Wavefront measuring device, wavefront measuring method, and method for manufacturing optical system and optical element

Abstract

To provide a wavefront measurement device which has appropriate resolution while suppressing the size of a light reception part.SOLUTION: A wavefront measurement device (1) includes: deflection parts (80, 81) for deflecting light which has been emitted from a light source (10) and has passed through a specimen (30) so as to change a luminous flux width in a first direction of the light; light reception parts (90, 91) for receiving the light from the deflection parts; and a calculation part (100) for calculating a wavefront of the light before entering the deflection parts by using output of the light reception parts and functions normalized relative to each of the first direction and a second direction different from the first direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wavefront measuring device that measures a transmitted wavefront of an optical system. [Background technology]

[0002] Patent Document 1 discloses a wavefront measuring device that irradiates a test optical system with light beams at multiple angles of view, guides the light beams at multiple angles of view emitted from the test optical system to a single light receiving unit (wavefront sensor) via a folding plane mirror and a wedge prism, and measures the wavefronts at multiple angles of view of the test optical system. Patent Document 2 discloses a refractive index distribution measuring device that immerses a test object in two media with different refractive indices, measures the transmitted wavefront, and calculates the refractive index distribution by removing the shape component of the test object from the two transmitted wavefronts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6125131 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-106975 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the wavefront measurement device disclosed in Patent Document 1, the off-axis light beam from the test object has a narrow beam width in the meridional direction due to vignetting, resulting in a small number of data points in the meridional direction of the light beam received by the light-receiving unit (low resolution). A decrease in resolution also degrades the wavefront measurement accuracy. While it is possible to improve resolution by expanding the beam width in the meridional direction by deflecting the light using a prism, the shape of the light beam received by the light-receiving unit is different from the light beam immediately after passing through the test object, and therefore the desired wavefront cannot be obtained by analyzing it as is.

[0005] The refractive index distribution measuring device disclosed in Patent Document 2 requires a light receiving unit with a light receiving surface that is approximately the same as or larger than the diameter of the object to be measured.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a wavefront measuring device, a wavefront measuring method, a method for manufacturing an optical system, and a method for manufacturing an optical element that have an appropriate resolution while suppressing the size of the light receiving portion. [Means for solving the problem]

[0007] A wavefront measuring device according to one aspect of the present invention includes: a first light beam that is incident through a test object; Ru bias a light receiving unit that receives the second light deflected by the deflection unit; and a calculation unit that calculates the wavefront of the first light before it is incident on the deflection unit based on an output of the light receiving unit. the polarization unit polarizes the first light to make the beam width of the second light in a first direction closer to the beam width of the first light in a second direction that is perpendicular to the first direction. .

[0008] Other objects and features of the present invention are illustrated in the following examples. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a wavefront measuring device, a wavefront measuring method, a manufacturing method for an optical system, and a manufacturing method for an optical element that have an appropriate resolution while suppressing the size of the light receiving portion. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a wavefront measuring device according to a first embodiment. [Figure 2] 4 is a flowchart showing a procedure for measuring the wavefront of a test object in the first embodiment. [Figure 3] 5A and 5B are diagrams illustrating signals when a light beam is received by a wavefront sensor before and after deflection by a deflection element in the first embodiment. [Figure 4] FIG. 10 is a schematic configuration diagram of a wavefront measuring device according to a second embodiment. [Figure 5] FIG. 10 is a schematic configuration diagram of a wavefront measuring device according to a third embodiment. [Figure 6]FIG. 10 is a schematic configuration diagram of a wavefront measuring device according to a fourth embodiment. [Figure 7] 10A and 10B are diagrams illustrating signals when a light beam is received by different wavefront sensors before and after deflection by a deflection element in the fourth embodiment. [Figure 8] 1A to 1C are manufacturing process diagrams of a manufacturing method for an optical system. [Figure 9] 1A to 1C are manufacturing process diagrams of a manufacturing method for an optical element. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0012] First, a wavefront measuring device according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the configuration of the wavefront measuring device according to this embodiment.

