Estimation device, estimation system, estimation method, and recording medium

Abstract

Provided is an estimation device whereby a three-dimensional optical characteristic of an object can be acquired with high precision and high spatial resolution even when the object has a large thickness.　The estimation device comprises memory and a processor, and the memory stores first wavefront information and second wavefront information. The first wavefront information is information of a wavefront acquired on the basis of first illumination light transmitted through an object, and the second wavefront information is information of a wavefront acquired on the basis of second illumination light transmitted through the object. The wavelength of maximum intensity in the second illumination light is positioned further toward the short wavelength side than the wavelength of maximum intensity in the first illumination light. The processor executes estimation processing for estimating a three-dimensional optical characteristic of the object, and the three-dimensional optical characteristic is a refractive index distribution or an absorptivity distribution. The estimation processing uses both the first wavefront information and the second wavefront information.

Description

[Technical field]

[0001] The present invention relates to an estimation device, an estimation system, an estimation method, and a recording medium. [Background technology]

[0002] There is a reconstruction method that reproduces an actual object with an object model on a computer. In this reconstruction method, the object model on the computer is modified using an optimization method so that the measured image of the object matches the image of the calculated object model. When the image of the object and the image of the object model finally match, the object model on the computer reproduces the actual object.

[0003] Non-Patent Document 1 proposes a method for reconstructing an object. In this method, an estimation device in which an LED array is arranged is used. The LED array is arranged at the pupil position of the illumination optical system. By changing the lighting position of the LED, illumination is irradiated at various angles onto the sample. Images of the sample are acquired at each irradiation angle, so that multiple images of the sample are acquired.

[0004] The reconstruction of the object yields the three-dimensional optical properties of the object, for example the refractive index distribution or the absorptance distribution.

[0005] In order to obtain the three-dimensional optical properties of an object with high accuracy and high spatial resolution, it is necessary to reconstruct the object with high accuracy and high spatial resolution.

[0006] With a highly accurate reconstruction of the object, the three-dimensional optical properties of the object can be obtained with high certainty both in directions perpendicular to the optical axis and parallel to the optical axis. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] “3D intensity and phase imaging from light field measurements in an LED array microscope”, Optica, 2, 104-111 (2015) Summary of the Invention [Problem to be solved by the invention]

[0008] When the thickness of an object is large, it is difficult for Non-Patent Document 1 to reconstruct the object with high accuracy and high spatial resolution.

[0009] The present invention has been made in consideration of such problems, and aims to provide an estimation device, an estimation system, an estimation method, and a recording medium that are capable of acquiring the three-dimensional optical characteristics of an object with high accuracy and high spatial resolution, even when the object is thick. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, an estimation device according to at least some embodiments of the present invention includes: A memory and a processor, The memory stores the first wavefront information and the second wavefront information; the first wavefront information is information about a wavefront acquired based on a first illumination light that has passed through an object; the second wavefront information is information about a wavefront acquired based on the second illumination light having passed through the object; the wavelength of the maximum intensity of the second illumination light is located on the shorter wavelength side than the wavelength of the maximum intensity of the first illumination light; The processor executes an estimation process to estimate three-dimensional optical properties of the object; The three-dimensional optical property is a refractive index distribution or an absorptivity distribution, The estimation process uses both the first wavefront information and the second wavefront information. 、 the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition; The processor executes the first optimization process multiple times; The processor executes the second optimization process multiple times. It is characterized by the above.

[0011] In accordance with at least some embodiments of the present invention, the estimation system comprises: The estimation device as described above; a light source unit that emits a first illumination light and a second illumination light; A photodetector; A stage on which an object is placed; An angle changing mechanism, The stage is disposed on the optical path between the light source unit and the photodetector, The angle changing mechanism is characterized by changing the angle of incidence of the first illumination light to the object and the angle of incidence of the second illumination light to the object. In accordance with at least some embodiments of the present invention, the estimation system comprises: The estimation device as described above; A stage on which an object is placed; a light detector and a light detector separate from the light detector, The stage is disposed on the optical path between the light source unit and the photodetector, The stage is characterized in that it is disposed on the optical path between the light source unit and the separate photodetector.

[0012] In accordance with at least some embodiments of the present invention, the estimation system comprises: The estimation device as described above; a light source unit that emits a first illumination light and a second illumination light, The light source unit is made up of multiple independent light sources with different irradiation angles. The estimation device is characterized in that a processor of the estimation device or a processor different from the processor controls whether or not to emit illumination light from the light source, thereby changing the angle of incidence of the first illumination light to the object and the angle of incidence of the second illumination light to the object. In accordance with at least some embodiments of the present invention, the estimation system comprises: mentioned above An estimation device for a light source unit that emits a first illumination light and a second illumination light; an imaging optical system for forming an optical image of an object; a photodetector for acquiring an image of the object from an optical image of the object; a drive mechanism for changing a distance between a focal position of the imaging optical system and a position of an object in an optical axis direction of the imaging optical system; The illumination by the first illumination light and the illumination by the second illumination light form partially coherent illumination on the object.

[0013] The estimation method according to at least some embodiments of the present invention comprises the steps of: 1. A method for estimating three-dimensional optical properties of an object, comprising: The three-dimensional optical property is a refractive index distribution or an absorptivity distribution, the first wavefront information is information about a wavefront acquired based on a first illumination light that has passed through an object; the second wavefront information is information about a wavefront acquired based on the second illumination light having passed through the object; the wavelength of the maximum intensity of the second illumination light is located on the shorter wavelength side than the wavelength of the maximum intensity of the first illumination light; Estimation process is performed using both the first and second wavefront information death, the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition; The first optimization process is performed multiple times. The second optimization process is performed multiple times.

[0014] A recording medium according to at least some embodiments of the present invention includes: A computer-readable recording medium having a program recorded thereon for causing a computer having a memory and a processor to execute an estimation process, the first wavefront information is information about a wavefront acquired based on a first illumination light that has passed through an object; the second wavefront information is information about a wavefront acquired based on the second illumination light having passed through the object; the wavelength of the maximum intensity of the second illumination light is located on the shorter wavelength side than the wavelength of the maximum intensity of the first illumination light; In the estimation process, the three-dimensional optical properties of the object are estimated, The three-dimensional optical property is a refractive index distribution or an absorptivity distribution, causing a processor to read the first wavefront information and the second wavefront information from a memory; Estimation process is performed using both the first and second wavefront information Let, the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition; causing the processor to execute the first optimization process multiple times; A computer-readable recording medium having a program recorded thereon for causing a processor to execute the second optimization process multiple times. Effect of the Invention

[0015] According to the present invention, it is possible to provide an estimation device, an estimation system, an estimation method, and a recording medium that are capable of acquiring three-dimensional optical characteristics of an object with high accuracy and high spatial resolution even when the object has a large thickness. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating an estimation device according to an embodiment of the present invention. [Diagram 2] 1 is a flowchart of a first acquisition method. [Diagram 3] FIG. 4 is a diagram showing a state in which a first illumination light passes through an object. [Figure 4] 13 is a diagram showing a state in which second illumination light passes through an object. FIG. [Diagram 5] 11 is a flowchart of a second acquisition method. [Figure 6] 11 is a flowchart of a first estimation process. [Figure 7] FIG. 13 is a diagram showing a measured image and an estimated image. [Figure 8] 13 is a flowchart illustrating a process for calculating estimated wavefront information. [Figure 9] 13 is a flowchart of a second estimation process. [Figure 10] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 11] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 12] FIG. 13 is a diagram showing a method for switching illumination light. [Figure 13] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 14] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 15] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 16] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 17] FIG. 2 shows an image of an object. [Figure 18] FIG. 2 shows an image of an object. [Figure 19] FIG. 1 is a diagram illustrating an estimation system according to an embodiment of the present invention. [Figure 20] FIG. 13 is a diagram showing an image of an aperture member and an object. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Prior to the description of the examples, the effects of an embodiment according to a certain aspect of the present invention will be described. In addition, when specifically explaining the effects of the present embodiment, specific examples will be shown. However, as in the case of the examples described later, the exemplified aspects are merely a part of the aspects included in the present invention, and there are many variations in the aspects. Therefore, the present invention is not limited to the exemplified aspects.

[0018] The estimation device of this embodiment includes a memory and a processor, and the memory stores first wavefront information and second wavefront information. The first wavefront information is information of a wavefront acquired based on a first illumination light that has passed through an object, and the second wavefront information is information of a wavefront acquired based on a second illumination light that has passed through the object. The wavelength of maximum intensity in the second illumination light is located on the shorter wavelength side than the wavelength of maximum intensity in the first illumination light. The processor executes an estimation process to estimate three-dimensional optical characteristics of the object, and the three-dimensional optical characteristics are a refractive index distribution or an absorptivity distribution. The estimation process uses both the first wavefront information and the second wavefront information.

[0019] FIG. 1 is a diagram showing an estimation device of this embodiment. The estimation device 1 includes a memory 2 and a processor 3. The memory 2 stores first wavefront information and second wavefront information. The processor 3 executes an estimation process for estimating three-dimensional optical characteristics of an object. The three-dimensional optical characteristics are a refractive index distribution or an absorptance distribution. The first wavefront information and the second wavefront information can be used in the estimation process.

[0020] The processor may be realized by an ASIC or FPGA, or may be a CPU. When the processor is realized by a CPU, the CPU reads the program from the memory and executes the process.

[0021] The first wavefront information is information on a wavefront obtained based on a first illumination light that has passed through an object. The second wavefront information is information on a wavefront obtained based on a second illumination light that has passed through an object.

[0022] The estimation process uses wavefront information. The more wavefront information there is, the better. With more wavefront information, the three-dimensional optical properties of the object can be estimated with higher accuracy.

[0023] The wavefront information is obtained based on illumination light that has passed through an object, and therefore the amount of wavefront information is affected by the wavelength of the illumination light.

[0024] The wavefront information includes any one of amplitude, phase, light intensity, and complex amplitude. The wavefront information is information on the wavefront at an imaging plane. The imaging plane is a plane where a photodetector detects light, and is also called an imaging plane.

[0025] Different wavelengths result in different spatial resolutions (hereafter referred to as "resolution"). In this case, there is a difference in the number of points required to extract wavefront information. Therefore, there may be a difference in the amount of wavefront information in both the direction perpendicular to the optical axis (hereafter referred to as the "lateral direction") and the direction parallel to the optical axis (hereafter referred to as the "axial direction").

[0026] The optical axis is for example the optical axis of an apparatus for measuring wavefront information. In the case of an apparatus equipped with detection optics, the optical axis is the optical axis of the detection optics.

[0027] Furthermore, when the wavelength is different, the degree of scattering of the illumination light is different. In this case, the arrival position of the illumination light inside the object differs in the axial direction. Therefore, the amount of wavefront information differs in the axial direction.

[0028] Furthermore, when the thickness of an object is large, the change that occurs when the illumination light passes through the object becomes large, and the phase information is folded into the range of -π to π, resulting in an uncertainty value that is an integer multiple of 2π, which may limit the amount of wavefront information. Since the phase change due to passing through an object depends on the wavelength, the limit on the amount of this wavefront information also depends on the wavelength.

[0029] Illumination light with a long wavelength has a lower resolution than illumination light with a short wavelength. Therefore, the amount of wavefront information that can be obtained is smaller in the lateral and axial directions than illumination light with a short wavelength. However, in the axial direction, illumination light can reach deeper inside the object than illumination light with a short wavelength.

[0030] In addition, when the thickness of an object is large, the ambiguity of the integral multiple of 2π in the phase information is less likely to occur with long-wavelength illumination light than with short-wavelength illumination light, and the amount of wavefront information is less limited. Therefore, the amount of wavefront information that can be obtained in the axial direction is greater than that with short-wavelength illumination light.

[0031] In the axial direction, the amount of wavefront information is small in terms of resolution, but large in terms of the arrival position of the illumination light. Overall, the amount of wavefront information in the axial direction is large for illumination light with a long wavelength compared to illumination light with a short wavelength.

[0032] Illumination light with a short wavelength has a higher resolution than illumination light with a long wavelength. Therefore, a larger amount of wavefront information can be obtained in the lateral and axial directions compared to illumination light with a long wavelength. However, in the axial direction, illumination light does not reach as deep inside an object as illumination light with a long wavelength. Therefore, a smaller amount of wavefront information can be obtained in the axial direction compared to illumination light with a long wavelength.

[0033] In the axial direction, the amount of wavefront information is large in terms of resolution, but is small in terms of the arrival position of the illumination light. Overall, the amount of wavefront information in the axial direction is smaller for short-wavelength illumination light than for long-wavelength illumination light.

[0034] The shorter the wavelength of the illumination light used to obtain the wavefront information, the less information there is in the axial direction, which leads to less accurate estimation in the axial direction.

[0035] To prevent the accuracy of the estimation in the axial direction from decreasing, wavefront information acquired with illumination light having a long wavelength can be used. However, as the wavelength of the illumination light increases, the diffraction angle increases, which reduces the resolution.

[0036] To prevent the resolution from decreasing, the numerical aperture of the optical system can be increased. However, increasing the numerical aperture narrows the field of view and reduces the working distance. Therefore, if the object is thick, it becomes difficult to obtain the wavefront information required for estimating the horizontal direction.

[0037] Therefore, when an object has a large thickness, it becomes difficult to obtain the three-dimensional optical properties of the object with high accuracy and high spatial resolution if the three-dimensional optical properties are estimated using only wavefront information acquired based on a single wavelength.

[0038] The estimation device 1 estimates the three-dimensional optical characteristics of the object using wavefront information acquired based on two wavelengths. The wavelength band of the first illumination light is different from the wavelength band of the second illumination light. Furthermore, the wavelength of maximum intensity in the second illumination light is located on the shorter wavelength side than the wavelength of maximum intensity in the first illumination light. Therefore, the amount of wavefront information can be increased. As a result, the three-dimensional optical characteristics of the object can be acquired with high accuracy and high spatial resolution.

[0039] The maximum intensity is the maximum value of the peaks (maximum values). There may be multiple peaks. Specifically, for example, a laser or a quasi-monochromatic LED may be used as the light source of the first illumination light and the light source of the second illumination light. For the first illumination light and the second illumination light, light of a single wavelength or light of a wavelength that can be regarded as a monochromatic wavelength in terms of optical calculation may be used. For the first illumination light and the second illumination light, light with a narrow wavelength band may be used. The half-width of the first illumination light and the second illumination light is preferably 50 nm or less.

