination section 3, the parts other than the phase difference plate 32 are transparent to the observation light L1 and the reflected light L2. The phase difference plate 32 is positioned at the pupil plane of the objective lens 31.

[0036] The imaging lens 4 guides the reflected light L2 that has passed through the half mirror 2 toward the imaging unit 5. The imaging lens 4 is housed in the housing K. The imaging unit 5 images the observation surface M. For example, a camera is used as the imaging unit 5. When the observation surface M is the focal plane of the objective lens 31, the conjugate plane of the imaging unit 5 coincides with the observation surface M. The imaging unit 5 can detect the reflected light L2 of the observation light L1 that has passed through the illumination unit 3 and entered the interior of the object to be observed 10, which has passed through the observation surface M, been emitted from the object to be observed 10, and passed through the illumination unit 3 again (see Figures 3(a) and 3(b)). The imaging unit 5 is connected to the control unit 7 and outputs the imaging results to the control unit 7. The imaging unit 5 is housed in the housing K.

[0037] GUI 6 is, for example, a device that receives user input. GUI 6 receives input regarding information about the object to be observed 10 and the position of the observation surface M. GUI 6 constitutes the input unit. Examples of information about the object to be observed 10 include the type of material, thickness, and refractive index of the object to be observed 10. Examples of the position of the observation surface M include the depth of the observation surface M (distance from the surface 10a). When repeatedly observing while changing the observation surface M along the optical axis (so-called Z-scan, as described later), the position of the observation surface M includes the initial value, end value, and step size of the depth of the observation surface M. GUI 6 outputs the received input to the control unit 7. GUI 6 has, for example, a display that displays images. GUI 6 is controlled by the control unit 7 and displays the imaging results of the imaging unit 5 on the display. GUI 6 may be configured as, for example, a touch panel.

[0038] As illustrated in Figure 2, GUI 6 allows input by selecting the material type of the object to be observed 10. GUI 6 allows input of the thickness of the object to be observed 10. GUI 6 allows input of the depth of the observation surface M (distance from the surface 10a). GUI 6 allows display of the imaging results from the imaging unit 5.

[0039] The control unit 7 controls each part of the observation device 100. The control unit 7 is a computer consisting of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The control unit 7 can be configured as software in which, for example, a program stored in ROM is loaded onto RAM and executed by the CPU. The control unit 7 may also be configured as hardware, such as electronic circuits. The control unit 7 may consist of one device or multiple devices. If it consists of multiple devices, these are connected via a communication network such as the Internet or an intranet to logically construct a single control unit 7.

[0040] The control unit 7 controls the operation of the variable focus lens 17 based on the input received by the GUI 6. Specifically, the control unit 7 controls the focal length of the variable focus lens 17 based on the input received by the GUI 6, so that the conjugate surface of the annular illumination unit 11 matches the pupil plane of the objective lens 31 in the optical path of the reflected light L2. For example, when various inputs are made in the GUI 6 and the OK button is pressed, the control unit 7 calculates the propagation of light (observation light L1 and reflected light L2) from the annular aperture 15 to the phase difference plate 32 based on the input, calculates the focal value of the variable focus lens 17 to match the conjugate surface of the annular illumination unit 11 to the pupil plane of the objective lens 31 in the optical path of the reflected light L2, and provides this focal value to the variable focus lens 17. This automatically controls the focal length of the variable focus lens 17 so that the conjugate surface of the annular illumination unit 11 matches the pupil plane of the objective lens 31 in the optical path of the reflected light L2.

[0041] The control unit 7 controls the operation of the drive unit described above, which moves the housing K, based on the input received by the GUI 6. For example, when various inputs are made in the GUI 6 and the OK button is pressed, the control unit 7 controls the drive unit described above based on the input to automatically move the housing K along the optical axis direction and optically adjusts so that the focal plane of the objective lens 31 coincides with the observation plane M (that is, so that the conjugate plane of the imaging plane of the imaging unit 5 coincides with the observation plane M). The control unit 7 displays the imaging results of the imaging unit 5 on the GUI 6.

[0042] [Optical Path of Observation Device] Figure 3(a) is a diagram showing the optical path of the observation light L1 (hereinafter also referred to as the "forward optical path") in the observation device 100. Figure 3(b) is a diagram showing the optical path of the reflected light L2 of the observation light L1 (hereinafter also referred to as the "return optical path") in the observation device 100. Figure 4 is a diagram showing the observation device 100, with the forward optical path and the return optical path folded back to form a single optical path, symmetrically with respect to the back surface 10b of the object to be observed 10, which is the reflective surface. The state of the optical system in the figures shows the state during observation when observing the observation surface M.

[0043] As shown in Figures 3(a), 3(b), and 4, in the observation device 100, during observation, the control unit 7 controls the focal length of the variable focus lens 17 so that the conjugate plane of the annular illumination unit 11 coincides with the pupil plane of the objective lens 31 in the optical path (return path) of the reflected light L2. The control unit 7 moves the housing K along the optical axis so that the focal plane of the objective lens 31 coincides with the observation surface M (the conjugate plane of the imaging surface of the imaging unit 5 coincides with the observation surface M). In the observation device 100 during such observation, the observation direction, which is the direction from the imaging unit 5 toward the observation surface M, and the incident direction, which is the direction in which the reflected light L2 of the observation light L1 that has passed through the illumination unit 3 and entered the interior of the object to be observed 10 is incident on the observation surface M, are opposite each other. In other words, the observation direction and the incident direction are directions that face each other through the observation surface M.