[0013] The wavefront measuring device 1 is configured to include a light source 10, fibers 20, 21, deflection elements (transmission type diffraction elements, diffraction gratings) 80, 81 as deflection units, wavefront sensors (Shack-Hartmann sensors) 90, 91 as light receiving units, and a computer (calculation unit) 100. The object 30 to be measured is an optical system configured by combining multiple lenses. The wavefront measuring device 1 measures the off-axis transmitted wavefront of the object 30 to be measured.

[0014] The light source 10 is, for example, a semiconductor laser or an LED. Divergent light 200a and 201a emitted from the light source 10 via fibers 20 and 21, respectively, pass through the off-axis of the test object 30 to become test light 200b and 201b. Since the test light 200b and 201b are vignetted when passing through the test object 30, the width of the light beam in the meridional direction is smaller than the width in the sagittal direction.

[0015] The test lights 200b and 201b are diffracted by the deflection elements 80 and 81, respectively, to become test lights 200c and 201c, which are received by the wavefront sensors 90 and 91. The deflection elements 80 and 81 in this embodiment are, for example, amplitude diffraction gratings, phase diffraction gratings, or CGHs (Computer Generated Holograms). Due to the effect of being deflected by the deflection elements 80 and 81, the test lights 200c and 201c are expanded or contracted in the meridional direction (a predetermined direction, the Y direction in FIG. 1 in this embodiment) (expanded in the predetermined direction in this embodiment) before entering the wavefront sensors 90 and 91.

[0016] Signals corresponding to the test lights 200c and 201c received by the wavefront sensors 90 and 91 are sent to the computer 100. The computer 100 calculates the wavefronts of the test lights 200b and 201b of the test object 30 (the wavefronts before the light beams are expanded or contracted by the deflection elements 80 and 81) based on the signals corresponding to the test lights 200c and 201c.

[0017] In this embodiment, the wavefront is calculated using the Shack-Hartmann principle. Specifically, the wavefront sensors 90 and 91 are Shack-Hartmann sensors equipped with a microlens array. When parallel light without wavefront aberration is incident on the Shack-Hartmann sensor, a spot array image with the same period as the period of the microlens array is captured. On the other hand, when light with wavefront aberration is incident on the Shack-Hartmann sensor, the position of each spot in the spot array image shifts in proportion to the inclination of the wavefront of the light incident on each microlens. The wavefront is calculated based on the amount of shift in the spot position.

[0018] Next, a procedure for measuring the wavefront of the test object 30 (wavefront measuring method) in this embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the procedure for measuring the wavefront of the test object 30.

[0019] First, in step S10, the test object 30 is placed, and light is irradiated from the light source 10 onto the test object 30. Subsequently, in step S20, the transmitted light beams 200c and 201c (light beams whose beam widths have changed in the predetermined direction) of the test object 30 expanded and contracted in a predetermined direction (meridional direction) by the deflection elements 80 and 81 are received by the wavefront sensors 90 and 91, respectively.

[0020] FIG. 3 illustrates the expansion and contraction of a light beam by a deflection element. FIG. 3A illustrates an example of a spot array image received by a wavefront sensor in a wavefront measurement optical system in which a wavefront sensor is placed immediately after transmission through the test object 30 (placed so that the wavefront sensor surface is perpendicular to the light propagation direction). Due to vignetting, the number of spots in the meridional (M) direction is smaller than the number of spots in the sagittal (S) direction. FIG. 3B illustrates an example of a spot array image received by a wavefront sensor in a case in which the wavefront sensor is placed after diffraction by a deflection element (the arrangement of this embodiment). The light beam transmitted through the test object 30 is stretched in the meridional (M) direction by deflection, increasing the number of spots and making it approximately the same as the number of spots in the sagittal (S) direction. In other words, the arrangement of this embodiment can improve the resolution in the meridional direction.