[0040] The wavefront information can be obtained, for example, from interference fringes. The interference fringes are formed by measurement light and reference light. The measurement light is illumination light that has passed through an object. The reference light is illumination light that does not pass through an object. Parallel light is used as the illumination light.

[0041] When estimating the wavefront based on the light intensity, an image can be used as the wavefront information. When an image is used as the wavefront information, it is not necessary to analyze the image to obtain the wavefront information.

[0042] Wavefront information can be obtained by analyzing an image of interference fringes. Therefore, it is necessary to obtain the image of interference fringes. A method for obtaining an image of interference fringes will be described below.

[0043] 2 is a flowchart of the first acquisition method. In the first acquisition method, the wavelength of the illumination light is changed.

[0044] In step S10, the number of times Nλ to change the wavelength is set. For example, if the wavelength of the illumination light is changed three times, the value of the number of times Nλ to change the wavelength is set to 3. Although the number of times Nλ to change the wavelength is described as 3, any value equal to or greater than 2 may be used.

[0045] In step S20, the wavelength λ(n) is set. In setting the wavelength λ(n), for example, the value of the wavelength λ(n) is set so that the wavelength becomes shorter as the value of the variable n increases. In this case, the longest wavelength is set to the value of λ(1).

[0046] For example, set the value of λ(1) to 1500 nm, the value of λ(2) to 650 nm, and the value of λ(3) to 480 nm. 1500 nm, 650 nm, and 480 nm are the wavelengths at maximum intensity. The wavelengths are explained with units attached to the numerical values. In practice, only the numerical values ​​are set.

[0047] The wavelength λ(n) may be set so that the wavelength becomes longer as the variable n increases. Also, (n) may be set so that the magnitude of the variable n and the length of the wavelength are random. Random settings can be realized by defining them in advance in a table.

[0048] In step S30, the value of the variable n is set to 1.

[0049] In step S40, illumination light is selected based on the value of wavelength λ(n). When the light source emits light of one wavelength, a light source that emits light of a wavelength that matches the value of wavelength λ(n) is selected. A laser can be used as the light source.

[0050] When the light source emits multiple wavelengths, it is possible to select one wavelength of light using an optical filter. In this case, an optical filter that transmits light with a wavelength that matches the value of the wavelength λ(n) is selected.

[0051] In step S50, an image of the interference fringes I(n) is acquired. The interference fringes I(n) are formed by irradiating the object with illumination light. The interference fringes I(n) are imaged by a photodetector, so that the image of the interference fringes I(n) can be acquired.

[0052] The value of the variable n represents an ordinal number related to wavelength, so the interference fringe I(n) represents the interference fringe formed at the nth wavelength.

[0053] As described above, the wavelength is set so that the wavelength becomes shorter as the value of the variable n increases. Therefore, in the interference fringes I(n), the wavelength of the illumination light used to form the interference fringes becomes shorter as the value of the variable n increases.

[0054] In step S60, it is determined whether the value of the variable n coincides with the value of the number of changes Nλ. If the result of the determination is NO, step S70 is executed. If the result of the determination is YES, the process ends.

[0055] (If the result is NO: n ≠ Nλ) Step S70 is executed. In step S70, 1 is added to the value of variable n. When step S70 is completed, the process returns to step S40. In step S70, the value of variable n is incremented by 1. Therefore, step S50 is executed using a different illumination light. Step S50 is repeated until all illumination lights have been used. (If the result is YES: n=Nλ) The acquisition of interference fringe images is terminated. The acquisition of interference fringe images is performed Nλ times. Therefore, Nλ images of interference fringes are acquired. In the above example, the value of the number of wavelength changes Nλ is set to 3. Therefore, three images of interference fringes are acquired.

[0056] Wavefront information can be obtained from the interference fringes. The wavefront information obtained from the interference fringes I(n) is called wavefront information W(n).

[0057] The wavelength of the second illumination light is shorter than the wavelength of the first illumination light, and the longest wavelength in the wavelength band of the second illumination light is located on the shorter wavelength side than the shortest wavelength in the wavelength band of the first illumination light.

[0058] In the above example, the value of λ(1) is set to 1500 nm, the value of λ(2) is set to 650 nm, and the value of λ(3) is set to 480 nm. Therefore, the first illumination light corresponds to illumination light with a value of λ(1). The second illumination light corresponds to illumination light with a value of λ(2) or illumination light with a value of λ(3). Alternatively, the first illumination light corresponds to λ(2), and the second illumination light corresponds to λ(3).

[0059] The Nλ images of the interference fringes include a first image and a second image. The first image is an image of the interference fringes formed by the first illumination light. The second image is an image of the interference fringes formed by the second illumination light.

[0060] The wavefront information W(n) includes the first wavefront information and the second wavefront information. Therefore, the wavefront information W(n) is stored in the memory 2. At this time, the value of the wavelength λ(n) is also stored in the memory 2.

[0061] As described above, the processor 3 executes an estimation process for estimating the three-dimensional optical characteristics of the object. In the estimation process, the processor 3 executes an estimation of the three-dimensional optical characteristics of the object using both the first wavefront information and the second wavefront information.

[0062] In the estimation device of this embodiment, the memory stores a plurality of first wavefront information and a plurality of second wavefront information, the angle of incidence of the first illumination light with respect to the object differs for each of the plurality of first wavefront information, and the angle of incidence of the second illumination light with respect to the object differs for each of the plurality of second wavefront information, and it is preferable that the estimation process uses both the plurality of first wavefront information and the plurality of second wavefront information.

[0063] The estimation process uses a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information, and therefore the memory stores a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information.

[0064] The first wavefront information is wavefront information acquired based on the first illumination light that has passed through the object. In each of the multiple pieces of first wavefront information, the angle of incidence of the first illumination light with respect to the object is different.

[0065] Fig. 3 is a diagram showing how the first illumination light passes through an object. Fig. 3(a), Fig. 3(b), and Fig. 3(c) are diagrams showing how the direction of the first illumination light changes. Fig. 3(d), Fig. 3(e), and Fig. 3(f) are diagrams showing how the direction of the object changes.

[0066] 3(a), 3(b), and 3(c), the direction of the first illumination light Lλ1 is changed without changing the direction of the object 10. Therefore, the angle of incidence of the first illumination light Lλ1 with respect to the object 10 changes. θL is the angle between the first illumination light Lλ1 and the optical axis AX. In FIG. 3(a), θL=-20°, in FIG. 3(b), θL=0°, and in FIG. 3(c), θL=+20°.

[0067] In Fig. 3(d), Fig. 3(e), and Fig. 3(f), the direction of the object 10 is changed without changing the direction of the first illumination light Lλ1. Therefore, the direction of the object 10 with respect to the first illumination light Lλ1 changes. θS is the inclination angle of the object. In Fig. 3(d), θS = -20°, in Fig. 3(e), θS = 0°, and in Fig. 3(f), θS = +20°.

[0068] 3(d), 3(e), and 3(f), the direction of the first illumination light Lλ1 does not change. Therefore, the incident angle of the first illumination light Lλ1 with respect to the object 10 does not appear to change. However, since the direction of the object 10 changes, the incident angle of the first illumination light Lλ1 with respect to the object 10 actually changes.

[0069] The second wavefront information is wavefront information acquired based on the second illumination light having passed through the object. In each of the multiple pieces of second wavefront information, the angle of incidence of the second illumination light with respect to the object is different.

[0070] Fig. 4 is a diagram showing how the second illumination light passes through an object. Fig. 4(a), Fig. 4(b), and Fig. 4(c) are diagrams showing how the direction of the second illumination light changes. Fig. 4(d), Fig. 4(e), and Fig. 4(f) are diagrams showing how the direction of the object changes.

[0071] 4(a), 4(b), and 4(c), the direction of the second illumination light Lλ2 is changed without changing the direction of the object 10. Therefore, the angle of incidence of the second illumination light Lλ2 with respect to the object 10 changes. θL is the angle between the second illumination light Lλ2 and the optical axis AX. In FIG. 4(a), θL=-20°, in FIG. 4(b), θL=0°, and in FIG. 4(c), θL=+20°.

[0072] In Fig. 4(d), Fig. 4(e), and Fig. 4(f), the direction of the object 10 is changed without changing the direction of the second illumination light Lλ2. Therefore, the direction of the object 10 with respect to the second illumination light Lλ2 changes. θS is the inclination angle of the object. In Fig. 4(d), θS = -20°, in Fig. 4(e), θS = 0°, and in Fig. 4(f), θS = +20°.

[0073] 4(d), 4(e), and 4(f), the direction of the second illumination light Lλ2 does not change. Therefore, the incident angle of the second illumination light Lλ2 with respect to the object 10 does not appear to change. However, since the direction of the object 10 changes, the incident angle of the second illumination light Lλ2 with respect to the object 10 actually changes.

[0074] The incident angle of the illumination light with respect to the object can be replaced with the relative direction between the illumination light and the object (hereinafter referred to as the "relative direction").

[0075] As described above, the wavefront information is obtained based on the illumination light that has passed through the object, and therefore the amount of wavefront information is affected by the relative direction.

[0076] By changing the relative angle, wavefront information can be acquired for each change. This allows the amount of wavefront information to be increased. Furthermore, when the relative angle differs, the area through which the illumination light passes inside the object differs. Wavefront information in one relative direction contains information that is not included in wavefront information in other relative directions. This allows the amount of wavefront information to be increased.

[0077] In the plurality of pieces of first wavefront information, the angle of incidence of the first illumination light with respect to the object differs for each piece of second wavefront information. In the plurality of pieces of second wavefront information, the angle of incidence of the second illumination light with respect to the object differs for each piece of second wavefront information. This makes it possible to increase the amount of wavefront information. As a result, it is possible to acquire the three-dimensional optical characteristics of the object with high accuracy and high spatial resolution.

[0078] Fig. 5 is a flow chart of the second acquisition method. The same steps as in Fig. 2 are given the same numbers and their explanations are omitted. In the second acquisition method, the wavelength and relative direction of the illumination light are changed.

[0079] In step S21, the number of times Nθ to change the angle is set. The angle to be changed is the relative direction. For example, if the relative direction is to be changed five times, the number of times Nθ to change the angle is set to 5.

[0080] The deviation in the relative direction can be expressed as an angle. In what follows, the deviation in the relative direction will be expressed as the relative angle θ(m). When the relative orientations of the illumination light and the object are consistent, the deviation in the relative direction is 0°. In this case, the value of the relative angle θ(m) is set to 0°.

[0081] In step S22, the relative angle θ(m) is set. In setting the relative angle θ(m), for example, the value of θ(1) is set to 0°, the value of θ(2) is set to 4°, the value of θ(3) is set to 7°, the value of θ(4) is set to 10°, and the value of θ(5) is set to 15°.

[0082] Alternatively, an initial value and an increment may be set. In this case, an initial value is set for the value of θ(1), and the initial value plus the increment is set for the values ​​of θ(2), θ(3), θ(4), and θ(5).

[0083] The angles are explained with units attached to the numerical values. In practice, only the numerical values ​​are set.

[0084] In step S31, the value of the variable m and the value of the variable n are set to 1.

[0085] In step S32, positioning is performed based on the relative angle θ(m). The object to be positioned is the illumination light or the object. In positioning, the direction of the illumination light is changed so that the angle between the illumination light and the optical axis coincides with the value of the relative angle θ(m). Alternatively, the object is rotated so that the orientation of the object relative to the illumination light coincides with the value of the relative angle θ(m).

[0086] In step S51, an image of the interference fringes I(m,n) is acquired. The interference fringes I(m,n) are formed by irradiating an object with illumination light. The interference fringes I(m,n) are imaged by a photodetector, whereby the image of the interference fringes I(m,n) can be acquired.

[0087] The value of the variable m represents an ordinal number related to the relative angle. The value of the variable n represents an ordinal number related to the wavelength. Therefore, the interference fringe I(m,n) represents the interference fringe formed at the mth relative angle and the nth wavelength.

[0088] As described above, the wavelength λ(n) can be set so that, for example, the wavelength becomes shorter as the value of the variable n increases. In this case, in the interference fringes I(m,n), the wavelength of the illumination light used to form the interference fringes becomes shorter as the value of the variable n increases.

[0089] In the case where the wavelength is set to be longer as the variable n increases, in the interference fringes I(m,n), the wavelength of the illumination light used to form the interference fringes becomes longer as the value of the variable n increases.

[0090] In step S60, it is determined whether the value of the variable n coincides with the value of the number of changes Nλ. If the result of the determination is NO, step S40 is executed. If the result of the determination is YES, step S80 is executed.

[0091] (If the result is YES: n=Nλ) Step S80 is executed. In step S80, it is determined whether the value of the variable m coincides with the value of the number of times Nθ of angle changes. If the result of the determination is NO, step S90 is executed. If the result of the determination is YES, the process ends.

[0092] (If the result is NO: m ≠ Nθ) Step S90 is executed. In step S90, 1 is added to the value of variable m. When step S90 is completed, the process returns to step S32. In step S90, the value of variable m is incremented by 1. Therefore, steps S40 and S51 are executed at a different relative angle. Steps S40 and S51 are repeated until positioning is completed at all relative angles.

[0093] (If the result is YES: m=Nθ) The acquisition of interference fringe images is terminated. The acquisition of interference fringe images is performed (Nλ×Nθ) times. Therefore, (Nλ×Nθ) images of interference fringes are acquired. In the above example, the value of the number of angle changes Nθ is set to 5, and the value of the number of wavelength changes Nλ is set to 3. Therefore, 15 images of interference fringes are acquired.

[0094] Wavefront information can be obtained from the interference fringes. The wavefront information obtained from the interference fringes I(m,n) is defined as wavefront information W(m,n).

[0095] The wavelength of the second illumination light is shorter than the wavelength of the first illumination light. In the above example, the value of λ(1) is set to 1500 nm, the value of λ(2) is set to 650 nm, and the value of λ(3) is set to 480 nm. Therefore, the first illumination light corresponds to illumination light with a value of λ(1). The second illumination light corresponds to illumination light with a value of λ(2) or illumination light with a value of λ(3). Furthermore, when the first illumination light corresponds to illumination light with a value of λ(2), the second illumination light corresponds to illumination light with a value of λ(3).

[0096] The (Nλ×Nθ) images of the interference fringes include a plurality of first images and a plurality of second images. The first images are images of the interference fringes formed by the first illumination light. The second images are images of the interference fringes formed by the second illumination light.