[0044] Furthermore, the observation device 100 has the following relationships during observation: The Fourier plane of the annular illumination unit 11 coincides with the observation surface M. The Fourier plane of the annular illumination unit 11 coincides with the imaging surface of the imaging unit 5. The Fourier plane of the imaging surface of the imaging unit 5 coincides with the pupil plane of the objective lens 31 in the return path. The Fourier plane of the pupil plane of the objective lens 31 coincides with the observation surface M. For example, when an optical component has an incident side and an exit side, and there is a "first surface where parallel light input from the incident side is focused on the exit side" and a "second surface where parallel light input from the exit side is focused on the incident side," the first surface and the second surface are said to be in a Fourier plane relationship with each other. In the illustrated example, the diameter of the phase difference plate 32 and the diameter of the illumination pattern of reflected light L2 at the position of the phase difference plate 32 are the same. The diameter may be at least one of the outer diameter, inner diameter, and center diameter (the same applies to the following diameters).

[0045] When the Fourier plane of the annular illumination unit 11 coincides with the observation surface M, as shown in FIG. 5, regarding the annular illumination pattern PS of the light (observation light L1 or reflected light L2) transmitted through the objective lens 31, the following can be said. That is, the illumination pattern PS changes its shape as the position on the optical axis changes from the upstream side (upper side in the drawing) to the downstream side (lower side in the drawing) of the light, becomes uniform illumination on the observation surface M, and then returns to an annular shape again. Therefore, the coincidence of the Fourier plane of the annular illumination unit 11 and the observation surface M may mean that the light converges on the observation surface M, or instead of or in addition to this, the light becomes uniform illumination (the illumination pattern PS is uniform) on the observation surface M.

[0046] Returning to FIGS. 3(a), 3(b) and FIG. 4, in such an observation apparatus 100, when observing the observation surface M of the observation object 10, light is emitted from the light source 14, and the light is spatially filtered by the annular aperture 15 and output as the observation light L1. The observation light L1 passes through the condenser lens 16 and the focus variable lens 17, is reflected by the half mirror 2, and enters the irradiation unit 3. The observation light L1 passes through the irradiation unit 3 (the phase difference plate 32 and the objective lens 31), enters the inside of the observation object 10 from the surface 10a, and is reflected with the back surface 10b as the reflection surface.

[0047] The reflected light L2 becomes uniform illumination on the observation surface M and passes through the observation surface M, and is emitted from the surface 10a of the observation object 10. The reflected light L2 that has passed through the observation surface M includes direct light that travels straight through the inside of the observation location S and diffracted light that is diffracted by the observation location S and travels bent. Since the diffraction phenomenon occurs at a site with a refractive index difference, the diffracted light includes the shape information of the observation location S and the like.

[0048] The reflected light L2 emitted from the observation object 10 passes through the irradiation unit 3 again. Here, in the irradiation unit 3, the direct light of the reflected light L2 is guided by the objective lens 31 and passes through the retardation plate 32, so that the phase is shifted by 1 / 4λ and the brightness is weakened at the same time. On the other hand, most of the diffracted light of the reflected light L2 passes through the part (transparent part) other than the retardation plate 32, so the phase and brightness do not change. Then, the reflected light L2 that has passed through the irradiation unit 3 again passes through the half mirror 2, passes through the imaging lens 4, and reaches the imaging surface of the imaging unit 5. Thereby, the phase contrast image of the observation surface M with the contrast of light and dark due to the direct light and diffracted light of the reflected light L2 is detected by the imaging unit 5.

[0049] [Observation method] Next, an example of an observation method for observing the observation location S of the observation object 10 using the observation apparatus 100 will be described while referring to the flowchart of FIG. 6.

[0050] First, the depth of the observation surface M corresponding to the observation location S and the information (type and thickness) of the observation object 10 are input via the GUI 6 (step S1). The information of the observation object 10 includes, for example, the type and thickness of the material of the observation object 10. The control unit 7 moves the housing K along the optical axis direction so that the focal plane of the objective lens 31 is positioned at the depth of the observation surface M input in step S1 (step S2). Thereby, the objective lens 31 is focused on the observation surface M, the conjugate surface of the imaging surface of the imaging unit 5 coincides with the observation surface M, and the observation surface M can be imaged by the imaging unit 5.

[0051] The control unit 7 calculates the focal value of the variable focus lens 17 based on the information input in step S1, when the conjugate surface of the annular aperture 15 of the annular illumination unit 11 coincides with the pupil surface of the objective lens 31 in the return optical path (step S3). The control unit 7 adjusts the variable focus lens 17 with the focal value calculated in step S3, thereby aligning the conjugate surface of the annular aperture 15 with the pupil surface (phase difference plate 32) of the objective lens 31 in the return optical path (step S4). Then, the annular illumination unit 11 outputs observation light L1, the illumination unit 3 illuminates the object to be observed 10 with the observation light L1, the imaging unit 5 captures a phase contrast image, and the imaging result is stored in the control unit 7, etc. (step S5). In the above, steps S2 to S5 constitute the imaging process, and step S5 constitutes the illumination process. According to the above, it becomes possible to appropriately observe the observation surface M with uniform illumination.