[0021] However, the transmitted wavefront of the test object 30 to be actually measured is the wavefront before the test light is expanded or contracted by the deflection element. Therefore, in step S30 of FIG. 2, the computer 100 calculates the transmitted wavefront of the test object before the test light is expanded or contracted by the deflection element. Specifically, the computer 100 calculates the transmitted wavefront of the test object before the test light is expanded or contracted by the deflection element using the signal of FIG. 3B (the signal of the test light received by the wavefront sensor) and normalized functions with respect to a predetermined direction and a direction perpendicular to the predetermined direction. In this embodiment, the predetermined direction (first direction) is the meridional direction (Y direction in FIG. 1), and the direction perpendicular to the predetermined direction (a second direction different from the first direction) is the sagittal direction (X direction in FIG. 1), but is not limited thereto. Step S30 can be further divided into three steps, SA1, SA2, and SA3, which are shown as step A in FIG. 2.

[0022] First, in step SA1, the computer 100 calculates the tilt of the wavefront at each microlens and the coordinates of each microlens for the light beam received by the wavefront sensors 90 and 91. Here, the wavefront of the light beam incident on the wavefront sensors 90 and 91 is W(X,Y), and the coordinates of the microlens located in the i-th row and j-th column of the microlens array are (X ij ,Y ij ), and the coordinates of the center of gravity of the focused spot formed by the lens are (X ij +δX ij ,Y ij +δY ij ) In this case, the tilt of the wavefront at each microlens array is expressed by the following equation (1), where f is the distance between the microlens array in the wavefront sensor and the image sensor (CMOS sensor or CCD sensor).

[0023]

number

[0024] If the arrangement direction of the microlenses and the arrangement direction of the pixels of the image sensor are approximately the same, the coordinates of each microlens (X ij ,Y ij ) is expressed by the following equation (2). That is, at this time, the coordinates (X ij ,Y ij ) are values arranged in the X and Y directions at the period of the microlens array (for example, Λ = 150 μm). Here, Xc and Yc are the barycentric coordinates of the light beam. The barycentric coordinates are calculated by dividing the intensity of the light incident on each microlens by I ij When the center of gravity is calculated, the light intensity I is expressed by the following formula (3). ij If the value is above a certain threshold, all I ij =1 can also be used.

[0025]

number

[0026]

number

[0027] Next, in step SA2, the computer 100 calculates the coordinates (X ij ,Y ij ) is normalized. The normalization is performed in a predetermined direction (meridional direction, Y direction in FIG. 1) and in a direction perpendicular to the predetermined direction (sagittal direction, X direction in FIG. 1) as expressed by the following equation (4). However, (x ij ,y ij ) are the normalized coordinates of each microlens, and max(argument) is a function that returns the maximum value of the argument.

[0028]

number

[0029] Finally, in step SA3, the computer 100 fits the inclination of the wavefront at each microlens using a function normalized with respect to each of the predetermined direction and the direction perpendicular to the predetermined direction. This makes it possible to calculate the wavefront of the test light before it is expanded or contracted by the deflection element. As a function normalized with respect to each of the predetermined direction and the direction perpendicular to the predetermined direction, for example, a Zernike function Z normalized with respect to each of the X and Y directions can be used. L It is possible to use a differential Zernike function obtained by partially differentiating (r, θ) with respect to X and Y. When the coordinate system before normalization is (X, Y) and the polar coordinate in the normalized coordinate system (x, y) is (r, θ), the normalized differential Zernike function is expressed as in the following formula (5) using an integer N (N≧0) and an integer M (|M|≦N).

[0030]

number

[0031] When the wavefront tilt of each microlens array is fitted using a function normalized with respect to a predetermined direction and a direction perpendicular to the predetermined direction, the same fitting coefficients are obtained mathematically regardless of whether the light beam is stretched or contracted by the deflection element. In other words, the fitting coefficients (transmitted wavefront) calculated in step SA3 are equal to the fitting coefficients (transmitted wavefront) before the light beam is stretched or contracted by the deflection element. However, in practice, the accuracy of the fitting coefficients varies depending on the resolution of the data acquired by the wavefront sensor. In this embodiment, the transmitted wavefront of the test object can be measured with high accuracy by using the flow shown in Figure 2.