[0097] The first images include images of interference fringes where the first illumination light is incident on the object at different angles. Thus, it is possible to obtain a plurality of pieces of first wavefront information from the first images. The second images include images of interference fringes where the second illumination light is incident on the object at different angles. Thus, it is possible to obtain a plurality of pieces of second wavefront information from the second images.

[0098] The wavefront information W(m,n) includes a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information. Therefore, the wavefront information W(m,n) is stored in the memory 2. At this time, the value of the number of times the angle is changed Nθ, the value of the relative angle θ(m), and the value of the wavelength λ(n) are also stored in the memory 2.

[0099] As described above, the processor 3 executes an estimation process for estimating the three-dimensional optical characteristics of the object. In the estimation process, the processor 3 executes an estimation of the three-dimensional optical characteristics of the object using both the plurality of pieces of first wavefront information and the plurality of pieces of second wavefront information.

[0100] In the second acquisition method, the interference fringes formed by the first illumination light and the interference fringes formed by the second illumination light are acquired at one relative angle. However, after the interference fringes formed by the first illumination light are acquired at all relative angles, the interference fringes formed by the second illumination light may be acquired at all relative angles.

[0101] In the estimation device of this embodiment, it is preferable that the estimation process includes a first optimization process using the first wavefront information as a constraint condition and a second optimization process using the second wavefront information as a constraint condition, and that the processor continuously executes the second optimization process on the three-dimensional optical characteristics updated by continuously executing the first optimization process.

[0102] Wavefront information is used to estimate the three-dimensional optical properties of an object. To obtain the wavefront information, it is necessary to obtain the wavefront that has passed through the object. In the estimation device of this embodiment, the wavefront is obtained using the beam propagation method. Instead of the beam propagation method, FDTD (Finite Difference Time Domain) may be used.

[0103] The second wavefront information is information when the second illumination light is used. The wavelength band of the second illumination light is located on the shorter wavelength side than the wavelength band of the first illumination light. Therefore, when the second wavefront information is used, the three-dimensional optical characteristics can be estimated with high accuracy in the lateral direction, but the three-dimensional optical characteristics cannot be roughly estimated in the axial direction.

[0104] In contrast, the first wavefront information is information obtained when the first illumination light is used. The wavelength band of the first illumination light is located on the longer wavelength side than the wavelength band of the second illumination light. Therefore, by using the first wavefront information, it is possible to roughly estimate the three-dimensional optical characteristics not only in the lateral direction but also in the axial direction.

[0105] Therefore, the first wavefront information is first used to roughly estimate the 3D optical properties in all directions. After the rough estimation is completed, the second wavefront information is used to accurately estimate the 3D optical properties. By performing the estimation in this order, the 3D optical properties of an object can be obtained efficiently, with high accuracy and high spatial resolution.

[0106] 6 is a flowchart of the first estimation process. The first estimation process includes steps S100, S200, S300, S400, and S500.

[0107] In step S100, various settings are made.

[0108] Step S100 includes steps S110, S120, S130, and S140. Step S150 may be provided as necessary.

[0109] In step S110, the number of times the angle is changed Nθ is set. The value of the number of times the angle is changed Nθ is stored in the memory 2. Therefore, the value stored in the memory 2 may be set as the value of the number of times the angle is changed Nθ. For example, if 5 is stored in the memory 2, the value of the number of times the angle is changed Nθ is set to 5.

[0110] In step S120, the wavelength λ(n) is set. The value of the wavelength λ(n) is stored in the memory 2. By setting the wavelength to be used in advance, the process can be carried out without displaying it.

[0111] All values ​​of wavelength λ(n) may be read out from memory 2 and displayed. For example, if 1500 nm, 650 nm, and 480 nm are stored in memory 2, these values ​​may be displayed. The displayed values ​​represent wavelengths. Therefore, it is possible to select multiple wavelengths to be used for estimation from among the displayed wavelengths.

[0112] In setting the wavelength λ(n), for example, a selected value is set for the wavelength λ(n) so that the wavelength becomes shorter as the value of n increases, in which case the value of λ(1) is set to the value of the wavelength with maximum intensity.

[0113] For example, when 1500 nm, 650 nm, and 480 nm are selected, the value of the wavelength λ(n) is set as follows: Value of λ(1): 1500 nm Value of λ(2): 650 nm Value of λ(3): 480 nm

[0114] In step S130, a variable Nλ', the number of wavelengths, is set. The number of wavelengths is the number of selected wavelengths. The number of selected wavelengths is obtained by selecting the wavelengths to be used for estimation. The value of the number of wavelengths Nλ' is set to the number of selected wavelengths. In the above example, the number of selected wavelengths is 3, so the value of the number of wavelengths Nλ' is set to 3. The number of wavelengths to be selected may be any number equal to or greater than 2.

[0115] In step S140, the number of iterations N(n) is set. The number of iterations N(n) is the number of times the optimization process is executed. The optimization process includes a first optimization process and a second optimization process. The first optimization process and the second optimization process will be described later.

[0116] The variable n is used for the number of repetitions N(n) and the wavelength λ(n). Therefore, when setting the number of repetitions N(n), the number of repetitions is set for the value (wavelength) set for the wavelength λ(n).

[0117] In the above example, the number of selected wavelengths is 3. The value of the number of iterations N(n) is set, for example, as follows: Value of N(1): 3 times Value of N(2): 2 times Value of N(3): 2 times

[0118] When step S150 is provided, in step S150, an initial value is set to the estimated value. The estimated value is a value of the three-dimensional optical characteristic of the estimated object. The three-dimensional optical characteristic is estimated by simulation. The simulation is performed using the estimated object. By setting the initial value to the estimated value, the simulation can be performed.

[0119] In step S200, various initializations are performed.

[0120] Step S200 includes step S210, step S220, and step S230.

[0121] In step S210, the value of variable n is set to 1. In step S220, the value of variable m is set to 1. In step S230, the value of variable m is set to 1.

[0122] In step S300, an estimation process is performed to estimate three-dimensional optical characteristics of an object.

[0123] Step S300 includes step S400, step S410, step S420, step S430, step S440, and step S450.

[0124] In the estimation process, for example, an evaluation value is used. The evaluation value is expressed as a difference between the wavefront information of the measurement light and the wavefront information by the simulation, or a ratio between the wavefront information of the measurement light and the wavefront information by the simulation. The wavefront information is information including, for example, any one of amplitude, phase, light intensity, and complex amplitude.

[0125] Wavefront information by simulation (hereinafter referred to as "estimated wavefront information") is calculated from an estimated image. The estimated image is an image obtained by light transmitted through an estimated object. The light transmitted through the estimated object is light by simulation. Wavefront information of the measurement light (hereinafter referred to as "measured wavefront information") is calculated from the measurement image.

[0126] The measured image is an image of the object captured by an optical device, and the estimated image is an image of the estimated object captured by a simulation.

[0127] Fig. 7 is a diagram showing a measured image and an estimated image. Fig. 7(a) is a diagram showing how the measured image is acquired. Fig. 7(b) and Fig. 7(c) are diagrams showing how the estimated image is acquired.

[0128] 7(a), an object 20 and a measurement optical system 21 are used to acquire a measurement image. The measurement optical system 21 has a lens 22.

[0129] In FIG. 7(a), position Z fo indicates the position of the focal point of the measurement optical system 21. Position Z s indicates the position of the image side of the object 20.

[0130] In the measurement optical system 21, position Z fo In FIG. 7(a), an optical image of an object 20 at a position Z s The inside of the object 20, which is ΔZ away from the fo It matches.

[0131] A CCD 23 is disposed on the imaging plane IM. An optical image of the object 20 is captured by the CCD 23. As a result, an image of the optical image of the object 20 (hereinafter, “measurement image I”) is mea ") can be obtained. Measurement image I mea From this, the measured wavefront information is calculated.

[0132] Since the optical image is an image of light intensity, the measurement image I mea is also an image of light intensity. mea is an image of light intensity, so the measured image I mea The measured wavefront information calculated from is light intensity. When light intensity is used, the measured image can also be used as wavefront information.

[0133] The estimated wavefront information is an image of an optical image of the estimated object 24 (hereinafter, “estimated image I est " is calculated from the

[0134] FIG. 7(c) illustrates the measurement optical system 21. Estimated image I est Since the calculation of is performed by simulation, the measurement optical system 21 does not physically exist. Therefore, the estimated image I est In the calculation of the above, the pupil function of the measurement optical system 21 is used.

[0135] Estimated image I est is obtained from the image of the estimated object 24 on the image plane IM. mea is an image of light intensity, so the estimated image I est Therefore, it is necessary to calculate the light intensity of the estimated object 24 on the imaging plane IM.

[0136] In step S400, estimated wavefront information is calculated.

[0137] 8 is a flowchart showing the calculation of estimated wavefront information. Step S400 includes steps S401, S402, S403, S404, and S405.

[0138] The calculation of the estimated wavefront information is based on the forward propagation of the wavefront. This is the propagation of the wavefront in the direction in which the illumination light travels. Reverse propagation is the propagation of the wavefront in the opposite direction to the direction in which the illumination light travels. In forward propagation, the wavefront propagates from the estimated object 24 towards the imaging plane IM, as shown in Figures 7(b) and 7(c).

[0139] In step S401, a wavefront incident on an estimated object is calculated.

[0140] position Z in is the position of the surface of the estimated object 24 that corresponds to the surface of the object 20 on the light source (illumination) side. in is the position of the surface on the side where the simulated light is incident on the estimated object 24. Therefore, the position Z in Wavefront U in Calculate the wavefront U inFor the measurement light, the same wavefront as that of the measurement light irradiated on the object 20 can be used.

[0141] In step S402, a wavefront emerging from the estimated object is calculated.

[0142] position Z out is the position of the surface of the estimated object 24 corresponding to the surface of the object 20 on the image formation side (lens side, CCD side). out is the position of the surface from which the simulated light emerges from the estimated object 24. out Wavefront U out Calculate the wavefront U out For example, using the beam propagation method, we can calculate the wavefront U in It can be calculated from:

[0143] In step S403, the wavefront at a predetermined acquisition position is calculated.

[0144] The predetermined acquisition position is the position on the object side when the measurement image is acquired. The predetermined acquisition position is the position Z in From position Z out Position Z is any position between p is one of the predetermined acquisition positions. Position Z p is a position conjugate to the image plane IM.

[0145] Estimated image I est is the measurement image I mea It is calculated under the same conditions as measurement image I. mea is the position Z s The estimated image I is obtained from an optical image of the inside of the object 20 located ΔZ away from the est In the calculation, position Z s We need the wavefront at a position ΔZ away from

[0146] In Fig. 7(b), position Z out is position Z s It corresponds to position Z. out The position ΔZ away from is position Z p Therefore, position Z pWavefront U p It is sufficient if we can calculate

[0147] position Z p is the position Z out Therefore, the wavefront U out The wavefront U p It cannot be used as a wavefront U p For example, using the beam propagation method, we can calculate the wavefront U out It can be calculated from:

[0148] In step S404, the wavefront on the imaging plane is calculated.

[0149] Wavefront U p The wavefront U passes through the measurement optical system 21 and reaches the image plane IM. img is the wavefront U p can be calculated from the pupil function of the measurement optical system 21.

[0150] In step S405, estimated wavefront information on the imaging plane is calculated.

[0151] Wavefront U img represents the amplitude of light. Light intensity is expressed as the square of the amplitude. Therefore, the wavefront U img By squaring the light intensity of the estimated object 24, the light intensity of the estimated image I est The estimated image I est From this, estimated wavefront information is calculated.

[0152] Instead of the light intensity, the amplitude and phase may be used. The amplitude and phase are expressed using the electric field. Therefore, when the amplitude and phase are used, values ​​calculated from the electric field are used for the measured value and the estimated value. The electric field Emes based on the measurement and the electric field Eest based on the estimation are expressed by the following formulas.

[0153] Emes = Ames × exp(i × Pmes) Eest = Aest × exp(i × Pest) Where: Pmes is the phase based on the measurement, Ames is the amplitude based on measurements, Pest is the estimated phase, Aest is the estimated amplitude, It is.

[0154] In obtaining the electric field E mes based on the measurement, the measurement light and the reference light are incident on the photodetector in a non-parallel state.

[0155] In the photodetector, the measurement light and the reference light form an interference fringe on the imaging plane of the photodetector. The interference fringe is imaged by the photodetector. As a result, an image of the interference fringe can be obtained.

[0156] The interference fringes are acquired with the measurement and reference beams in a non-parallel state. Thus, by analyzing the interference fringes, the measured phase and measured amplitude can be obtained. As a result, the measured electric field Emes is obtained. The estimated electric field Eest can be obtained by simulation.

[0157] Moreover, the complex amplitude can be obtained by analyzing the interference fringes, so the complex amplitude may be used as wavefront information instead of the light intensity.

[0158] Continuing the explanation by returning to Fig. 6, in step S410, the estimated wavefront information is constrained by the wavefront information W(m,n).

[0159] The wavefront information W(m,n) is obtained from an image of the interference fringes I(m,n). The interference fringes I(m,n) are formed by the measurement light. Therefore, the wavefront information W(m,n) can be regarded as the measured wavefront information described in step S400.

[0160] The value of the variable m represents an ordinal number related to the relative angle. The value of the variable n represents an ordinal number related to the wavelength. The wavefront information W(m,n) represents the measured wavefront information when the mth relative angle and the nth wavelength are used.

[0161] In step S210, the value of variable n is set to 1. As described in step S120, in setting the wavelength λ(n), the value of wavelength λ(n) is set so that the wavelength becomes shorter as the value of variable n increases. Therefore, when the value of variable n is 1, the value of λ(n) is set to the longest wavelength.

[0162] When the value of the variable n is 1, the wavefront information W(m,n) is the wavefront information when the longest wavelength is used. The longest wavelength is the wavelength of the first illumination light. Therefore, when the value of the variable n is 1, the wavefront information W(m,n) is the wavefront information when the first illumination light is used.

[0163] The wavefront information when the first illumination light is used is the first wavefront information. Therefore, when the value of the variable n is 1, the wavefront information W(m,n) becomes the first wavefront information. In this case, the process in step S410 becomes a process of constraining the estimated wavefront information with the first wavefront information.

[0164] The first optimization process is a process that uses the first wavefront information as a constraint. When the value of the variable n is 1, the estimated wavefront information is constrained by the first wavefront information in step S410. Therefore, in this case, the process in step S410 is the first optimization process.