[0052] Furthermore, in the observation method described above, when repeatedly observing while changing the observation surface M along the optical axis (so-called Z-scan), as shown in Figure 7, for example, first, the initial value, end value, and step size of the depth of the observation surface M are input via GUI 6 (step S11). Also, information about the object to be observed 10 is input via GUI 6 (step S12).

[0053] The control unit 7 sets the observation surface M to a position corresponding to the initial value of the depth of the observation surface M (step S13). The control unit 7 moves the housing K along the optical axis so that the focal plane of the objective lens 31 is positioned at the current depth of the observation surface M (step S14). As a result, the objective lens 31 focuses on the observation surface M, the conjugate plane of the imaging surface of the imaging unit 5 coincides with the observation surface M, and the imaging unit 5 becomes capable of imaging the observation surface M.

[0054] The control unit 7 calculates the focal value of the variable focus lens 17 when the conjugate surface of the annular aperture 15 of the annular illumination unit 11 coincides with the pupil surface of the objective lens 31 in the return optical path, based on the information input in step S12 and the current depth of the observation surface M (step S15). The variable focus lens 17 is adjusted with the focal value calculated in step S15, thereby aligning the conjugate surface of the annular aperture 15 with the pupil surface (phase difference plate 32) of the objective lens 31 in the return optical path (step S16). Observation light L1 is output from the annular illumination unit 11, the illumination unit 3 irradiates the object to be observed 10 with the observation light L1, the imaging unit 5 captures a phase contrast image, and the imaging result is stored in the control unit 7, etc. (step S17).

[0055] In order to calculate the focal value of the variable focus lens 17 based on the information entered in step S12 and the current depth of the observation surface M, the focal value of the variable focus lens 17 may be calculated by calculation based on a geometric optics formula, or it may be calculated by fitting based on a calibration curve that relates the observation depth and the focal value of the variable focus lens 17 under the conditions of each observation object 10. If a calibration curve is to be obtained in advance, for example, for a calibration sample in which there are multiple characteristic structures at a particular depth, the focal value of the variable focus lens 17 can be experimentally determined sequentially at the position of the observation surface M corresponding to the depth of each characteristic structure, when the conjugate surface of the annular aperture 15 of the annular illumination unit 11 coincides with the pupil surface of the objective lens 31 in the return path, and a fitting curve for discrete data that correlates the obtained observation depth and focal value can be calculated.

[0056] Step S18 determines whether the current depth of the observation surface M corresponds to the end value entered in step S1. If the answer in step S18 is YES, the observation is terminated. If the answer in step S18 is NO, the current depth of the observation surface M is changed by the step width entered in step S1, and the process returns to step S14. In the above, steps S14 to S17 constitute the imaging process, and step S17 constitutes the irradiation process.

[0057] [Effects] In the observation device 100 and the observation method using it described above, the conjugate plane of the annular illumination unit 11 is adjusted to coincide with the pupil plane of the objective lens 31 in the return path of the optical path. This makes the observation surface M the Fourier plane of the annular illumination unit 11, preventing the illumination pattern of the reflected light L2 projected onto the observation surface M from remaining annular, and allowing the reflected light L2 to be uniformly illuminated or focused on the observation surface M. Therefore, it becomes possible to observe the observation surface M appropriately. In addition, at positions that are defocused in the direction of approaching or moving away from the objective lens 31 relative to the observation surface M, the illumination pattern becomes annular, so the proportion of diffracted light from these positions that enters the objective lens 31 is smaller than the proportion of diffracted light from the observation surface M, thus providing a sectioning effect in the optical axis direction.

[0058] In the observation device 100, the illumination unit 3 is composed of a phase-contrast objective lens. In this case, for example, a one-sided incidence transmission phase-contrast microscope can be realized in which the observation light L1 is incident from one side of the object to be observed 10. Being able to perform internal observation with such a one-sided incidence optical system has practical advantages, as it reduces the occupied volume of the observation device 100 and reduces the number of parts.

[0059] In the observation device 100, the observation direction from the imaging unit 5 toward the observation surface M and the incident direction from which the reflected light L2 enters the observation surface M are opposite (see Figure 4). In this case, the observation surface M can be observed by making the observation direction and the incident direction opposite. By making the observation direction and the incident direction opposite, transmission information on the observation surface M of the object to be observed 10 can be obtained, and thus information on the light that has passed through the object to be observed 10 can be obtained.

[0060] In the observation device 100, the focus adjustment unit 12 includes a variable focus lens 17. In this case, the focus of the light source unit 1 can be adjusted at high speed.

[0061] The observation device 100 is equipped with a GUI 6. The GUI 6 receives input regarding information about the object to be observed 10 and the position of the observation surface M. In this case, various controls (such as optical adjustments) of the observation device 100 can be performed according to the input received by the GUI 6.

[0062] In the observation device 100, the annular illumination unit 11 includes a light source 14 and an annular aperture 15. In this case, the annular illumination unit 11 can be configured using the light source 14 and the annular aperture 15.