[0032] In step SA3, the wavefront tilt is fitted with a normalized differential Zernike function, but this embodiment is not limited to this. Alternatively, the wavefront may be obtained by integrating the wavefront tilt and then fitting with a normalized Zernike function. The function used for normalization is not limited to a Zernike function or a differential Zernike function, and a two-dimensional trigonometric function or a Legendre polynomial may also be used. Furthermore, a new function may be created using Schmidt orthogonalization or the like.

[0033] Adding a calculation step for the backward propagation of light to the flow of Fig. 2 can further improve the accuracy of wavefront calculation. When the light beam is deflected using deflection elements 80 and 81 as in this embodiment, an optical path length distribution occurs within the light beam in a predetermined direction. For example, within light beam 200c of Fig. 1, the light beam at the -Y position has a longer propagation distance than the light beam at the +Y position. Therefore, the optical path length distribution caused by the difference in propagation distance can be eliminated by using the backward propagation of light.

[0034] Furthermore, to suppress deformation of the wavefront due to propagation from the pupil of the test object 30 to the wavefront sensors 90 and 91, backpropagation may be performed from the wavefront sensors 90 and 91 to the pupil of the test object 30. Backpropagation may be ray tracing or propagation using an angular spectrum method. For example, when ray tracing is used, ray tracing may be performed in step SA1 based on the tilt and coordinates of the wavefront at each microlens, and steps SA2 and SA3 may be performed after replacing the coordinates of each microlens with the coordinates after ray tracing. When the angular spectrum method is used, backpropagation may be performed after calculating the wavefront in step SA3.

[0035] Instead of backpropagating the light from the wavefront sensors 90 and 91 to the pupil of the test object 30, it is also possible to insert lenses between the test object 30 and the wavefront sensors 90 and 91, respectively, to establish a conjugate relationship between the pupil of the test object 30 and the wavefront sensors 90 and 91. If the inserted lenses also function as beam expanders, the size of the light beams incident on the wavefront sensors 90 and 91 can be adjusted to a more appropriate size.

[0036] As described above, in this embodiment, the wavefront measuring device 1 includes a deflection unit (deflection elements 80, 81), a light receiving unit (wavefront sensors 90, 91), and a calculation unit (computer 100). The deflection unit deflects light emitted from the light source 10 and transmitted through the test object 30 (light transmitted through or reflected by the test object 30), and changes (expands or contracts) the beam width of the light in a first direction (a predetermined direction). The light receiving unit receives the light from the deflection unit. The calculation unit calculates the wavefront of the light before it enters the deflection unit (light before the beam width is changed) using the output of the light receiving unit and normalized functions for the first direction and a second direction different from the first direction.

[0037] In this embodiment, the beam width of the light before entering the deflection unit is smaller in the first direction than in the second direction, and the deflection unit expands the beam width of the light in the first direction. However, this embodiment is not limited to this. For example, if the beam width in the first direction is larger than the beam width in the second direction, the deflection unit can reduce the beam width of the light in the first direction.

[0038] In this embodiment, a transmissive diffraction grating is used as the deflection element, but a reflective diffraction grating may also be used. In either case, the expansion / contraction ratio of the light beam can be adjusted by the grating period or the diffraction order. Furthermore, a prism or Fresnel prism may be used instead of a diffraction grating. When a prism is used, the expansion / contraction ratio of the light beam can be adjusted by changing the apex angle, refractive index, or angle of incidence of the prism. Furthermore, when a prism is used, the optical path length distribution in a predetermined direction within the light beam that occurs when a diffraction grating is used does not occur.