[0165] As described later, the value of the variable n changes. Therefore, the value of the variable n can be set to a value other than 1. In this case, the value of the wavelength λ(n) becomes the value of a different wavelength.

[0166] The another wavelength is a wavelength shorter than the longest wavelength. The longest wavelength is the wavelength of the first illumination light. The wavelength of the second illumination light is shorter than the wavelength of the first illumination light. Thus, the another wavelength is the wavelength of the second illumination light.

[0167] When the value of the variable n is other than 1, the wavefront information W(m,n) is wavefront information when a different wavelength is used. The different wavelength is the wavelength of the second illumination light. Therefore, when the value of the variable n is other than 1, the wavefront information W(m,n) is wavefront information when the second illumination light is used.

[0168] The wavefront information when the second illumination light is used is the second wavefront information. Therefore, when the value of the variable n is 2, the wavefront information W(m,n) becomes the second wavefront information. In this case, the process in step S410 is a process of constraining the estimated wavefront information with the second wavefront information. When the value of the variable n is 3, the wavefront information W(m,n) becomes the third wavefront information. In this case, the process in step S410 is a process of constraining the estimated wavefront information with the third wavefront information.

[0169] The second optimization process is a process that uses the second wavefront information as a constraint. When the value of the variable n is 2, the estimated wavefront information is constrained by the second wavefront information in step S410. Therefore, in this case, the process in step S410 becomes the second optimization process. When the value of the variable n is 3, the estimated wavefront information is constrained by the third wavefront information in step S410. Therefore, in this case, the process in step S410 becomes the third optimization process.

[0170] Measurement image I mea The measured wavefront information is calculated from the estimated image I est The estimated wavefront information is calculated from the difference between the measured wavefront information and the estimated wavefront information, or the ratio between the measured wavefront information and the estimated wavefront information. Constraining the estimated wavefront information by the measured wavefront information means correcting the estimated wavefront information using the measured wavefront information, or calculating the error between the estimated wavefront information and the measured wavefront information, and is almost synonymous with calculating an evaluation value.

[0171] Measurement image I mea and estimated image I est Difference between or measured image I mea and estimated image I est The ratio of the above may be used as the evaluation value.

[0172] In step S420, the evaluation value is compared with a threshold value.

[0173] When the evaluation value is expressed by the difference between the measured wavefront information and the estimated wavefront information, the difference between the measured wavefront information and the estimated wavefront information is calculated as the evaluation value. The evaluation value is compared with a threshold. If the determination result is NO, step S500 is executed. If the determination result is YES, step S430 is executed.

[0174] (If the result is NO: threshold value ≧ evaluation value) Execute step S500.

[0175] In step S500, the three-dimensional optical characteristics of the estimated object are calculated.

[0176] The obtained three-dimensional optical properties of the estimated object 24 are identical or substantially identical to the three-dimensional optical properties of the object 20. By using the three-dimensional optical properties obtained in step S500, a reconstructed estimated object can be obtained.

[0177] The reconstructed estimated object may be output, for example, to a display device.

[0178] As described above, the three-dimensional optical properties obtained in step S500 are identical or nearly identical to the three-dimensional optical properties of the object 20. Therefore, the reconstructed estimated object can be considered to be identical or nearly identical to the structure of the object 20.

[0179] (If the result is YES: threshold value <= evaluation value) Execute step S430. In step S430, the gradient is calculated.

[0180] Step S430 includes step S431 and step S432.

[0181] The calculation of the gradient is based on the backpropagation of the wavefront. In backpropagation, the wavefront moves to position Z out From position Z in It propagates towards.

[0182] In step S431, the corrected wavefront is calculated.

[0183] When calculating using light intensity, an image can be used as wavefront information. p In the calculation of mea and estimated image I est is used. Wavefront U' p is the position Z p The wavefront at

[0184] As shown in Fig. 7(c), the estimated image I est is the wavefront U img The wavefront U img is the wavefront U p It is calculated based on:

[0185] When step S150 is provided, the wavefront U p The calculation uses the initial value set in step S150. The initial value is the value of the three-dimensional optical property of the estimated object 24. When step S430 is executed for the first time, the initial value is different from the value of the three-dimensional optical property of the object 20 (hereinafter referred to as the "object property value").

[0186] The larger the difference between the initial value and the object characteristic value, the smaller the estimated image I est and measurement image I mea Therefore, the difference between the estimated image I est and measurement image I mea The difference between can be considered to reflect the difference between the initial value and the object property value.

[0187] When calculating the light intensity, an image can be used as wavefront information. est (r) and measurement image I mea (r) and the wavefront U p As a result, the wavefront after correction, that is, the wavefront U' p is obtained.

[0188] Wavefront U' p is expressed, for example, by the following formula (1). U' p =U p ×√(Imea / I est ) (1)

[0189] In step S432, the gradient is calculated.

[0190] The calculation of the gradient can be based on the back-propagation of the wavefront.

[0191] In the reverse propagation of the wavefront, position Z out From position Z in Therefore, in order to calculate the gradient, the wavefront toward the position Z out The corrected wavefront (hereinafter referred to as "wavefront U' out " is necessary.

[0192] Wavefront U' p is the wavefront U p Since the wavefront is corrected, the wavefront U' p is position Z p In FIG. 7(c), for ease of viewing, the wavefront U' p is the position Z p In FIG. 7(b), the wavefront U' out is the position Z out 1 is shown in a displaced position.

[0193] As shown in Fig. 7(b) and Fig. 7(c), at position Z out is the position Z p Therefore, the wavefront U' is p Let U' be the wavefront out It cannot be used as the wavefront U'. out is expressed as the wavefront U' by using the beam propagation method, for example. p It can be calculated from:

[0194] Wavefront U' out Once calculated, the wavefront is calculated based on the backpropagation of the wavefront. In the backpropagation of the wavefront, the wavefront propagating inside the estimated object 24 is calculated. In the calculation of the wavefront, the wavefront U out and U' out and are used.

[0195] Wavefront U' p is the wavefront U p Therefore, the wavefront U' out Also, the wavefront U out Wave surface U' is different. out and the wavefront U out Using the gradient, the gradient can be calculated. The gradient is the gradient of the wavefront at any location in the object. The gradient contains new information about the values ​​of the three-dimensional optical properties of the estimated object 24.

[0196] In step S461, it is determined whether the value of the variable m coincides with the value of the number of times N.theta. of angle changes. If the result of the determination is NO, step S462 is executed. If the result of the determination is YES, step S440 is executed.

[0197] (If the result is NO: m ≠ Nθ) Step S462 is executed. In step S462, the value of the variable m is incremented by 1. When step S462 is completed, the process returns to step S400.

[0198] In step S462, the value of the variable m is incremented by 1. In this case, the value of m in the wavefront information W(m,n) changes. Therefore, steps S400 to S430 are executed using wavefront information at a different relative angle. Steps S400 to S430 are repeated until positioning is completed at all relative angles.

[0199] In the above example, the value of the number of angle changes Nθ is set to 5. Therefore, steps S400 to S430 are executed five times.

[0200] For example, when the relative angles are different between wavefront information A and wavefront information B, wavefront information A contains information not included in wavefront information B, and wavefront information B contains information not included in wavefront information A. Therefore, the more wavefront information with different relative angles there is, the greater the amount of information.

[0201] With a larger amount of information, the corrected wavefront can be calculated more accurately in step S431. As a result, the accuracy of the gradient is also improved. The gradient contains information about the difference between the estimated value and the object characteristic value. By increasing the accuracy of the gradient, the difference between the estimated value and the object characteristic value can be reduced. That is, the estimated value can be brought closer to the object characteristic value.

[0202] (If the result is YES: m=Nθ) Execute step S440. In step S440, the estimate is updated.

[0203] The gradient contains information about the difference between the estimate and the object property value, so adding the gradient to the estimate gives an updated estimate.

[0204] The updated estimates are closer to the object property values ​​than the initial values, and can therefore be used to update the values ​​of the three-dimensional optical properties of the estimated object 24.

[0205] In step S450, TV regularization is performed.

[0206] By performing TV regularization, noise can be removed and blurred images can be corrected. TV regularization can be performed as necessary. Therefore, step S450 may be omitted.

[0207] In step S463, it is determined whether the value of the variable i coincides with the value of the number of iterations N(n). If the result of the determination is NO, step S464 is executed. If the result of the determination is YES, step S465 is executed.

[0208] (If the result is NO: i ≠ N(n)) Step S464 is executed. In step S464, the value of the variable i is incremented by 1. When step S464 ends, the process returns to step S230.

[0209] In step S464, the value of the variable i is incremented by 1. However, the value of the variable n in the wavefront information W(m,n) does not change. Since the value of the variable n is 1, step S300 is executed again using the first wavefront information. Step S300 is repeated until the value of the variable i matches the value of the iteration number N(n).

[0210] In step S230, the value of the variable m is set to 1. Therefore, steps S400 to S430 are repeated until the value of the variable m matches the number of angle change times Nθ.

[0211] In the above example, when the value of the variable n is 1, the value of the number of iterations N(n) is set to 3. Therefore, step S300 is executed three times. Also, the process in step S410 is the first optimization process. In the above example, step S300 is executed three times, so the first optimization process is executed three times.

[0212] In the first iteration of the first optimization process, the estimated value is updated. The updated estimated value is closer to the object characteristic value than the initial value. In the second iteration of the first optimization process, the updated estimated value is used. As a result, in the second iteration of the first optimization process, the estimated value can be brought closer to the object characteristic value. By executing the first optimization process multiple times, the estimated value can be brought closer to the object characteristic value.

[0213] (If the answer is YES: i = N(n))

[0214] Step S465 is executed. In step S465, it is determined whether the value of the variable n coincides with the value of the number of wavelengths Nλ'. If the result of the determination is NO, step S466 is executed. If the result of the determination is YES, the process ends.

[0215] (If the result is NO: n ≠ Nλ') Step S466 is executed. In step S466, the value of the variable n is incremented by 1. When step S466 is completed, the process returns to step S220.

[0216] In step S466, the value of variable n is incremented by 1. In this case, the value of variable n in wavefront information W(m,n) changes. Because the value of variable n is other than 1, step S300 is executed using the second wavefront information. If the value of variable n is 2, step S300 is executed using the second wavefront information. If the value of variable n is 3, step S300 is executed using the third wavefront information.

[0217] In step S220, the value of the variable i is set to 1. Therefore, step S300 is repeated until the value of the variable i matches the value of the iteration number N(n).

[0218] Also, in step S230, the value of the variable m is set to 1. Therefore, steps S400 to S430 are repeated until the value of the variable m matches the number of angle change times Nθ.

[0219] In the above example, when the value of the variable n is 2, the value of the number of iterations N(n) is set to 2. Therefore, step S300 is executed twice. Also, the process in step S410 is the second optimization process. In the above example, since step S300 is executed twice, the second optimization process is executed twice.

[0220] Before executing the second optimization process, the first optimization process is executed. Therefore, the estimated value updated in the first optimization process is used as the initial value in the second optimization process. The initial value in the second optimization process is closer to the object characteristic value than the initial value in the first optimization process. Therefore, the estimated value can be made closer to the object characteristic value.

[0221] The estimated value is updated in the first second optimization process. The updated estimated value is closer to the object characteristic value than the initial value. The updated estimated value is used in the second second optimization process. As a result, in the second second optimization process, the estimated value can be brought closer to the object characteristic value. By executing the second optimization process multiple times, the estimated value can be brought closer to the object characteristic value.

[0222] Step S300 is repeated until the value of the variable n coincides with the value of the number of wavelengths Nλ'. In the above example, the value of the number of wavelengths Nλ' is set to 3. Therefore, the optimization process is performed three times.

[0223] As described above, the first optimization process is executed once when the value of variable n is 1, and the second optimization process is executed once when the value of variable n is 2. Therefore, when the value of variable n is 3, if the third optimization process is executed, the value of variable n will match the value of the number of wavelengths Nλ'.

[0224] In the above example, the value of λ(1) is set to 1500 nm, the value of λ(2) is set to 650 nm, and the value of λ(3) is set to 480 nm.

[0225] Illumination light with a wavelength of 1500 nm is the first illumination light. The optimization process for this wavelength is the first optimization process when the value of variable n is 1. Illumination light with a wavelength of 650 nm is the second illumination light. The optimization process for this wavelength is the second optimization process when the value of variable n is 2.

[0226] The optimization process when the value of the variable n is 3 is the third optimization process. The third optimization process is an optimization process for a wavelength of 480 nm. Illumination light with a wavelength of 480 nm is the second illumination light. Therefore, the optimization process for a wavelength of 480 nm is the same as the second optimization process. Therefore, a description will be omitted.

[0227] When the value of the variable n is 3, the optimization process can be performed in the following order: (Example 1) First optimization process, second optimization process, third optimization process. (Example 2) First optimization process, third optimization process, second optimization process.

[0228] In the optimization process when the value of the variable n is 3, the process can be performed with the following combinations. (Example 1) First optimization process: Illumination light with a wavelength of 1500 nm. Second optimization process: Illumination light with a wavelength of 650 nm (Example 2) First optimization process: Illumination light with a wavelength of 1500 nm. Second optimization process: Illumination light with a wavelength of 480 nm (Example 3) First optimization process: Illumination light with a wavelength of 650 nm. Second optimization process: Illumination light with a wavelength of 480 nm

[0229] For example, when the wavelengths of wavefront information a and wavefront information b are different, the wavefront information a includes information not included in the wavefront information b, and the wavefront information b includes information not included in the wavefront information a. Therefore, the more wavefront information with different wavelengths there is, the greater the amount of information.

[0230] As the amount of information increases, the corrected wavefront can be calculated more accurately in step S431. As a result, the accuracy of the gradient also increases. The gradient includes information about the difference between the estimated value and the object characteristic value. By increasing the accuracy of the gradient, the difference between the estimated value and the object characteristic value can be reduced. In other words, the estimated value can be made closer to the object characteristic value. Therefore, it is preferable to execute each of the first optimization process and the second optimization process two or more times.

[0231] (If the answer is YES: n=Nλ') Since the preset number of iterations has been reached, the three-dimensional optical characteristics of the estimated object are calculated in step S500, and the process ends.

[0232] As described above, with illumination light having a long wavelength, a large amount of wavefront information can be acquired in the axial direction. A certain amount of wavefront information can also be acquired in the lateral direction. The wavelength of the illumination light used to acquire the first wavefront information is longer than the wavelength of the illumination light used to acquire the second wavefront information. Therefore, by using the first wavefront information, the three-dimensional optical characteristics of the estimation object can be roughly estimated.