[0063] Incidentally, in this embodiment, the illumination unit 3 does not necessarily have a phase difference plate 32. In this case, the observation device 100 functions as a dark-field microscope. In this case, similar to the example shown in Figure 5, the illumination pattern PS changes shape as the position on the optical axis changes from the upstream side (upper side in the figure) to the downstream side (lower side in the figure), resulting in uniform illumination on the observation surface M, and then returning to an annular shape. At positions defocused in the direction of approaching or moving away from the objective lens 31 with respect to the observation surface M, the illumination pattern PS becomes annular, so the proportion of diffracted light from these positions that enters the objective lens 31 is smaller than that of diffracted light from the observation surface M, thus obtaining a sectioning effect in the optical axis direction. Furthermore, because the component of straight-traveling light passing through the center of the optical axis is small in the observation light L1 and reflected light L2, the background light component of the image captured by the imaging unit 5 is reduced, and an image with a high signal-to-noise ratio can be obtained according to the principle of a dark-field microscope.

[0064] <Second Embodiment> Next, a second embodiment will be described. In this description, the differences from the first embodiment will be explained, and redundant explanations will be omitted.

[0065] As shown in Figure 8, the observation device 200 according to the second embodiment differs from the first embodiment in that the focus adjustment unit 12 is equipped with a variable focus lens 216 instead of a condenser lens 16 (see Figure 4).

[0066] The variable focus lens 216 is a different variable focus lens from the variable focus lens 17. The variable focus lens 216 is a lens whose focal length can be adjusted. The variable focus lens 216 is a lens that changes its focal length according to, for example, the input current value. The variable focus lens 216 guides the observation light L1 output from the annular illumination unit 11 toward the variable focus lens 17. The variable focus lens 216 is connected to the control unit 7, and its operation is controlled by the control unit 7. The type of variable focus lens 216 is not particularly limited, and various known variable focus lenses may be used.

[0067] As described above, the observation device 200 and the observation method using it also achieve the above-mentioned effect of being able to properly observe the observation surface M. Furthermore, in the observation device 200, the focus adjustment unit 12 includes a variable focus lens 216. In this case, by adjusting the focal length of the variable focus lens 216 in addition to the variable focus lens 17, it is possible to adjust the diameter of the illumination pattern of the reflected light L2 projected onto the pupil surface of the objective lens 31. As a result, the diameter of the illumination pattern of the reflected light L2 projected onto the pupil surface of the objective lens 31 can be adjusted to be the same as the diameter of the phase difference plate 32.

[0068] <Third Embodiment> Next, a third embodiment will be described. In this description, the differences from the first embodiment will be explained, and redundant explanations will be omitted.

[0069] As shown in Figure 9, the observation device 300 according to the third embodiment differs from the first embodiment in that the focus adjustment unit 12 includes an electric stage 316, which is a moving mechanism that moves the annular aperture 15 along the optical axis direction of the observation light L1. The electric stage 316 is connected to the control unit 7, and the amount of movement of the annular aperture 15 is controlled by the control unit 7.

[0070] As described above, the observation device 300 and the observation method using it also achieve the above-mentioned effect of being able to properly observe the observation surface M. Furthermore, in the observation device 300, the focus adjustment unit 12 further includes an electric stage 316. In this case, by appropriately moving the annular aperture 15 with the electric stage 316, it is possible to adjust the diameter of the illumination pattern of the reflected light L2 projected onto the pupil surface of the objective lens 31. As a result, the diameter of the illumination pattern of the reflected light L2 projected onto the pupil surface of the objective lens 31 can be adjusted to be the same as the diameter of the phase difference plate 32. In this case, the moving mechanism moves the annular aperture 15 as an optical element included in the light source unit 1, but other optical elements included in the light source unit 1 may be moved instead or in addition to this.

[0071] <Fourth Embodiment> Next, a fourth embodiment will be described. In this description, the differences from the first embodiment will be explained, and redundant explanations will be omitted.

[0072] Figure 10 is a configuration diagram showing the return optical path in the observation device 400 according to the fourth embodiment. Figure 11(a) is a configuration diagram showing the forward optical path and the return optical path as a single optical path when observing in transmission observation mode in the observation device 400. Figure 11(b) is a configuration diagram showing the forward optical path and the return optical path as a single optical path when observing in reflection observation mode in the observation device 400. Figure 11(a) shows the observation device 400 symmetrical with respect to the back surface 10b of the object to be observed 10, which is the reflective surface, and Figure 11(b) shows the observation device 400 symmetrical with respect to the front surface 10a of the object to be observed 10, which is the reflective surface.

[0073] As shown in Figure 10, the observation device 400 according to the fourth embodiment differs from the first embodiment in that the control unit 7 has a mode switching unit 416 as a functional configuration. The mode switching unit 416 switches the observation mode of the observation surface M between transmission observation mode and reflection observation mode. The switching of the observation mode by the mode switching unit 416 can be selected and executed by the user, for example, via the GUI 6. In the illustrated example, the observation surface M is set to the surface 10a of the object to be observed 10.