[0039] In this embodiment, the wavefront sensors 90 and 91 are Shack-Hartmann sensors equipped with microlens arrays, but this is not limiting. Alternatively, the wavefront sensors 90 and 91 may be shearing interferometers (Talbot interferometers) equipped with a Hartmann mask. The Hartmann mask may be either a two-dimensional phase grating or a two-dimensional absorption grating. In a shearing interferometer, the wavefront can be calculated by the Fourier transform method from the distortion of the self-image formed behind the Hartmann mask. Alternatively, a pinhole array (an array in which pinholes are spaced far enough apart that interference between light transmitted through one pinhole and light transmitted through an adjacent pinhole is negligible) can be used as the Hartmann mask to recover the wavefront using the same principle as a Shack-Hartmann sensor.

[0040] Alternatively, a method of calculating a wavefront using intensity information of the test light may be used. This method is as follows: Image sensors (not including a microlens array or a Hartmann mask) fixed on a linear stage are arranged as wavefront sensors 90 and 91. A plurality of images are captured while the linear stage is driven. A computer 100 calculates the transmitted wavefront of the test object 30 based on the captured images. The method of calculating the wavefront from the image may be a method using the transport of intensity equation or a method of performing optimization calculations based on the initial value of a specific wavefront. Alternatively, the wavefront may be calculated using artificial intelligence (AI) that has undergone machine learning to learn the relationship between the wavefront and the image.

[0041] 3, the beam width in the sagittal direction of the test light beam is approximately the same as the screen size of the wavefront sensor (a size that provides high resolution), and the beam width in the meridional direction is smaller than the screen size of the wavefront sensor (a size that provides only low resolution). Therefore, the beam width in the meridional direction is expanded by deflection elements 80 and 81. If the beam width in the meridional direction is approximately the same as the screen size of the wavefront sensor and the beam width in the sagittal direction is larger than the screen size of the wavefront sensor, the sagittal direction should be set as the predetermined direction, and the deflection elements 80 and 81 and wavefront sensors 90 and 91 should be arranged so as to reduce the beam in that direction.

[0042] According to this embodiment, it is possible to provide a wavefront measuring device that has an appropriate resolution while suppressing the size of the wavefront sensor. [Example]

[0043] Next, a wavefront measuring device according to a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a schematic diagram of the configuration of the wavefront measuring device 2 according to this embodiment.

[0044] The wavefront measuring device 2 has a light source 11, a pinhole 25, a mirror 40 with a two-axis rotation stage, lenses 50 and 51, a beam splitter 60, and a three-axis linear stage 125. The wavefront measuring device 2 also has a deflection element (Fresnel prism) 82, a wavefront sensor 92, a two-axis linear and two-axis rotation stage 95, and a computer 100. The deflection element 82 and the wavefront sensor 92 are arranged on the two-axis linear and two-axis rotation stage 95. The wavefront sensor 92 is a Talbot interferometer with a Hartmann mask.

[0045] Light 200a emitted from the light source 11 (e.g., a DPSS laser) through the pinhole 25 is collimated by the lens 50, reflected by the beam splitter 60, and transmitted through the lens 51 to be focused on a plane corresponding to the image plane position of the test object 30. The test light 200a then diverges and enters the test object 30. After transmitting through the test object 30, the test light 200a is reflected by the two-axis rotation stage-equipped mirror 40. Test light 200b, which transmits through the test object 30 again, passes through the lens 51 and the beam splitter 60 and is deflected by the deflection element 82. The beam 200c deflected by the deflection element 82 is received by the wavefront sensor 92 in a state where it is expanded or contracted in a predetermined direction. The beam expansion or contraction by the deflection element 82 allows appropriate resolution to be obtained. A signal of the test light 200c received by the wavefront sensor 92 is sent to the computer 100. The computer 100 calculates the transmitted wavefront of the test object before the test light is expanded or contracted by the deflection element, using a function normalized with respect to each of a predetermined direction and a direction perpendicular to the predetermined direction.