[0233] The first wavefront information is used in the first optimization process, so that the three-dimensional optical characteristics of the estimated object can be roughly estimated by performing the first optimization process.

[0234] In step S210, the value of the variable n is set to 1. Therefore, the process in step S410 that is executed first is the first optimization process. In the first optimization process, the three-dimensional optical characteristics of the estimated object can be roughly estimated. Therefore, by executing the first optimization process before the second optimization process, the three-dimensional optical characteristics of the estimated object can be efficiently estimated.

[0235] In the first estimation process, the first optimization process and the second optimization process are each executed two or more times. This makes it possible to prevent a decrease in resolution and a decrease in estimation accuracy. As a result, it is possible to realize an estimation device that can acquire the three-dimensional optical characteristics of an object with high accuracy and high resolution even if the object is thick.

[0236] In the estimation device of the present embodiment, it is preferable that the processor continuously executes a first optimization process for the initial values ​​set for the three-dimensional optical properties.

[0237] As described above, step S150 can be provided as necessary. When step S150 is provided, an initial value is set to the estimated value of the three-dimensional optical characteristic. In this case, the first optimization process is continuously performed on the initial value set to the three-dimensional optical characteristic.

[0238] In the estimation device of this embodiment, the estimation process includes a first optimization process using the first wavefront information as a constraint condition and a second optimization process using the second wavefront information as a constraint condition, and the processor executes a combined process consisting of the first optimization process and the second optimization process two or more times, and it is preferable that in the combined process, the first optimization process is executed first and that in the combined process, after the second optimization process is executed, the first optimization process is not executed.

[0239] 9 is a flowchart of the second estimation process. The same steps as those in the first estimation process are given the same numbers, and the description thereof will be omitted.

[0240] The following describes the combined processing. Therefore, the combined processing is described as being started from the beginning. However, the combined processing may be started after a specific optimization process such as the first optimization process or the second optimization process is executed a predetermined number of times.

[0241] The second estimation process includes a composite process, which includes a first optimization process and a second optimization process, and which is executed two or more times.

[0242] To repeat the composite process, the second estimation process includes steps S141, S142, S201, S467, S468, and S469.

[0243] When, for example, 1500 nm and 650 nm are selected as the wavelength λ(n), the value of the wavelength λ(n) is set as follows: Value of λ(1): 1500 nm Value of λ(2): 650 nm

[0244] In the above example, since the number of selected wavelengths is 2, the value of the number of wavelengths Nλ′ is set to 2.

[0245] In step S141, a first iteration number NS is set. The first iteration number NS is the number of times the composite process is executed. For example, when the composite process is executed twice, the value of the first iteration number NS is set to 2.

[0246] In step S142, a second iteration number N(n,j) is set. The second iteration number N(n,j) is the number of times the optimization process is executed.

[0247] The variable n is used for the second iteration number N(n,j) and the wavelength λ(n). Therefore, when setting the second iteration number N(n,j), the iteration number is set for the value (wavelength) set for the wavelength λ(n).

[0248] The number of times the optimization process is performed can be changed for each composite process. Therefore, the second number of iterations N(n,j) is set to a number for each composite process.

[0249] In the above example, the number of selected wavelengths is 2. Also, the number of times the composite process is executed is 4. The value of the second iteration number N(n,j) is set, for example, as follows: Value of N(1,1): 5 times Value of N(2,1): 1 time Value of N(1,2): 5 times (continue to be 5 times) Value of N(2,2): 1 time Value of N(1,3): 3 times (reduced from 5 times to 3 times) Value of N(2,3): 1 time Value of N(1,4): 3 times (continues to be 3 times) N(2,4) value: 1 time Value of N(1,4): 1 time (reduced from 3 times to 1 time) N(2,4) value: 1 time

[0250] In the above example, the number of times the first optimization process has been performed is greater than or equal to the number of times the second optimization process has been performed. The difference between the number of times the second optimization process has been performed and the number of times the first optimization process has been performed is reduced. After the composite process is continuously performed, the difference between the number of times the second optimization process has been performed and the number of times the first optimization process has been performed is reduced.

[0251] By increasing the number of second optimization processes, the difference between the first optimization process and the second optimization process in the combined process may be reduced.

[0252] In step S201, the value of the variable j is set to 1.

[0253] Since the value of the variable j is 1, the first composite process is executed. Also, in step S210, the value of the variable n is set to 1. Therefore, in the process in the first step S300, the first optimization process is executed.

[0254] In step S467, it is determined whether the value of the variable i coincides with the value of the second iteration number N(n,j). If the result of the determination is NO, step S464 is executed. If the result of the determination is YES, step S465 is executed.

[0255] (If the result is NO: i ≠ N(n,j)) Step S464 is executed. In step S464, the value of the variable i is incremented by 1. When step S464 ends, the process returns to step S230.

[0256] In step S464, the value of the variable i is incremented by 1. However, the value of the variable n does not change, so the value of the variable n is 1. Therefore, in the process in S300, the first optimization process is executed again. The first optimization process is repeated until the value of the variable i matches the value of the iteration count N(n).

[0257] Since the value of variable j does not change, the value of variable j is 1. In the above example, when the value of variable n is 1 and the value of variable j is 1, the value of the second iteration number N(n,j) is set to 3. Therefore, the first optimization process is executed three times.

[0258] (If the answer is YES: i=N(n,j)) Step S465 is executed. In step S465, it is determined whether the value of the variable n coincides with the value of the number of wavelengths Nλ'. If the result of the determination is NO, step S466 is executed. If the result of the determination is YES, step S468 is executed.

[0259] (If the result is NO: n ≠ Nλ') Step S466 is executed. In step S466, the value of the variable n is incremented by 1. When step S466 is completed, the process returns to step S220.

[0260] In step S466, the value of the variable n is incremented by 1. In this case, since the value of the variable n is other than 1, the second optimization process is executed in the process in S300.

[0261] In step S220, the value of the variable i is set to 1. Therefore, the second optimization process is repeated until the value of the variable i matches the value of the second iteration number N(n,j).

[0262] The value of variable n changes from 1 to 2. The value of variable j does not change, so the value of variable j is 1. In the above example, when the value of variable n is 2 and the value of variable j is 1, the value of the second iteration number N(n,j) is set to 2. Therefore, the second optimization process is executed twice.

[0263] (If the answer is YES: n=Nλ') Step S468 is executed. In step S468, it is determined whether the value of the variable j coincides with the value of the first iteration number NS. If the result of the determination is NO, step S469 is executed. If the result of the determination is YES, the process is terminated.

[0264] (If the result is NO: n ≠ NS) Step S469 is executed. In step S468, the value of variable j is incremented by 1. When step S468 is completed, the process returns to step S210.

[0265] In step S466, the value of variable j is incremented by 1. Since the value of variable j is 2, a second composite process is executed.

[0266] In step S210, the value of the variable n is set to 1. Therefore, the first optimization process is executed. In step S220, the value of the variable i is set to 1. Therefore, the second optimization process is repeated until the value of the variable i matches the value of the second iteration number N(n,j).

[0267] The value of variable n is 1, and the value of variable j is 2. In the above example, when the value of variable n is 2 and the value of variable j is 1, the value of the second iteration number N(n,j) is set to 1. Therefore, the first optimization process is executed once.

[0268] When the first optimization process is completed, the value of the variable n changes from 1 to 2. Therefore, the second optimization process is executed. In step S220, the value of the variable i is set to 1. Therefore, the second optimization process is repeated until the value of the variable i matches the value of the second iteration number N(n,j).

[0269] The value of variable n is 2, and the value of variable j is 2. In the above example, when the value of variable n is 2 and the value of variable j is 2, the value of the second iteration number N(n,j) is set to 4. Therefore, the second optimization process is executed four times.

[0270] (If the result is YES: n=NS') Since the preset number of iterations has been reached, the three-dimensional optical characteristics of the estimated object are calculated in step S500, and the process ends.

[0271] As described above, in the second estimation process, the composite process is executed two or more times. In this case, the first optimization process and the second optimization process are executed alternately. This makes it possible to prevent a decrease in resolution and a decrease in estimation accuracy. As a result, it is possible to provide an estimation device, an estimation system, an estimation method, and a recording medium that can acquire the three-dimensional optical characteristics of an object with high accuracy and high resolution even when the object is thick.

[0272] In the estimation device of the present embodiment, it is preferable that the processor executes composite processing on the initial values ​​set for the three-dimensional optical characteristics.

[0273] As described above, step S150 can be provided as necessary. When step S150 is provided, an initial value is set to the estimated value of the three-dimensional optical characteristic. In this case, the composite process is performed on the initial value set to the three-dimensional optical characteristic.

[0274] In the estimation device of this embodiment, it is preferable that the composite process be controlled so that the number of times the first optimization process is executed is equal to or greater than the number of times the second optimization process is executed.

[0275] As described above, the first optimization process is performed to roughly estimate the three-dimensional optical characteristics of the estimated object. Therefore, the three-dimensional optical characteristics of the estimated object can be roughly estimated efficiently by using the first wavefront information more times than the second wavefront information.

[0276] When step S150 is provided, in the first estimation process and the second estimation process, an initial value is set for the estimation value in step S150. The initial value is different from the object characteristic value. Therefore, by executing the first optimization process as soon as possible, the estimation value can be made closer to the object characteristic value. As a result, efficient estimation can be achieved.

[0277] In the estimation device of this embodiment, a predetermined process is executed in a composite process. In the predetermined process, the first optimization process is executed more times than the second optimization process. Also, the first optimization process is executed before the second optimization process. Therefore, the three-dimensional optical characteristics of the estimation object can be efficiently estimated.

[0278] In the estimation device of this embodiment, it is preferable that control continues in successive composite processes.

[0279] In the estimation device of this embodiment, after the composite process has been executed a predetermined number of times, it is preferable that the composite process be controlled to reduce the difference between the number of times the second optimization process has been executed and the number of times the first optimization process has been executed.

[0280] In the estimation device of this embodiment, a predetermined process is executed in the second composite process. In the predetermined process, the first optimization process is executed more times than the second optimization process. Also, the first optimization process is executed before the second optimization process. Therefore, the three-dimensional optical characteristics of the estimation object can be efficiently estimated.

[0281] In the estimation device of this embodiment, it is preferable that the first illumination light is light in the infrared region, and the second illumination light is light in the visible region.

[0282] According to the estimation device of this embodiment, the three-dimensional optical characteristics of the estimation object can be efficiently estimated.

[0283] In the estimation device of this embodiment, the first illumination light is light in the infrared region, It is preferable that the following conditional formula (A) be satisfied. 2×λ2<λ1 (A) Where: λ1 is the wavelength of the first illumination light, λ2 is the wavelength of the second illumination light, It is.

[0284] According to the estimation device of this embodiment, the three-dimensional optical characteristics of the estimation object can be efficiently estimated.

[0285] The estimation system of this embodiment includes the estimation device of this embodiment, a light source unit that emits a first illumination light and a second illumination light, a photodetector, a stage on which an object is placed, and an angle changing mechanism. The stage is disposed on an optical path between the light source unit and the photodetector, and the angle changing mechanism changes the incident angle of the first illumination light with respect to the object and the incident angle of the second illumination light with respect to the object.

[0286] Fig. 10 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 1 are given the same numbers and their explanations are omitted.

[0287] The estimation system 30 includes a light source unit 31, a photodetector 34, a stage 35, and an estimation device 1. The estimation device 1 includes a memory 2 and a processor 3.

[0288] The light source unit 31 emits a first illumination light and a second illumination light. In the estimation system 30, the light source unit 31 has a first light source 32 and a second light source 33. The first light source 32 emits the first illumination light. The second light source 33 emits the second illumination light. The longest wavelength in the wavelength band of the second illumination light is located on the shorter wavelength side than the shortest wavelength in the wavelength band of the first illumination light.

[0289] The first illumination light is incident on the dichroic mirror 36 from a first direction. The second illumination light is incident on the dichroic mirror 36 from a direction perpendicular to the first direction.

[0290] The dichroic mirror 36 has a spectral characteristic of transmitting light with a long wavelength and reflecting light with a short wavelength. Therefore, the first illumination light passes through the dichroic mirror 36 and travels in the first direction. The second illumination light is reflected by the dichroic mirror 36 and travels in the first direction.

[0291] A beam splitter 37 is disposed in the first direction. The first illumination light and the second illumination light are incident on the beam splitter 37. The beam splitter 37 has an optical surface on which an optical film is formed. In the beam splitter 37, the optical film generates, from the incident light, light that transmits in the first direction and light that is reflected in the second direction.

[0292] In the estimation system 30, a measurement optical path OP is provided in a first direction. mea and in the second direction, a reference optical path OP ref However, in the first direction, a reference optical path OP ref and in the second direction, a measurement path OP mea The first illumination light and the second illumination light may each be formed into a measurement optical path OP mea and the reference path OP ref will proceed.

[0293] Measurement optical path OP mea A mirror 38 is disposed in the measurement optical path OP mea is folded in a second direction by the mirror 38. ref A mirror 39 is disposed in the reference optical path OP ref is folded in a first direction by the mirror 39. As a result, the reference beam path OP ref is the measurement optical path OP mea A beam splitter 40 is disposed at the location where the two optical paths intersect.

[0294] Measurement optical path OP mea, a stage 35 is disposed between a mirror 38 and a beam splitter 40. An object S is placed on the stage 35. The object S is irradiated with the first illumination light and the second illumination light.

[0295] When the first illumination light is irradiated onto the object S, the first measurement light L mea1 The first measuring light L mea1 is the first illumination light that has passed through the object S. When the second illumination light is irradiated onto the object S, the second measurement light L mea2 The second measuring light L mea2 is the second illumination light that has passed through the object S.

[0296] Reference optical path OP ref Now, the first reference light L ref1 and the second reference light L ref2 The first reference light L ref1 is the first illumination light that does not pass through the object S. The second reference light L ref2 is the second illumination light that does not pass through the object S.

[0297] 1st measurement light L mea1 , second measurement light L mea2 , first reference light L ref1 , and the second reference light L ref2 The light is incident on the beam splitter 40. The beam splitter 40 has an optical surface on which an optical film is formed. In the beam splitter 40, the optical film generates from the incident light a light that transmits in a first direction and a light that is reflected in a second direction.