[0074] In the transmission observation mode, the mode switching unit 416 causes the imaging unit 5 to detect the reflected light L2 of the observation light L1 that has passed through the irradiation unit 3 and entered the interior of the object to be observed 10, which has passed through the observation surface M, been emitted from the object to be observed 10, and passed through the irradiation unit 3 again. For example, the mode switching unit 416 performs optical adjustment of the observation device 400 to set the observation mode to transmission observation mode so that such reflected light L2 is detected by the imaging unit 5.

[0075] In reflection observation mode, the mode switching unit 416 causes the imaging unit 5 to detect the reflected light L2, which is the observation light L1 that has passed through the illumination unit 3 and been incident on the observation surface M, and which has been reflected by the observation surface M acting as a reflective surface, and which has passed through the illumination unit 3 again. For example, the mode switching unit 416 performs optical adjustment of the observation device 400 to set the observation mode to reflection observation mode so that such reflected light L2 is detected by the imaging unit 5.

[0076] As shown in Figure 11(a), in transmission observation mode, when observing the observation surface M of the object to be observed 10, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3, enters the interior of the object to be observed 10 from the surface 10a, and is reflected by the back surface 10b which acts as a reflective surface. The reflected light L2 provides uniform illumination on the observation surface M and passes through the observation surface M, and is emitted from the surface 10a of the object to be observed 10. The reflected light L2 emitted from the object to be observed 10 passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4, and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in transmission observation mode is detected by the imaging unit 5.

[0077] As shown in Figure 11(b), in reflection observation mode, when observing the observation surface M of the object to be observed 10, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3, and is uniformly illuminated and reflected at the surface 10a, which is the observation surface M. The reflected light L2 passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4 and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in reflection observation mode is detected by the imaging unit 5.

[0078] As described above, the observation device 400 and the observation method using it also achieve the above-mentioned effect of being able to properly observe the observation surface M. Furthermore, the observation device 400 has a mode switching unit 416 in the control unit 7, which switches the observation mode of the observation surface M between transmission observation mode and reflection observation mode. In this case, it is possible to switch between observation using transmission observation mode and observation using reflection observation mode with a single device. This is useful when it is necessary to distinguish between foreign matter on the surface 10a of the object to be observed and foreign matter around the surface 10a (for example, directly below the surface 10a).

[0079] Figure 12 is another configuration diagram showing the return optical path in the observation device 400. Figure 13(a) is another configuration diagram showing the forward optical path and the return optical path as a single optical path when observing in transmission observation mode in the observation device 400. Figure 13(b) is another configuration diagram showing the forward optical path and the return optical path as a single optical path when observing in reflection observation mode in the observation device 400. Figure 13(a) shows the observation device 400 symmetrical with respect to the back surface 410b of the observation object 410, which is the reflective surface, and Figure 13(b) shows the observation device 400 symmetrical with respect to the bonded surface 410m, which is the reflective surface.

[0080] In this embodiment, as shown in Figure 12, the bonding surface 410m of the object to be observed, which is a bonded wafer, can also be observed as the observation surface M. The object to be observed 410 consists of a substantially flat first wafer 411 and a substantially flat second wafer 412, which are stacked with a bonding surface 410m in between. The object to be observed 410 has a main surface 410a of the first wafer 411 and a main surface 410b of the second wafer 412, which is the back surface opposite to the surface 10a. The observation surface M is set to the bonding surface 410m of the object to be observed 410.

[0081] As shown in Figure 13(a), in transmission observation mode, when observing the observation surface M of the object to be observed 410, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3, enters the interior of the object to be observed 410 from the surface 410a, and is reflected by the back surface 410b which acts as a reflective surface. The reflected light L2 provides uniform illumination on the observation surface M and passes through the observation surface M, and is emitted from the surface 10a of the object to be observed 10. The reflected light L2 emitted from the object to be observed 10 passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4, and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in transmission observation mode is detected by the imaging unit 5.

[0082] As shown in Figure 13(b), in reflection observation mode, when observing the observation surface M of the object to be observed 410, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3 and incident on the interior of the first wafer 411 from the surface 410a, and is uniformly illuminated and reflected on the bonded surface 410m, which is the observation surface M. The reflected light L2 is emitted from the surface 10a of the object to be observed 10, passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4 and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in reflection observation mode is detected by the imaging unit 5. Even in this modified example, the above-mentioned effect of being able to properly observe the observation surface M is achieved.

[0083] Furthermore, when observing observation locations S as voids present on the bonded surface 410m and its vicinity in an observation object 410 which is a bonded wafer, if the bonded surface 410m is properly bonded, the amount of reflected light L2 from the bonded surface 410m becomes very small, making it very difficult to focus on the bonded surface 410m. Therefore, in this case, since almost no reflected light L2 may be obtained in the reflection observation mode, observation in the transmission observation mode is effective. On the other hand, if a reflective surface such as metal exists on the bonded surface 410m or its back surface 410b, the observation light L1 does not pass through, so observation in the transmission observation mode is effective. Therefore, this embodiment and its modifications, which allow switching between observation in transmission observation mode and observation in reflection observation mode with a single device, are particularly useful when observing observation locations S as voids inside a bonded wafer.

[0084] <Fifth Embodiment> Next, the fifth embodiment will be described. In describing this embodiment, the differences from the fourth embodiment described above will be explained, and redundant explanations will be omitted.