[0046] The three-axis rectilinear stage 125 can be driven in the X, Y, and Z directions in FIG. 4. The two-axis rotary stage mirror 40 can rotate about the X and Y axes. The two-axis rectilinear / two-axis rotary stage 95 can be driven linearly in the X and Y directions and rotate about the X and Y axes. By driving the three-axis rectilinear stage 125 and the two-axis rotary stage mirror 40, the wavefront measuring device 2 can measure the wavefront of transmitted light corresponding to multiple angles of view of the test object 30. In addition, the two-axis rectilinear / two-axis rotary stage 95 adjusts the position and size of the light beam incident on the wavefront sensor 92, thereby achieving wavefront measurement with an appropriate resolution. [Example]

[0047] Next, a wavefront measuring device according to a third embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a schematic diagram of the configuration of the wavefront measuring device 3 according to this embodiment.

[0048] The wavefront measuring device 3 includes a light source 12, a fiber 20, lenses 50, 51, and 52, a half mirror 65, a transmission flat (TF) 70, a CGH 75, a deflection element (reflective diffraction grating) 83, a wavefront sensor 94, and a computer 100. The wavefront measuring device 3 is a Fizeau interferometer. The wavefront sensor 94 is an image sensor (a CMOS sensor or a CCD sensor). The test object 35 in this embodiment is a toric lens (optical element) used as an fθ lens. The wavefront measuring device 3 measures the wavefront of light reflected from the toric surface to examine the surface shape of the test object 35. Figure 5 shows the optical path for the sub-scanning cross section of the test object 35 (the main scanning direction is the X direction in Figure 5).

[0049] Light 200a emitted from the light source 12 (e.g., a HeNe laser) via the fiber 20 is converted into parallel light by the lens 50, passes through the half mirror 65, and is partially transmitted and partially reflected by the transmission flat surface 70. The light reflected by the transmission flat surface 70 becomes reference light 200R in the Fizeau interferometer. The transmission flat surface 70 is disposed on a piezo stage (not shown) so that it can be driven. The test light 200a transmitted through the transmission flat surface 70 passes through the CGH to become convergent light having different curvatures in the X and Y directions, and is incident on the surface of the test object 35 approximately perpendicularly. The test light 200b reflected by the surface of the test object 35 passes through the CGH and the transmission flat surface 70 again, and interferes with the reference light 200R. The interference light (200b, 200R) is reflected by the half mirror 65, passes through lenses 51 and 52, and is incident on the deflection element 83. The interference light (200c, 200Rc) deflected by the deflection element 83 is expanded or contracted in a predetermined direction and received by the image sensor 94. The signal of the interference light (200c, 200Rc) received by the image sensor 94 is sent to the computer 100. The computer 100 calculates the reflected wavefront of the test object before the light beam is expanded or contracted by the deflection element using a function normalized with respect to each of the predetermined direction and a direction perpendicular to the predetermined direction. The wavefront calculation may be performed by a fringe scan method or a Fourier transform method using carrier fringes.

[0050] The diameter of a toric lens in the main scanning direction (X direction in FIG. 5) is larger than the diameter in the sub-scanning direction (Y direction in FIG. 5). Therefore, if the reflected light from the toric surface is received directly by an image sensor, the resolution in the sub-scanning direction will be lower than the resolution in the main scanning direction. On the other hand, according to this embodiment, the beam width in the sub-scanning direction is expanded by deflection using deflection element 83, thereby achieving wavefront measurement with appropriate resolution. [Example]

[0051] Next, a wavefront measuring device according to a fourth embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of the configuration of the wavefront measuring device 4 according to this embodiment.

[0052] The wavefront measuring device 4 includes a light source 10, a fiber 20, lenses 50 and 51, a deflection element (prism) 84, a wavefront sensor 90, and a computer 100. The object 36 to be measured in this embodiment is a molded lens (optical element).