[0298] A photodetector 34 is disposed in the first direction. When the first light source 32 and the second light source 33 are turned on, the first measurement light L mea1 , second measurement light L mea2 , first reference light L ref1 , and the second reference light L ref2 is incident.

[0299] When the first light source 32 is turned on and the second light source 33 is turned off, the first measurement light L mea1 and the first reference beam L ref1The second measurement light L is incident on the photodetector 34. When the first light source 32 is turned off and the second light source 33 is turned on, the second measurement light L mea2 and the second reference light L ref2 is incident on the photodetector 34.

[0300] 1st measurement light L mea1 and the first reference beam L ref1 The first interference fringes are formed by the second measurement light L mea2 and the second reference light L ref2 Then, a second interference fringe is formed. By capturing an image of the first interference fringe and the second interference fringe with the photodetector 34, an image of the first interference fringe and an image of the second interference fringe can be obtained.

[0301] The first interference fringe image and the second interference fringe image are sent to an estimation device 1. The estimation device 1 acquires first wavefront information based on the first interference fringe image. The estimation device 1 acquires second wavefront information based on the second interference fringe image. The first wavefront information and the second wavefront information are stored in a memory 2. An estimation process is performed using the first wavefront information and the second wavefront information.

[0302] In the estimation process, a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information are used. In the plurality of pieces of first wavefront information, the angle of incidence of the first illumination light on the object is different for each piece of first wavefront information. In the plurality of pieces of second wavefront information, the angle of incidence of the second illumination light on the object is different for each piece of second wavefront information.

[0303] The estimation system of this embodiment has an angle changing mechanism. The angle changing mechanism changes the relative direction. Therefore, it is possible to change the incident angle of the illumination light with respect to the object. As a result, it is possible to obtain a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information.

[0304] In the estimation system of this embodiment, the angle change mechanism has a drive device and a rotating member, the rotating member holds the stage, and it is preferable that the rotation axis of the rotating member intersects the object and is perpendicular to the optical axis of the light path.

[0305] As shown in FIG. 10, the estimation system 30 includes an angle changing mechanism 41. The angle changing mechanism 41 changes the measurement optical path OPmea is placed to the side.

[0306] The angle changing mechanism 41 has a driving device 42 and a rotating member 43. The rotating member 43 holds the stage 35. The axis RX is a rotation axis of the rotating member 43. The axis RX intersects with the object S and is perpendicular to the optical axis AX.

[0307] In the angle change mechanism 41, a rotating member 43 is rotated by a driving device 42. The rotating member 43 holds the stage 35, and therefore the stage 35 rotates. By rotating the stage 35, the object S can be rotated about the axis RX.

[0308] The first illumination light and the second illumination light are reflected by the mirror 38 and enter the object S. The orientation of the object S relative to the first illumination light and the orientation of the object S relative to the second illumination light change as the object S rotates. Thus, the first illumination light and the second illumination light are irradiated onto the object S from various directions.

[0309] First measurement light L from object S mea1 and the second measurement light L mea2 The first measuring light L mea1 and the second measurement light L mea2 is incident on the photodetector 34.

[0310] In the estimation system 30, the direction of the first illumination light and the direction of the second illumination light remain unchanged, but the direction of the object S changes. Therefore, the incidence angle of the first illumination light with respect to the object S and the incidence angle of the second illumination light with respect to the object S can be changed.

[0311] In the estimation system of the present embodiment, it is preferable that the angle changing mechanism has a drive device and a rotating member, the rotating member has a reflective surface, and the orientation of the reflective surface changes by changing the arrangement angle of the rotating member.

[0312] Fig. 11 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 10 are given the same numbers and their explanations are omitted.

[0313] The estimation system 50 includes an angle change mechanism 60 and an angle change mechanism 70. The angle change mechanism 60 and the angle change mechanism 70 change the measurement optical path OP mea are located at.

[0314] The angle-changing mechanism 60 has a driving device 61 and a rotating member 62. The rotating member 62 has a reflective surface. The orientation of the reflective surface changes due to the rotational motion or reciprocal motion of the rotating member 62. The angle-changing mechanism 70 has a driving device 71 and a rotating member 72. The rotating member 72 has a reflective surface. The orientation of the reflective surface changes due to the rotational motion or reciprocal motion of the rotating member 72.

[0315] The angle changing mechanism 60 is, for example, a galvanometer scanner or a polygon scanner. In a galvanometer scanner, the orientation of the reflective surface is changed by the repetitive motion of a plane mirror. In a polygon scanner, the orientation of the reflective surface is changed by the rotational motion of a polygon mirror. Galvanometer scanners and polygon scanners are called optical deflectors.

[0316] Between the angle changing mechanism 60 and the angle changing mechanism 70, there are disposed an illumination optical system 51, a stage 35, and a detection optical system 52. The object S is located between the illumination optical system 51 and the detection optical system 52.

[0317] The first illumination light and the second illumination light pass through the illumination optical system 51 and are incident on the object S. The direction of the first illumination light with respect to the object S and the direction of the second illumination light with respect to the object S change due to the rotational motion or reciprocating motion of the rotating member 62. Thus, the first illumination light and the second illumination light are irradiated onto the object S from various directions.

[0318] First measurement light L from object S mea1 and the second measurement light L mea2 The first measuring light L mea1 and the second measurement light L mea2 passes through the detection optical system 52 and enters the angle changing mechanism 70.

[0319] The first measurement light L with respect to the angle changing mechanism 70mea1 The incident angle of the second measurement light L with respect to the angle changing mechanism 70 is changed. mea2 The incident angle of the first measuring light L also changes. The change in the incident angle can be counteracted by the angle changing mechanism 70. mea1 and the second measurement light L mea2 The first measurement light L is incident on the mirror 53 without moving. mea1 and the second measurement light L mea2 is incident on the photodetector 34.

[0320] In the estimation system 50, the direction of the illumination light is changed by the angle changing mechanism 60. In this case, the direction of the first illumination light and the direction of the second illumination light are changed without changing the direction of the object S. Therefore, the incidence angle of the first illumination light with respect to the object S and the incidence angle of the second illumination light with respect to the object S can be changed.

[0321] In the estimation system 50, the rotational movement of the rotating member or the reciprocal movement of the rotating member is performed in one axis. However, the rotational movement of the rotating member or the reciprocal movement of the rotating member may be performed in two orthogonal axes.

[0322] In the estimation system 30 and the estimation system 50, the number of illumination lights is 2 and the number of photodetectors is 1. Therefore, it is necessary to switch the illumination light.

[0323] Fig. 12 is a diagram showing a method for switching illumination light. The same components as in Fig. 10 are given the same numbers and description will be omitted. Fig. 12(a) is a diagram showing a first switching method. Fig. 12(b) is a diagram showing a second switching method. Fig. 12(c) is a diagram showing a third switching method.

[0324] (First Method) 12(a), the first method uses a first light-shielding plate 80 and a second light-shielding plate 81. The first light source 32 and the second light source 33 are turned on. The first light source 32 emits a first illumination light, and the second light source 33 emits a second illumination light.

[0325] A first light-shielding plate 80 is disposed outside the optical path between the first light source 32 and the dichroic mirror 36. A second light-shielding plate 81 is disposed outside the optical path between the second light source 33 and the dichroic mirror 36. The first light-shielding plate 80 and the second light-shielding plate 81 are capable of being inserted into and removed from the optical path.

[0326] With the first light-shielding plate 80 positioned outside the optical path, the second light-shielding plate 81 is inserted between the second light source 33 and the dichroic mirror 36. With this arrangement, the first illumination light can be selected.

[0327] With the second light-shielding plate 81 positioned outside the optical path, the first light-shielding plate 80 is inserted between the first light source 32 and the dichroic mirror 36. With this arrangement, the second illumination light can be selected.

[0328] (Second Method) 12(b), the second method uses a first optical filter 82 and a second optical filter 83. The light source unit 31 is turned on. The light source unit 31 has one light source. The first illumination light and the second illumination light are emitted from the one light source.

[0329] A first optical filter 82 and a second optical filter 83 are disposed outside the optical path between the light source unit 31 and the beam splitter 37. The first optical filter 82 and the second optical filter 83 are capable of being inserted into and removed from the optical path.

[0330] The first optical filter 82 has a spectral characteristic of transmitting only the first illumination light, and the second optical filter 83 has a spectral characteristic of transmitting only the second illumination light.

[0331] With the second optical filter 83 positioned outside the optical path, the first optical filter 82 is inserted between the light source unit 31 and the beam splitter 37. With this arrangement, the first illumination light can be selected.

[0332] With the first optical filter 82 positioned outside the optical path, the second optical filter 83 is inserted between the light source unit 31 and the beam splitter 37. With this arrangement, the second illumination light can be selected.

[0333] As shown in FIG. 12( a ), when the light source unit 3 has two light sources, a first optical filter 82 and a second optical filter 83 can be inserted and removed between the dichroic mirror 36 and the beam splitter 37 .

[0334] (Third Method) 12(c), the third method uses a first optical filter 82 and a second optical filter 83. The first light source 32 and the second light source 33 are turned on.

[0335] A first optical filter 82 and a second optical filter 83 are disposed outside the optical path between the beam splitter 40 and the photodetector 34. The first optical filter 82 and the second optical filter 83 are capable of being moved in and out of the optical path.

[0336] With the second optical filter 83 positioned outside the optical path, the first optical filter 82 is inserted between the beam splitter 40 and the photodetector 34. With this arrangement, the first illumination light can be selected.

[0337] With the first optical filter 82 positioned outside the optical path, the second optical filter 83 is inserted between the beam splitter 40 and the photodetector 34. With this arrangement, the second illumination light can be selected.

[0338] It is preferable that the estimation system of this embodiment includes a photodetector separate from the photodetector, the photodetector having a sensitivity equal to or greater than a first threshold value to the wavelength band of the first illumination light and not having a sensitivity equal to or greater than the first threshold value to the wavelength band of the second illumination light, and the other photodetector having a sensitivity equal to or greater than a second threshold value to the wavelength band of the second illumination light and not having a sensitivity equal to or greater than the second threshold value to the wavelength band of the first illumination light.

[0339] Fig. 13 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 11 are given the same numbers and their explanations are omitted.

[0340] The estimation system 90 includes a first photodetector 91 and a second photodetector 92. When the first light source 32 and the second light source 33 are turned on, the first photodetector 91 and the second photodetector 92 detect the first measurement light L mea1 , second measurement light L mea2 , first reference light L ref1 , and the second reference light L ref2 is incident.

[0341] The first photodetector 91 has a sensitivity equal to or higher than a first threshold value for the wavelength band of the first illumination light, but does not have a sensitivity equal to or higher than the first threshold value for the wavelength band of the second illumination light. mea1 and the first reference beam L ref1 It is possible to capture only the first interference fringes formed by the first threshold value. The first threshold value may be appropriately determined.

[0342] The second photodetector 92 has a sensitivity equal to or higher than a second threshold value for the wavelength band of the second illumination light, but does not have a sensitivity equal to or higher than the second threshold value for the wavelength band of the first illumination light. mea2 and the second reference light L ref2 It is possible to capture only the second interference fringes formed by the second threshold value. The second threshold value may be appropriately determined.

[0343] The estimation system of this embodiment preferably includes a photodetector separate from the photodetector, a first optical element used together with the photodetector, and a second optical element used together with the separate photodetector, and the first optical element has a property of transmitting the first illumination light and blocking the second illumination light, and the second optical element has a property of transmitting the second illumination light and blocking the first illumination light.

[0344] Fig. 14 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 11 are given the same numbers and their explanations are omitted.

[0345] The estimation system 100 includes a first photodetector 101, a second photodetector 102, a first optical element 103, and a second optical element 104.

[0346] The first optical element 103 is disposed between the beam splitter 40 and the first photodetector 101. The second optical element 104 is disposed between the beam splitter 40 and the second photodetector 102.

[0347] When the first light source 32 and the second light source 33 are turned on, the first optical element 103 and the second optical element 104 receive the first measurement light L mea1 , second measurement light L mea2 , first reference light L ref1 , and the second reference light L ref2 is incident.

[0348] The first optical element 103 has a property of transmitting the first illumination light and blocking the second illumination light. mea1 and the first reference beam L ref1 The first measuring light L mea1 and the first reference beam L ref1 Thus, first interference fringes are formed. By capturing an image of the first interference fringes with the first photodetector 101, an image of the first interference fringes can be obtained.

[0349] The first optical element 104 has a property of transmitting the second illumination light and blocking the first illumination light. mea2 and the second reference light L ref2 The second measurement light L is incident on the second photodetector 102. mea2 and the second reference light L ref2 Then, second interference fringes are formed. By capturing an image of the second interference fringes with the second photodetector 102, an image of the second interference fringes can be obtained.

[0350] Fig. 15 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 10 are given the same numbers and will not be described.

[0351] The estimation system 110 includes a mirror 111 and a beam splitter 112. The mirror 111 is connected to a measurement optical path OP mea The beam splitter 112 is disposed in the reference optical path OP ref and measurement optical path OP mea are located at the intersection.

[0352] In the estimation system 30 shown in FIG. 10, a beam splitter 40 separates the measurement optical path OP mea is bent in the first direction and the reference optical path OP ref is bent in a first direction.

[0353] In contrast, in the estimation system 110, the mirror 111 is used to mea is bent in the opposite direction to the first direction, and a reference optical path OP ref is bent in the opposite direction to the first direction. mea and the reference optical path OP ref A difference occurs between the optical path length of

[0354] When the coherence length of the illumination light is longer than the difference in the optical path lengths, interference fringes are formed. When the coherence length of the illumination light is shorter than the difference in the optical path lengths, the optical path length adjustment unit 113 is disposed between the beam splitter 37 and the mirror 112. By disposing in this manner, interference fringes can be formed.

[0355] The optical path length adjustment unit 113 has, for example, a piezo stage and four mirrors. Two mirrors are placed on the piezo stage. By moving the two mirrors, the reference optical path OP ref The optical path length in the light source can be changed by driving the piezo stage in steps equal to or smaller than the wavelength of the light source, and the wavefront information can be calculated by taking images multiple times.

[0356] The estimation system of this embodiment includes the estimation device of this embodiment and a light source unit that emits first illumination light and second illumination light. The light source unit is composed of multiple independent light sources with different illumination angles, and is characterized in that a processor of the estimation device or a processor different from the processor controls whether or not to cause the light source to emit illumination light, thereby changing the angle of incidence of the first illumination light to the object and the angle of incidence of the second illumination light to the object.