[0085] Figure 14(a) is a configuration diagram of the observation device 500 according to the fifth embodiment, showing the forward optical path and the return optical path folded back together as a single optical path during observation in real image observation mode. Figure 14(b) is a configuration diagram of the observation device 500, showing the forward optical path and the return optical path folded back together as a single optical path during observation in mirror image observation mode. Figures 14(a) and 14(b) show the observation device 500 symmetrical with respect to the back surface 10b of the object to be observed 10, which is a reflective surface.

[0086] As shown in Figures 14(a) and 14(b), the observation device 500 differs from the fourth embodiment in that the mode switching unit 416 switches the observation mode of the observation surface M between the real image observation mode and the mirror image observation mode.

[0087] As shown in Figure 14(a), in real-image observation mode, the mode switching unit 416 sets the observation surface M at the position of the observation point S on the object 10R in the real-image region, which is located in front of the back surface 10b, the reflective surface of the observation light L1, as seen from the objective lens 31 on the optical path of the reflected light L2. In real-image observation mode, the mode switching unit 416 causes the imaging unit 5 to detect the reflected light L2 of the observation light L1 that has passed through the illumination unit 3 and entered the interior of the object 10, and which has passed through the observation surface M, been emitted from the object 10, and passed through the illumination unit 3 again. For example, the mode switching unit 416 performs optical adjustment of the observation device 400 to set the observation mode to real-image observation mode so that such reflected light L2 is detected by the imaging unit 5.

[0088] As shown in Figure 14(b), in mirror image observation mode, the mode switching unit 416 sets the observation surface M at the position of the observation point S on the object 10M in the mirror image region, which is located in front of the back surface 10b, which is the reflective surface of the observation light L1, as seen from the objective lens 31 on the optical path of the observation light L1. In mirror image observation mode, the mode switching unit 416 causes the imaging unit 5 to detect the reflected light L2 of the observation light L1 that has passed through the illumination unit 3 and entered the interior of the object 10, and has passed through the observation surface M, and has been emitted from the object 10 and passed through the illumination unit 3 again. For example, the mode switching unit 416 performs optical adjustment of the observation device 400 to set the observation mode to mirror image observation mode so that such reflected light L2 is detected by the imaging unit 5.

[0089] As shown in Figure 14(a), in real-image observation mode, when observing the observation surface M of the object to be observed 10, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable-focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3, enters the interior of the object to be observed 10 from the surface 10a, and is reflected by the back surface 10b which acts as a reflective surface. The reflected light L2 provides uniform illumination on the observation surface M (i.e., the observation surface M of the object to be observed 10R in the real-image region), passes through the observation surface M, and is emitted from the surface 10a of the object to be observed 10. The reflected light L2 emitted from the object to be observed 10 passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4, and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in real-image observation mode is detected by the imaging unit 5.

[0090] As shown in Figure 14(b), in mirror image observation mode, when observing the observation surface M of the object to be observed 10, the light emitted from the light source 14 is spatially filtered by the annular aperture 15 and output as observation light L1. The observation light L1 passes through the condenser lens 16 and the variable focus lens 17, is reflected by the half mirror 2 and incident on the illumination unit 3, passes through the illumination unit 3 and incident on the interior of the object to be observed 10 from the surface 10a. The observation light L1 provides uniform illumination on the observation surface M (i.e., the observation surface M of the object to be observed 10M in the mirror image region), passes through the observation surface M, and is reflected by the back surface 10b which acts as a reflective surface. The reflected light L2 is emitted from the surface 10a of the object to be observed 10, passes through the illumination unit 3 again, passes through the half mirror 2, passes through the imaging lens 4 and reaches the imaging surface of the imaging unit 5. As a result, the phase contrast image of the observation surface M in mirror image observation mode is detected by the imaging unit 5.

[0091] As described above, the observation device 500 and the observation method using it achieve the above-mentioned effects, which include the ability to appropriately observe the observation surface M. Furthermore, the observation device 500 allows for switching between observing the observation surface M in real-image observation mode and observing the observation surface M in mirror-image observation mode using the mode switching unit 416. This provides the following effects.

[0092] In other words, for example, as shown in Figure 15(a), if the observation point S on the object to be observed 10 includes a crack C extending toward the back surface 10b, when observing the observation point S of the object to be observed 10R in the real image region in real image observation mode, the tip of the crack C may be obstructed by the structure between the crack C and the objective lens 31, making it impossible to properly image the tip of the crack C. Therefore, in this case, by switching the observation mode to the mirror image observation mode using the mode switching unit 416 and imaging the observation point S of the object to be observed 10M in the mirror image region (imaging the structure on the opposite side that is reflected by the back surface 10b), the tip of the crack C can be properly imaged because there is no obstructing structure between the crack C and the objective lens 31. This embodiment can also be said to be particularly effective when observing a crack (so-called lower crack) extending from the modified region to the back surface side in an object to be observed 10 in which a modified region has been formed inside. Furthermore, if images are taken of a sample with the same structure using both the real-image observation mode and the virtual-image observation mode, two types of images will be obtained at the same depth position within the sample. GUI6 may therefore be equipped with a function to improve user convenience by displaying these images superimposed.