[0053] Light 200a emitted from the light source 10 through the fiber 20 becomes convergent light via lenses 50 and 51 and enters the test object 36. Test light 200b transmitted through the test object 36 is deflected by the deflection element 84, and the light beam in a predetermined direction is expanded or contracted, and is received by the wavefront sensor 90. A signal of test light 200c received by the wavefront sensor 90 is sent to the computer 100. The computer 100 calculates the wavefront of the test light 200b before the light beam is expanded or contracted by the deflection element 84, using functions normalized with respect to each of the predetermined direction and a direction perpendicular to the predetermined direction.

[0054] Generally, when the test object 36 is a single lens, the wavefront transmitted through the test object 36 has large wavefront aberration, unlike the transmitted wavefront of an optical system composed of multiple lenses. When the wavefront aberration is large, it is preferable to insert as few lenses as possible between the test object 36 and the wavefront sensor 90. This is to avoid the occurrence of unexpected aberrations due to inserted lenses (aberrations caused by variations in the optical path of light rays). In this case, the wavefront sensor 90 needs to have a screen size approximately the same as the diameter of the test object.

[0055] FIG. 7 shows an example of a signal obtained by the wavefront sensor 90 in this embodiment. Generally, the screen size (size of the light-receiving surface) of the wavefront sensor 90 is smaller in the vertical direction than in the horizontal direction. Therefore, a wavefront sensor 90 having a screen size similar to the diameter of the test object 36 means a sensor with a size that allows a light beam to enter the wavefront sensor 90 in the vertical direction, as shown in FIG. 7(A). Generally, the larger the screen size of the wavefront sensor 90, the more expensive it becomes, so it is preferable to select a wavefront sensor with as small a screen as possible, provided that appropriate resolution is obtained.

[0056] In this embodiment, the deflection element 84 compresses the light beam in a predetermined direction (the vertical direction of the wavefront sensor 90) to achieve wavefront measurement using a wavefront sensor with a small screen, as shown in FIG. 7B . In this embodiment, the deflection element 84 is arranged to reduce the beam width of the test light 200b in the predetermined direction, but this is not limiting. For example, if the test light 200b is smaller than the wavefront sensor 90, the horizontal direction of the wavefront sensor 90 is set as the predetermined direction, and the deflection element 84 and the wavefront sensor 90 are arranged to expand the beam in the predetermined direction. That is, in this embodiment, the width of the light receiving surface (screen) of the light receiving unit (wavefront sensor 90) in the first direction (vertical direction) is smaller than the width in the second direction (horizontal direction), and the deflection unit (deflector element 84) reduces the beam width of the light in the first direction. Alternatively, the width of the light receiving surface (screen) of the light receiving unit in the first direction is larger than the width in the second direction, and the deflection unit expands the beam width of the light in the first direction, thereby making it possible to effectively utilize the light receiving area (light receiving surface) in the lateral direction of the wavefront sensor 90. [Example]

[0057] Next, a method for manufacturing an optical system according to a fifth embodiment of the present invention will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the method for manufacturing an optical system according to this embodiment. For example, the results of wavefront measurement using the wavefront measuring apparatus 1 according to the first embodiment or the wavefront measuring apparatus 2 according to the second embodiment can be fed back to a method for manufacturing an optical system (test object 30).

[0058] First, in step S101, an optical system is assembled using optical elements, and the position of each element is adjusted (optical system assembly and adjustment). Subsequently, in step S102, the optical performance (optical accuracy) of the assembled and adjusted optical system is evaluated. Here, the optical performance of the optical system is evaluated using the results of wavefront measurement using, for example, the wavefront measuring device 1 of Example 1 or the wavefront measuring device 2 of Example 2. If the optical performance is insufficient in step S102, the process returns to step S101, and the optical system is assembled and adjusted again. On the other hand, if the optical performance is satisfactory in step S102, this flow related to the manufacturing method of the optical system is terminated.