[0357] Fig. 16 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 11 are given the same numbers and their explanations are omitted.

[0358] The estimation system 120 includes a light source 121, a lens 122, a lens 123, and a photodetector 124. The lens 123 is disposed in the illumination optical system 51. In the estimation system 120, a measurement optical path OP mea Only one is formed.

[0359] The light source 121 has a first illumination section and a second illumination section. Each of the first illumination section and the second illumination section has a plurality of light emitting sections. For example, a light emitting diode (LED) or a semiconductor laser (LD) can be disposed in the light emitting section.

[0360] The light emitting units are arranged in an array. The light emitting units can independently control light emission and extinction. The first illumination unit emits a first illumination light. The second illumination unit emits a second illumination light.

[0361] The light emitting portion may be an emission surface of a fiber bundle. The fiber bundle has a first fiber bundle and a second fiber bundle. By connecting the first fiber bundle to a first light source (not shown), a first illumination light is emitted from the emission surface of the first fiber bundle. By connecting the second fiber bundle to a second light source (not shown), a second illumination light is emitted from the emission surface of the second fiber bundle.

[0362] It is preferable that the object S is illuminated with parallel light. In the light source 121, the area of ​​the light exit portion is small enough that it can be regarded as a point light source. Therefore, the light exit portion is disposed at a position conjugate with the pupil position of the illumination optical system 51.

[0363] The lens 122 is disposed between the light source 121 and the illumination optical system 51. The lens 122 and the lens 123 can make the position of the light source 121 conjugate with the pupil position of the illumination optical system 51. When a sufficient space can be secured around the pupil position of the illumination optical system 51, the light emitting unit may be disposed at the pupil position of the illumination optical system 51.

[0364] In the light source 121, the first illumination unit and the second illumination unit are controlled. In this control, the light emitting unit from which light is emitted is changed among the multiple light emitting units. By this control, it is possible to change the incidence angle of the first illumination light with respect to the object and the incidence angle of the second illumination light with respect to the object.

[0365] When the light source 121 is regarded as a light source unit, the first illumination light and the second illumination light are emitted from the light source unit. The first illumination unit and the second illumination unit each have a plurality of light emitting units. Therefore, the light source unit is composed of a plurality of independent light sources with different illumination angles.

[0366] The estimation device 120 has a processor or a processor different from the processor. Therefore, the processor can control the light source unit to emit or not emit illumination light. This control can change the incidence angle of the first illumination light to the object and the incidence angle of the second illumination light to the object.

[0367] In the estimation system 120, since the number of optical paths is only one, phase information cannot be obtained directly from the interference fringes.

[0368] For this reason, the estimation system 120 measures amplitude data of the wavefront. The wavefront to be measured is the wavefront at the detection plane of the photodetector 124. The measurement of the amplitude data of the wavefront may be performed using a plurality of wavelengths or by changing the illumination angle. In the measurement by changing the illumination angle, the illumination angle is changed by a small angle. By using these measurement methods, a data set required for estimating the phase of the wavefront at the detection plane can be measured.

[0369] The estimation system 120 does not require a reference optical path, and therefore the configuration can be made simpler.

[0370] Fig. 17 is a diagram showing images of an object. Fig. 17(a) is an image estimated using the first wavefront information. Fig. 17(b) is an image estimated using the second wavefront information. Fig. 17(c) is an image estimated using the first wavefront information and the second wavefront information. The images are images obtained by simulation.

[0371] In the simulation, a photonic crystal fiber (hereinafter, referred to as a "PCF") is used as the object. The PCF has a cylindrical member and a through hole.

[0372] In the PCF, multiple through holes are formed inside a cylindrical member. The through holes are cylindrical and are formed along the generatrix of the cylindrical member. The outer diameter of the PCF is 230 μm, and the refractive index of the medium is 1.47. The through holes and the cylindrical member are filled with a liquid with a refractive index of 1.44.

[0373] The image shown in Fig. 17(a) was estimated using wavefront information acquired with illumination light having a wavelength λ of 633 nm, while the image shown in Fig. 17(b) was estimated using wavefront information acquired with illumination light having a wavelength λ of 1300 nm.

[0374] The longest wavelength in the wavelength band of the second illumination light is located on the shorter wavelength side than the shortest wavelength in the wavelength band of the first illumination light. Therefore, wavefront information acquired with the second illumination light, i.e., the second wavefront information, is used to estimate the image shown in Fig. 17(a). Wavefront information acquired with the first illumination light, i.e., the first wavefront information, is used to estimate the image shown in Fig. 17(b).

[0375] As described above, the second wavefront information has a smaller amount of wavefront information in the axial direction than the first wavefront information. Therefore, as shown in Fig. 17(a), the structure of the PCF cannot be estimated very well. In contrast, the first wavefront information has a larger amount of wavefront information in the axial direction than the second wavefront information. Therefore, as shown in Fig. 17(b), the structure of the PCF can be roughly estimated. The image shown in Fig. 17(c) is estimated using wavefront information acquired with illumination light having a wavelength λ1 of 1300 nm and wavefront information acquired with illumination light having a wavelength λ2 of 633 nm. Thus, the image shown in Fig. 17(c) is estimated using the first wavefront information and the second wavefront information.

[0376] The second wavefront information has a larger amount of wavefront information in the horizontal direction than the first wavefront information. Therefore, by using the first wavefront information and the second wavefront information for estimation, the accuracy of the estimation can be improved. In an image estimated using the first wavefront information and the second wavefront information, the structure of the PCF in the horizontal direction can be made clearer, as shown in FIG. 17(c).

[0377] Fig. 18 shows images of an object. Fig. 18(a) and Fig. 18(b) are images estimated using the first wavefront information. Fig. 18(c) and Fig. 18(d) are images estimated using the first wavefront information and the second wavefront information. The images are images obtained by simulation.

[0378] The image shown in Fig. 18(a) and the image shown in Fig. 18(c) are estimated using wavefront information acquired by a detection optical system with a numerical aperture NA of 0.1. The image shown in Fig. 18(b) and the image shown in Fig. 18(d) are estimated using wavefront information acquired by a detection optical system with a numerical aperture NA of 0.2.

[0379] Increasing the numerical aperture (NA) of an optical system improves the resolution. Better resolution increases the amount of wavefront information. With more wavefront information, the 3D optical properties of an object can be estimated with greater accuracy.

[0380] In the estimation of the image shown in Fig. 18(b), more wavefront information can be used than in the estimation of the image shown in Fig. 18(a). Therefore, the structure of the PCF is clearer in the image shown in Fig. 18(b) than in the image shown in Fig. 18(a).

[0381] In the estimation of the image shown in Fig. 18(d), more wavefront information can be used than in the estimation of the image shown in Fig. 18(c), and therefore the structure of the PCF is clearer in the image shown in Fig. 18(d) than in the image shown in Fig. 18(c).

[0382] The image shown in Fig. 18(a) and the image shown in Fig. 18(b) are estimated using wavefront information acquired with illumination light having a wavelength λ of 1300 nm. The image shown in Fig. 18(c) and the image shown in Fig. 18(d) are estimated using wavefront information acquired with illumination light having a wavelength λ1 of 1300 nm and wavefront information acquired with illumination light having a wavelength λ2 of 633 nm.

[0383] Increasing the number of wavelengths increases the amount of wavefront information. With more wavefront information, the 3D optical properties of an object can be estimated with higher accuracy. In the estimation of the image shown in Figure 18(c) and the estimation of the image shown in Figure 18(d), wavefront information acquired at wavelengths shorter than 1300 nm is used.

[0384] Illumination light with a short wavelength has a higher resolution than illumination light with a long wavelength, so more information can be used for estimation than wavefront information obtained with illumination light of 1300 nm.

[0385] In the estimation of the image shown in Fig. 18(c), more wavefront information can be used than in the estimation of the image shown in Fig. 18(a). Therefore, the structure of the PCF is clearer in the image shown in Fig. 18(c) than in the image shown in Fig. 18(a).

[0386] In the estimation of the image shown in Fig. 18(d), more wavefront information can be used than in the estimation of the image shown in Fig. 18(b), and therefore the structure of the PCF is clearer in the image shown in Fig. 18(d) than in the image shown in Fig. 18(b).

[0387] The estimation system of this embodiment includes the estimation device of this embodiment, a light source unit that emits first illumination light and second illumination light, an imaging optical system that forms an optical image of an object, a photodetector that acquires an image of the object from the optical image of the object, and a drive mechanism that changes the distance between the focal position of the imaging optical system and the position of the object in the optical axis direction of the imaging optical system. The illumination by the first illumination light and the illumination by the second illumination light form spatial partial coherent illumination for the object.

[0388] Fig. 19 is a diagram showing an estimation system of this embodiment. The same components as those in Fig. 11 are given the same numbers and their explanations are omitted.

[0389] The estimation system 130 includes a light source unit 31, an illumination optical system 133, an aperture member 134, an imaging optical system 135, a photodetector 136, a drive mechanism 137, and an estimation device 1. The estimation device 1 includes a memory 2 and a processor 3.

[0390] The light source unit 31 emits a first illumination light and a second illumination light. In the estimation system 130, the light source unit 31 has a first light source 131 and a second light source 132. The first light source 131 emits the first illumination light. The second light source 132 emits the second illumination light. The first illumination light and the second illumination light are preferably quasi-monochromatic light. Quasi-monochromatic light is light with a narrow wavelength band. For example, LEDs (light-emitting diodes) can be used for the first light source 131 and the second light source 132.

[0391] Instead of the LED, a light source that emits light with a wide wavelength band can be used. In this case, two narrow-band optical filters can be inserted and removed between the dichroic mirror 138 and the illumination optical system 133. For example, the two narrow-band optical filters can be the first optical filter 82 and the second optical filter 83 shown in Fig. 12(b). The spectral transmittance characteristics of the narrow-band optical filters do not need to be highly accurate.

[0392] The light emitted from the first light source 131 can be infrared light, and the light emitted from the second light source 132 can be visible light.

[0393] The first illumination light and the second illumination light are incident on the dichroic mirror 138. The dichroic mirror 138 has a spectral characteristic of transmitting light with a long wavelength and reflecting light with a short wavelength. Therefore, the first illumination light is transmitted through the dichroic mirror 138, and the second illumination light is reflected by the dichroic mirror 138.

[0394] The first illumination light and the second illumination light are incident on the illumination optical system 133. The illumination optical system 133 illuminates the object S.

[0395] An aperture member 134 is disposed in the illumination optical system 133. The aperture member 134 has a circular light-shielding portion 134a, a ring-shaped light-transmitting portion 134b, and a ring-shaped light-shielding portion 134c. The light-transmitting portion 134b may be a light-reducing portion.

[0396] An aperture member other than the aperture member 134 may be prepared and two aperture members may be used. In the other aperture member, the transmitting portion is the same as the transmitting portion 134b, and the two light blocking portions are the same as the light blocking portion 134a and the light blocking portion 134c. However, in the aperture member 134, the first optical filter 82 is provided in the transmitting portion 134b. In the other aperture member, the second optical filter 83 is provided in the transmitting portion.

[0397] When two aperture members are used, it is not necessary to insert and remove two narrow-band optical filters between the dichroic mirror 138 and the illumination optical system 133 .

[0398] An image of the light emitting portion of the first light source 131 and an image of the light emitting portion of the second light source 132 are formed on the aperture member 134. The first light source 131 and the second light source 132 are surface light sources. In a surface light source, the light emitting portion is formed of an infinite number of point light sources. It can be considered that an infinite number of point light sources are located on the aperture member 134.

[0399] In the aperture member 134, the first illumination light and the second illumination light are emitted from the image of the point light source formed in the transmitting portion 134b. However, the first illumination light and the second illumination light are not emitted from the image of the point light source formed in the light-shielding portion 134a and the light-shielding portion 134c. Therefore, the illumination by the first illumination light and the illumination by the second illumination light are partial coherent illumination.

[0400] Partial coherent illumination is intermediate between coherent illumination and incoherent illumination. Coherent illumination is illumination using light emitted from a point light source, such as laser light. Incoherent illumination is illumination using light emitted from a surface light source, such as a halogen lamp.

[0401] Even if the light source is a surface light source, it becomes closer to a point light source by narrowing the area from which the light is emitted. The light source in partial coherent lighting is an intermediate light source between a surface light source and a point light source.

[0402] The aperture member 134 is disposed at the front focal position of the lens 133a. Therefore, a parallel light beam is emitted from the illumination optical system 133. The object S is illuminated with the parallel light.

[0403] The imaging optical system 135 forms an optical image of the object S. The optical image is captured by the photodetector 136, whereby an image of the object S can be obtained. The photodetector 136 can be a two-dimensional sensor, for example, a CCD or a CMOS.

[0404] Two photodetectors may be used, as in the estimation system 100 shown in Fig. 14. In this case, a Si sensor may be used for one photodetector, and an InGaAs sensor may be used for the other photodetector.

[0405] The driving mechanism 137 changes the distance between the focal position of the imaging optical system 135 and the position of the object S in a direction parallel to the optical axis AX. In the estimation system 130, a stage is used for the driving mechanism 137. In this case, the stage is moved in a direction parallel to the optical axis AX while the imaging optical system 135 is fixed. As a result, the position of the object S can be changed with respect to the focal position of the imaging optical system 135.

[0406] Instead of moving the stage, the imaging optical system 135 and the photodetector 136 may be moved in a direction parallel to the optical axis AX. This method also allows the position of the object S to be changed relative to the focal position of the imaging optical system 135.

[0407] In the imaging optical system 135, an infinity corrected microscope objective lens can be used for the lens 135a. In this case, parallel light is emitted from the lens 135a. Therefore, only the lens 135a may be moved in a direction parallel to the optical axis AX.

[0408] An image of the object S is acquired while changing the distance between the focal position of the imaging optical system 135 and the position of the object S. As a result, a plurality of images can be acquired. A plurality of pieces of wavefront information can be acquired from the plurality of images. The plurality of pieces of wavefront information includes axial information for each of the first illumination light and the second illumination light.

[0409] The transmitting portion 134b does not include the optical axis AX. Therefore, the object S is illuminated with parallel light from a direction intersecting the optical axis AX. As a result, an image of the object having contrast can be acquired. Furthermore, since partial coherent illumination is performed, an image of the object can be acquired with higher resolution than with coherent illumination.