[0093] <Sixth Embodiment> Next, the sixth embodiment will be described. In describing this embodiment, the differences from the first embodiment described above will be explained, and redundant explanations will be omitted.

[0094] As shown in Figure 16, the observation device 600 according to the sixth embodiment differs from the first embodiment in that it is equipped with a variable focus lens 604 instead of the imaging lens 4 (see Figure 1). The variable focus lens 604 is provided on the optical path from the objective lens 31 to the imaging unit 5. The variable focus lens 604 is a lens whose focal length can be adjusted. The variable focus lens 604 is a lens that changes its focal length according to, for example, the input current value. The variable focus lens 604 guides the reflected light L2 that has passed through the half mirror 2 toward the imaging unit 5. The variable focus lens 604 is connected to the control unit 7, and its operation is controlled by the control unit 7. The type of variable focus lens 17 is not particularly limited, and various known variable focus lenses may be used. The variable focus lens 604 is housed in the housing K.

[0095] The control unit 7 controls the operation of the variable focus lens 604 based on the input received by the GUI 6. For example, the control unit 7 changes the focal length of the variable focus lens 604 based on the input received by the GUI 6 and optically adjusts the focal plane of the objective lens 31 so that it becomes the observation plane M (that is, so that the conjugate plane of the imaging plane of the imaging unit 5 becomes the observation plane M).

[0096] As described above, the observation device 600 and the observation method using it achieve the above-mentioned effects of being able to properly observe the observation surface M. Furthermore, the observation device 600 is equipped with a variable focus lens 604, and the imaging unit 5 can be adjusted so that it can image the observation surface M using the variable focus lens 604. This reduces the need to move the various optical systems (housing K, etc.) of the observation device 600, enabling high-speed and accurate observation. In addition, the lifespan of the number of reciprocating movements of the mechanical stage that moves the various optical systems of the observation device 600 is generally on the order of several million. In contrast, it is possible to use a variable focus lens 604 with a lifespan of more than 100 million focus changes. Therefore, the observation device 600 and the observation method using it are also useful from the viewpoint of improving the reliability of the observation device 600.

[0097] <Modifications> The embodiments described above are not limited to the above embodiments and modifications.

[0098] In the above embodiment, the annular illumination unit 11 is configured to include a light source 14 and an annular aperture 15. However, the configuration of the annular illumination unit 11 is not particularly limited, and various configurations are acceptable as long as they can output observation light L1 having an annular illumination pattern. For example, as shown in Figure 17(a), the annular illumination unit 11 may include a plurality of light-emitting diodes 74 arranged in an annular shape. The type of light-emitting diodes 74 is not particularly limited. With such a configuration, the annular illumination unit 11 can be configured using a plurality of light-emitting diodes 74.

[0099] For example, as shown in Figure 17(b), the annular illumination unit 11 may also include a light-emitting diode array 81 having a plurality of light-emitting diodes 82 arranged in a two-dimensional manner, each of which can be individually controlled to either be lit or not. The type of light-emitting diodes 82 is not particularly limited. In this case, in the light-emitting diode array 81, a plurality of light-emitting diodes 82 located in the annular region 83 are lit. With such a configuration, the diameter of the illumination pattern of the observation light L1 can be easily changed. In this case, in the light-emitting diode array 81, at least one of the inner diameter and outer diameter of the annular region 83 may be changeable. This makes it possible to adjust the diameter of the illumination pattern of the reflected light L2 projected onto the pupil of the objective lens 31 to be the same as the diameter of the phase difference plate 32.

[0100] In the above embodiment, the imaging unit 5 may be provided with a moving mechanism that moves it along the optical axis direction of the reflected light L2. In this case, for example, the control unit 7 can move the moving mechanism based on the input received by the GUI 6, and optical adjustment can be made so that the imaging unit 5 can image the observation surface M. This reduces the need to move various optical systems of the observation device, enabling highly accurate observation.

[0101] In the above embodiment, the focus adjustment unit 12 may be equipped with a moving mechanism for moving the light source 14 in place of or in addition to the variable focus lens 17, or it may be equipped with a spatial light modulator that modulates the input light and outputs the observation light L1. In the above first embodiment, the variable focus lens 17 may be a light guide lens (fixed focus lens) that does not have a variable focus function, and the condenser lens 16, which is a fixed focus lens, may be a variable focus lens. In this case as well, it is possible to obtain the focal length adjustment effect described above.

[0102] The components in the above embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. Furthermore, the components in the above embodiments and modifications can be arbitrarily applied to the components in other embodiments or modifications. In the above, the term "identical" includes not only complete identicalness but also approximate identicalness that allows for measurement errors, manufacturing errors, etc. In the above, the term "identical" includes not only complete identicalness but also approximate identicalness that allows for measurement errors, manufacturing errors, etc.

[0103] 1...Light source unit, 31...Objective lens, 3...Irradiation unit, 5...Imaging unit, 6...GUI (Input unit), 10, 410...Object to be observed, 10M...Object to be observed in the mirror image area, 10R...Object to be observed in the real image area, 11...Annular illumination unit, 12...Focus adjustment unit, 14...Light source, 15...Annular aperture (optical element), 17...Variable focus lens, 74...Light-emitting diode, 81...Light-emitting diode array, 82...Light-emitting diode, 83...Annular area, 100, 200, 300, 400, 500, 600...Observation device, 216...Variable focus lens (other variable focus lenses), 316...Motorized stage (movement mechanism), 416...Mode switching unit, 604...Variable focus lens, L1...Observation light, L2...Reflected light, M...Observation surface, PS...Illumination pattern, S...Observation location.