[0059] FIG. 9 shows a manufacturing method of an optical element using molding. The optical element is manufactured through an optical element design step (step S201), a mold design step (step S202), and an optical element molding step (step S203) using the designed mold. Here, the optical element is not limited to being molded using a mold (molding), but may also be manufactured by processing such as polishing. Therefore, step S203 may be replaced with a molding step other than the molding step. The shape accuracy of the molded optical element is evaluated (step S204). If the accuracy is insufficient, the mold is corrected and the optical element is molded again. If the shape accuracy is good, the optical performance of the optical element is evaluated (step S205). If the optical performance (optical accuracy) is low, the optical surface is corrected and the optical element is redesigned. On the other hand, if the optical performance is satisfactory in step S205, the process proceeds to mass production of optical elements (step S206). For example, the wavefront measuring device 3 of the third embodiment can be used to evaluate the shape accuracy in step S204. Furthermore, the optical performance evaluation in step S205 can be performed using, for example, the wavefront measuring device 4 of Example 4. The above-described method for manufacturing an optical element can also be applied to the manufacture of optical elements by grinding and polishing, without relying on a mold.

[0060] According to each embodiment, it is possible to provide a wavefront measuring device, a wavefront measuring method, a manufacturing method for an optical system, and a manufacturing method for an optical element that have an appropriate resolution while suppressing the size of the light receiving unit.

[0061] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0062] 1. Wavefront measurement device 80, 81 Deflection element (deflection part) 90, 91 Wavefront sensor (light receiving part) 100 Computer (calculation section)

Claims

1. a deflection unit that deflects the first light that has entered through the object to be measured; a light receiving unit that receives the second light deflected by the deflection unit; a calculation unit that calculates a wavefront of the first light before it is incident on the deflection unit based on an output of the light receiving unit, the deflection unit deflects the first light to bring a beam width of the second light in a first direction closer to a beam width of the first light in a second direction that is perpendicular to the first direction.

2. 2. The wavefront measuring device according to claim 1, wherein the light receiving unit has a microlens array.

3. A deflection unit that deflects a first light incident through a test object to expand a beam width of the first light in a first direction; a light receiving unit that receives the second light deflected by the deflection unit; a calculation unit that calculates a wavefront of the first light before it is incident on the deflection unit based on an output of the light receiving unit, The wavefront measuring device is characterized in that the light receiving unit has a microlens array.

4. 4. The wavefront measuring device according to claim 1, wherein the light receiving section has a Hartmann mask.

5. A deflection unit that deflects a first light incident through a test object to expand a beam width of the first light in a first direction; a light receiving unit that receives the second light deflected by the deflection unit; a calculation unit that calculates a wavefront of the first light before it is incident on the deflection unit based on an output of the light receiving unit, The wavefront measuring device is characterized in that the light receiving unit has a Hartmann mask.

6. 6. The wavefront measuring device according to claim 1, wherein the light receiving unit is an image sensor.

7. 3. The wavefront measuring apparatus according to claim 1, wherein the first beam width is smaller than the second beam width.

8. 8. The wavefront measuring device according to claim 1, wherein the deflecting unit is a diffraction grating.

9. A wavefront measuring device as described in any one of claims 1 to 8, characterized in that the first direction is a meridional direction.

10. deflecting the first light that has entered the deflection unit via the object to be measured; receiving, using a light receiving unit, the second light deflected by the deflection unit; calculating a wavefront of the first light before it is incident on the deflection unit based on an output of the light receiving unit, a step of deflecting the first light, wherein the first light is deflected to bring a beam width of the second light in a first direction closer to a beam width of the first light in a second direction that is perpendicular to the first direction.

11. A method for manufacturing an optical system, comprising: Assembling the optical system as the test object; and evaluating optical performance of the optical system based on the wavefront calculated by the wavefront measurement method according to claim 10.

12. A method for manufacturing an optical element, comprising: a step of molding the optical element as the test object; and evaluating optical performance of the optical element based on the wavefront calculated by the wavefront measurement method according to claim 10.

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