[0410] The estimation system 130 uses one aperture member. However, multiple aperture members can be used. By changing the size of the light blocking portion 134a and the width of the annular transmission portion 134, different wavefront information can be obtained.

[0411] Fig. 20 is a diagram showing an image of an aperture member and an object. Fig. 20(a) is a diagram showing an image of a first aperture member and an object. Fig. 20(b) is a diagram showing an image of a second aperture member and an object. Fig. 20(c) is a diagram showing an image of a third aperture member and an object. The images are images obtained by simulation.

[0412] The first aperture member, the second aperture member, and the third aperture member each have a ring-shaped transmitting portion. The position and width of the transmitting portion are different for each aperture member. Therefore, the wavefront information is different for each aperture member.

[0413] The wavefront information obtained from the captured image contains information related to spatial frequency. As the transmission part moves away from the center, the angle of incidence of the illumination light on the object increases. When the angle of incidence increases, the amount of information in the high frequency components becomes more than the information in the low frequency components. When there is more information in the high frequency components, the image of the object emphasizes the fine structure.

[0414] The transmitting parts are farther from the center in the order of the first aperture member, the second aperture member, and the third aperture member. Therefore, in the image of the object, the detailed structure becomes clearer in the order of the image shown in Figure 20(a), the image shown in Figure 20(b), and the image shown in Figure 20(c).

[0415] As described above, a large amount of wavefront information can be acquired by the estimation system 130. Therefore, even if the object has a large thickness, the three-dimensional optical characteristics of the object can be acquired with high accuracy and high spatial resolution.

[0416] The estimation method of this embodiment is a method for estimating three-dimensional optical characteristics of an object. The three-dimensional optical characteristics are a refractive index distribution or an absorptivity distribution. The first wavefront information is wavefront information acquired based on a first illumination light that has passed through the object, and the second wavefront information is wavefront information acquired based on a second illumination light that has passed through the object. The wavelength of maximum intensity in the second illumination light is located on the shorter wavelength side than the wavelength of maximum intensity in the first illumination light. The estimation process is performed using both the first wavefront information and the second wavefront information.

[0417] The estimation process is executed by a computer. The computer reads out the first wavefront information and the second wavefront information stored in a memory and executes the estimation process.

[0418] In the estimation method of this embodiment, the estimation process is performed using both a plurality of first wavefront information and a plurality of second wavefront information, and it is preferable that, in the plurality of first wavefront information, the incident angle of the first illumination light with respect to the object differs for each piece of first wavefront information, and, in the plurality of second wavefront information, the incident angle of the second illumination light with respect to the object differs for each piece of second wavefront information.

[0419] In the estimation method of this embodiment, the estimation process includes a first optimization process using the first wavefront information as a constraint condition and a second optimization process using the second wavefront information as a constraint condition. Each of the first optimization process and the second optimization process is executed two or more times. The second optimization process is executed continuously on the three-dimensional optical characteristics updated by the continuous execution of the first optimization process.

[0420] In the estimation method of the present embodiment, the estimation process executes a second optimization process on the three-dimensional optical characteristics updated by executing the first optimization process.

[0421] In the estimation method of this embodiment, the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition. A combined process consisting of the first optimization process and the second optimization process is executed two or more times. In the combined process, the first optimization process is executed first. In the combined process, after the second optimization process is executed, the first optimization process is not executed.

[0422] In the estimation method of this embodiment, the composite process executes a first optimization process on the initial values ​​set for the three-dimensional optical characteristics.

[0423] In the estimation method of the present embodiment, control is performed so that the number of times the first optimization process is executed is equal to or greater than the number of times the second optimization process is executed.

[0424] In the estimation method of the present embodiment, control continues during successive composite processes.

[0425] In the estimation method of the present embodiment, after the composite process has been executed a predetermined number of times, control is performed in the composite process to reduce the difference between the number of times the second optimization process has been executed and the number of times the first optimization process has been executed.

[0426] In the estimation method of this embodiment, the first illumination light is light in the infrared region, and the second illumination light is light in the visible region.

[0427] In the estimation method of the present embodiment, the first illumination light is light in the infrared region and satisfies the following conditional formula (A). 2×λ2<λ1 (A) Where: λ1 is the wavelength of the first illumination light, λ2 is the wavelength of the second illumination light, It is.

[0428] The recording medium of the present embodiment is a computer-readable recording medium having a program recorded therein. The recording medium has a program recorded therein for causing a computer having a memory and a processor to execute an estimation process. The memory stores first wavefront information and second wavefront information. The first wavefront information is information of a wavefront acquired based on a first illumination light that has passed through an object, and the second wavefront information is information of a wavefront acquired based on a second illumination light that has passed through the object. The wavelength of maximum intensity in the second illumination light is located on the shorter wavelength side than the wavelength of maximum intensity in the first illumination light. The three-dimensional optical characteristic is a refractive index distribution or an absorptivity distribution. The computer causes the processor to read the first wavefront information and the second wavefront information from the memory, and to execute an estimation process using both the first wavefront information and the second wavefront information.

[0429] In the recording medium of the present embodiment, it is preferable that a memory stores a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information, and a processor executes an estimation process using both the plurality of pieces of first wavefront information and the plurality of pieces of second wavefront information. In the plurality of pieces of first wavefront information, the incident angle of the first illumination light with respect to the object is different for each piece of first wavefront information, and in the plurality of pieces of second wavefront information, the incident angle of the second illumination light with respect to the object is different for each piece of second wavefront information. [Industrial Applicability]

[0430] INDUSTRIAL APPLICABILITY As described above, the present invention is suitable for an estimation device, an estimation system, an estimation method, and a recording medium that can acquire three-dimensional optical characteristics of an object with high accuracy and high spatial resolution even when the object has a large thickness. [Explanation of symbols]

[0431] 1 Estimation device 2. Memory 3 Processors 10, 20 objects 21 Measurement optical system 22 Lens 23 CCD 24 Estimated object 30 Estimation System 31 Light source unit 32 1st light source 33 Second light source 34 Photodetector 35 Stages 36 Dichroic Mirror 37, 40 Beam splitter 38, 39 Mirror 41, 60, 70 Angle change mechanism 42, 61, 71 Drive unit 43, 62, 72 Rotating members 50 Estimation System 51 Illumination optical system 52 Detection optical system 53 Mirror 80 1st light shielding plate 81 2nd light shielding plate 82 First Optical Filter 83 Second Optical Filter 90, 100, 110, 120 Estimation System 91, 101 First photodetector 92, 102 Second photodetector 103 First optical element 104 Second optical element 111 Mirror 112 Beam splitter 113 Optical path length adjustment section 121 Light source 122, 123 Lenses 124 Photodetector 130 Estimation System 131 1st light source 132 Second light source 133 Illumination optical system 133a, 135a Lenses 134 Opening material 134a, 134c Light shielding part 134b Transparent part 135 Imaging Optical System 136 Photodetector 137 Driving Mechanism 138 Dichroic Mirror AX optical axis Lλ1 First illumination light Lλ2 Second illumination light L mea1 First measuring beam L mea2 Second measuring beam L ref1 1st reference light L ref2 2nd reference light OP mea Measurement optical path OP ref Reference optical path RX axis S object

Claims

1. A memory and a processor, the memory stores first wavefront information and second wavefront information; the first wavefront information is information of a wavefront acquired based on a first illumination light having passed through an object, the second wavefront information is information of a wavefront acquired based on a second illumination light having passed through the object, a wavelength of the second illumination light having a maximum intensity is located on a shorter wavelength side than a wavelength of the first illumination light having a maximum intensity, The processor performs an estimation process to estimate three-dimensional optical properties of the object; the three-dimensional optical characteristic is a refractive index distribution or an absorptance distribution, The estimation process uses both the first wavefront information and the second wavefront information, The estimation process includes a first optimization process using the first wavefront information as a constraint condition. A second optimization process using the second wavefront information as a constraint condition, The processor executes the first optimization process a plurality of times; The estimation device, wherein the processor executes the second optimization process a plurality of times.

2. the memory stores a plurality of pieces of first wavefront information and a plurality of pieces of second wavefront information; In the plurality of pieces of first wavefront information, an incident angle of the first illumination light with respect to the object is different for each piece of first wavefront information, In the plurality of pieces of second wavefront information, an incident angle of the second illumination light with respect to the object is different for each piece of second wavefront information, The estimation device according to claim 1 , wherein the estimation process uses both the plurality of first wavefront information and the plurality of second wavefront information.

3. The estimation device described in Claim 1, characterized in that the processor continuously executes the second optimization process on the three-dimensional optical characteristics updated by continuous execution of the first optimization process.

4. The estimation device according to claim 3 , wherein the processor continuously executes the first optimization process for initial values ​​set for the three-dimensional optical characteristics.

5. The processor executes a composite process consisting of the first optimization process and the second optimization process at least twice, In the composite process, the first optimization process is executed first; 2. The estimation device according to claim 1, wherein in the combined process, after the second optimization process is performed, the first optimization process is not performed.

6. The estimation device according to claim 5 , wherein the processor executes the composite processing on initial values ​​set for the three-dimensional optical characteristics.

7. 6. The estimation device according to claim 5, wherein the composite process is controlled so that the number of times the first optimization process is executed is equal to or greater than the number of times the second optimization process is executed.

8. 8. The apparatus according to claim 7, wherein the control continues in successive composite processes.

9. 9. The estimation device according to claim 8, characterized in that, after the composite process has been executed a predetermined number of times, the composite process is controlled to reduce a difference between the number of times the second optimization process is executed and the number of times the first optimization process is executed.

10. the first illumination light is light in the infrared region, The estimation device according to claim 1 , wherein the second illumination light is light in the visible region.

11. the first illumination light is light in the infrared region, 2. The estimation device according to claim 1, wherein the following conditional expression (A) is satisfied: 2 × λ2 < λ1 (A) Where: λ1 is the wavelength of the first illumination light, λ2 is the wavelength of the second illumination light, It is.

12. An estimation device according to any one of claims 1 to 11; a light source unit that emits the first illumination light and the second illumination light; A photodetector; a stage on which the object is placed; An angle changing mechanism, the stage is disposed on an optical path between the light source unit and the photodetector; The estimation system, wherein the angle changing mechanism changes an angle of incidence of the first illumination light with respect to the object and an angle of incidence of the second illumination light with respect to the object.

13. The angle changing mechanism includes a drive device and a rotating member. The rotating member holds the stage, The estimation system according to claim 12 , wherein a rotation axis of the rotating member intersects the object and is perpendicular to an optical axis of the optical path.

14. The angle changing mechanism includes a drive device and a rotating member. the rotating member has a reflective surface; 13. The estimation system according to claim 12, wherein the orientation of the reflecting surface is changed by changing the arrangement angle of the rotating member.

15. An estimation device according to any one of claims 1 to 11, a light source unit that emits the first illumination light and the second illumination light; a stage on which the object is placed; a photodetector and a photodetector separate from the photodetector, the stage is disposed on an optical path between the light source unit and the photodetector; The estimation system is characterized in that the stage is disposed on an optical path between the light source unit and the separate photodetector.

16. The photodetector has a sensitivity to a wavelength band of the first illumination light that is equal to or greater than a first threshold value, and does not have a sensitivity to a wavelength band of the second illumination light that is equal to or greater than the first threshold value; The estimation system according to claim 15, characterized in that the other photodetector has a sensitivity equal to or greater than a second threshold value for the wavelength band of the second illumination light, and does not have a sensitivity equal to or greater than the second threshold value for the wavelength band of the first illumination light.

17. A first optical element for use with the photodetector; a second optical element for use with the other photodetector; the first optical element has a property of transmitting the first illumination light and blocking the second illumination light, The estimation system according to claim 15 , wherein the second optical element has a property of transmitting the second illumination light and blocking the first illumination light.

18. An imaging optical system for forming an optical image of the object; a drive mechanism for changing a distance between a focal position of the imaging optical system and a position of the object in an optical axis direction of the imaging optical system, 18. The estimation system according to claim 15, wherein the illumination by the first illumination light and the illumination by the second illumination light form a partially coherent illumination on the object.

19. An estimation device according to any one of claims 1 to 11, a light source unit that emits the first illumination light and the second illumination light, The light source unit is composed of a plurality of independent light sources having different irradiation angles, An estimation system characterized in that the processor of the estimation device or a processor different from the processor controls whether or not to cause the light source to emit illumination light, thereby changing the angle of incidence of the first illumination light to the object and the angle of incidence of the second illumination light to the object.

20. An estimation device according to any one of claims 1 to 11, a light source unit that emits the first illumination light and the second illumination light; an imaging optical system for forming an optical image of the object; a photodetector for acquiring an image of the object from an optical image of the object; a drive mechanism for changing a distance between a focal position of the imaging optical system and a position of the object in an optical axis direction of the imaging optical system, The estimation system, wherein the illumination by the first illumination light and the illumination by the second illumination light form partially coherent illumination with respect to the object.

21. A method for estimating three-dimensional optical properties of an object, comprising: the three-dimensional optical characteristic is a refractive index distribution or an absorptance distribution, the first wavefront information is information of a wavefront acquired based on a first illumination light that has passed through the object; the second wavefront information is information of a wavefront acquired based on a second illumination light that has passed through the object; a wavelength of the second illumination light having a maximum intensity is located on a shorter wavelength side than a wavelength of the first illumination light having a maximum intensity, performing an estimation process using both the first wavefront information and the second wavefront information; the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition, Executing the first optimization process a plurality of times; The estimation method comprises executing the second optimization process a plurality of times.

22. A computer-readable recording medium having a program recorded thereon for causing a computer having a memory and a processor to execute an estimation process, the first wavefront information is information of a wavefront acquired based on the first illumination light having passed through the object; the second wavefront information is information of a wavefront acquired based on a second illumination light that has passed through the object; a wavelength of the second illumination light having a maximum intensity is located on a shorter wavelength side than a wavelength of the first illumination light having a maximum intensity, The estimation process includes estimating three-dimensional optical properties of the object; the three-dimensional optical characteristic is a refractive index distribution or an absorptance distribution, causing the processor to read the first wavefront information and the second wavefront information from the memory; performing the estimation process using both the first wavefront information and the second wavefront information; the estimation process includes a first optimization process using the first wavefront information as a constraint condition, and a second optimization process using the second wavefront information as a constraint condition, causing the processor to execute the first optimization process a plurality of times; A computer-readable recording medium having recorded thereon a program for causing the processor to execute the second optimization process a plurality of times.

Images