Claims

1. An observation device for observing the observation surface of an object to be observed, comprising: a light source unit including an annular illumination unit that outputs observation light having an annular illumination pattern; an illumination unit including an objective lens with the observation surface as its focal plane, which irradiates the object to be observed with the observation light; and an imaging unit that images the observation surface, wherein the imaging unit is capable of detecting reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, which has passed through the observation surface, been emitted from the object to be observed, and passed through the illumination unit again; and the light source unit includes a focus adjustment unit capable of adjusting the focus of the light source unit so that the conjugate surface of the annular illumination unit coincides with the pupil plane of the objective lens in the optical path of the reflected light of the observation light.

2. The observation apparatus according to claim 1, wherein the illumination unit is composed of a phase contrast objective lens.

3. The observation apparatus according to claim 1 or 2, wherein the observation direction, which is the direction from the imaging unit toward the observation surface, and the incident direction, in which the reflected light of the observation light that has passed through the irradiation unit and entered the interior of the object to be observed enters the observation surface, are opposite each other.

4. The observation apparatus according to any one of claims 1 to 3, wherein the focus adjustment unit includes a variable focus lens.

5. The observation apparatus according to claim 4, wherein the focus adjustment unit further includes another variable focus lens separate from the variable focus lens.

6. The observation apparatus according to claim 4, wherein the focus adjustment unit includes a movement mechanism for moving the optical elements included in the light source unit in the optical axis direction of the observation light.

7. An observation device according to any one of claims 1 to 6, comprising an input unit for receiving input regarding information about the object to be observed and the position of the observation surface.

8. An observation device according to any one of claims 1 to 7, comprising a mode switching unit for switching the observation mode of the observation surface between a transmission observation mode and a reflection observation mode, wherein the mode switching unit, in the transmission observation mode, causes the imaging unit to detect the reflected light of the observation light that has passed through the irradiation unit and entered the interior of the object to be observed, which has passed through the observation surface, been emitted from the object to be observed, and passed through the irradiation unit again, and in the reflection observation mode, causes the imaging unit to detect the reflected light of the observation light that has passed through the irradiation unit and entered the observation surface, which has been reflected by the observation surface acting as a reflective surface, which has passed through the irradiation unit again.

9. The observation apparatus according to any one of claims 1 to 8, wherein the annular illumination section includes a light source that emits light and an annular aperture through which the light emitted by the light source passes.

10. The observation apparatus according to any one of claims 1 to 8, wherein the ring illumination section includes a plurality of light-emitting diodes arranged in a ring shape.

11. The observation device according to any one of claims 1 to 8, wherein the ring illumination section includes a light-emitting diode array having a plurality of light-emitting diodes arranged in a two-dimensional manner and whose illumination can be individually controlled, and in the light-emitting diode array, a plurality of the light-emitting diodes located in an annular region along the ring are illuminated.

12. The observation apparatus according to claim 11, wherein at least one of the inner diameter and outer diameter of the annular region in the light-emitting diode array is changeable.

13. The observation surface is provided with a mode switching unit that switches the observation mode between a real image observation mode and a mirror image observation mode, wherein in the real image observation mode, the observation surface is set at the position of the observation point on the object to be observed in the real image region that is located in front of the reflective surface of the observation light as seen from the objective lens on the optical path of the reflected light of the observation light, and the imaging unit detects the reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, and has passed through the observation surface and been emitted from the object to be observed and passed through the illumination unit again, wherein in the mirror image observation mode, the observation surface is set at the position of the observation point on the object to be observed in the mirror image region that is located in front of the reflective surface of the observation light as seen from the objective lens on the optical path of the observation light, An observation apparatus according to any one of claims 1 to 12, wherein the imaging unit detects the reflected light of the observation light that has passed through the irradiation unit and entered the interior of the object to be observed, and has passed through the observation surface, and has been emitted from the object to be observed and passed through the irradiation unit again.

14. An observation apparatus according to any one of claims 1 to 13, comprising a variable-focus lens provided in the optical path from the objective lens to the imaging unit.

15. An observation apparatus according to any one of claims 1 to 14, comprising a moving mechanism for moving the imaging unit along the optical axis direction of the reflected light of the observation light.

16. An observation method for observing the observation surface of an object to be observed, comprising: an illumination step of irradiating the object to be observed with observation light having an annular illumination pattern output from an annular illumination unit and an illumination unit including an objective lens with the observation surface as the focal plane; and an imaging step of imaging the observation surface, wherein the imaging step includes detecting reflected light of the observation light that has passed through the illumination unit and entered the interior of the object to be observed, which is uniformly illuminated on the observation surface and is emitted from the object to be observed and passes through the illumination unit again, and the illumination step includes adjusting the conjugate surface of the annular illumination unit to coincide with the pupil surface of the objective lens in the optical path of the reflected light of the observation light.

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