JP2024063078A - Wavefront measurement device, wavefront measurement method, optical system, and manufacturing method of optical element - Google Patents

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

The present invention relates to a wavefront measuring device that measures the transmitted wavefront of an optical system.

Patent Document 1 discloses a wavefront measuring device that irradiates a light beam with multiple angles of view onto an optical system to be tested, guides the light beams with multiple angles of view emitted from the optical system to a single light receiving unit (wavefront sensor) via a folding plane mirror and a wedge prism, and measures the wavefronts of the optical system to be tested at multiple angles of view. 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 components of the test object from the two transmitted wavefronts.

Patent No. 6125131 JP 2011-106975 A

However, in the wavefront measurement device disclosed in Patent Document 1, the off-axis light beam of the test object has a narrow light 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). When the resolution decreases, the measurement accuracy of the wavefront also deteriorates. It is possible to improve the resolution by expanding the light beam width in the meridional direction by deflecting the light beam using a prism, but because 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, the desired wavefront cannot be obtained even if it is analyzed as is.

The refractive index distribution measuring device disclosed in Patent Document 2 requires a light receiving unit with a light receiving surface that is equal to or larger than the diameter of the test object.

The present invention aims 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 appropriate resolution while suppressing the size of the light receiving unit.

A wavefront measuring device according to one aspect of the present invention includes a deflection unit that expands the beam width of the first light in a first direction by deflecting the first light incident through a test object, 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 the output of the light receiving unit.

Other objects and features of the present invention are described in the following examples.

The present invention provides 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 appropriate resolution while suppressing the size of the light receiving unit.

1 is a schematic configuration diagram of a wavefront measuring device in a first embodiment. 5 is a flowchart showing a procedure for measuring a wavefront of a test object in the first embodiment. 5A to 5C 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. FIG. 11 is a schematic configuration diagram of a wavefront measuring device in a second embodiment. FIG. 11 is a schematic configuration diagram of a wavefront measuring device in a third embodiment. FIG. 13 is a schematic configuration diagram of a wavefront measuring device in a fourth embodiment. 13A to 13C are diagrams showing signals when a light beam is received by different wavefront sensors before and after deflection by a deflection element in the fourth embodiment. 3A to 3C are manufacturing process diagrams of a manufacturing method for an optical system. 1A to 1C are manufacturing process diagrams of a manufacturing method for an optical element.

The following describes in detail an embodiment of the present invention with reference to the drawings.

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 wavefront measuring device according to the first embodiment.

The wavefront measuring device 1 is configured with a light source 10, fibers 20, 21, deflection elements (transmissive 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 test object 30 is an optical system configured by combining multiple lenses. The wavefront measuring device 1 measures the off-axis transmitted wavefront of the test object 30.

The light source 10 is, for example, a semiconductor laser or an LED. The divergent light 200a, 201a emitted from the light source 10 through the fibers 20, 21, respectively, passes through the off-axis of the test object 30 to become test light 200b, 201b. The test light 200b, 201b is vignetted when passing through the test object 30, so the width of the light beam in the meridional direction is smaller than the width in the sagittal direction.

The test light beams 200b and 201b are diffracted by the deflection elements 80 and 81 to become test light beams 200c and 201c, respectively, and are received by the wavefront sensors 90 and 91. The deflection elements 80 and 81 in this embodiment are, for example, amplitude type diffraction gratings, phase type diffraction gratings, or CGHs (Computer Generated Holograms). The test light beams 200c and 201c are deflected by the deflection elements 80 and 81, and enter the wavefront sensors 90 and 91 in a state in which they are expanded or contracted in the meridional direction (a specified direction, in this embodiment, the Y direction in FIG. 1) (expanded in the specified direction in this embodiment).

The 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 stretched or contracted by the deflection elements 80 and 81) based on the signals corresponding to the test lights 200c and 201c.

In this embodiment, the wavefront is calculated using the Shack-Hartmann principle. That is, 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.

Next, the procedure for measuring the wavefront of the test object 30 (wavefront measurement 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.

First, in step S10, the test object 30 is placed, and light is irradiated from the light source 10 onto the test object 30. Next, in step S20, the transmitted light 200c, 201c (light whose light beam width has changed in the specified direction) of the test object 30 expanded or contracted in a specified direction (meridional direction) by the deflection elements 80, 81 is received by the wavefront sensors 90, 91, respectively.

Figure 3 is a diagram showing the expansion and contraction of a light beam by a deflection element. Figure 3 (A) is an example of a spot array image received by a wavefront sensor when assuming a wavefront measurement optical system in which a wavefront sensor is placed (placed so that the wavefront sensor surface is perpendicular to the light traveling direction) immediately after transmission through the test object 30. Due to the effect of vignetting, the number of spots in the meridional (M) direction is less than the number of spots in the sagittal (S) direction. Figure 3 (B) is an example of a spot array image received by a wavefront sensor when a wavefront sensor is placed after diffraction by a deflection element (the arrangement of this embodiment). The transmitted light beam of the test object 30 is stretched in the meridional (M) direction by deflection, increasing the number of spots, and becoming approximately the same as the number of spots in the sagittal (S) direction. In other words, by using an arrangement such as that of this embodiment, the resolution in the meridional direction can be increased.

However, the transmitted wavefront of the test object 30 to be actually measured is the wavefront before it is expanded or contracted by the deflection element. Therefore, in step S30 in 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 in FIG. 3B (the signal of the test light received by the wavefront sensor) and a function normalized for each of the predetermined direction and the 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 (second direction different from the first direction) is the sagittal direction (X direction in FIG. 1), but is not limited to these. In more detail, step S30 can be divided into three steps, steps SA1, SA2, and SA3, which are shown as step A in FIG. 2.

First, in step SA1, the computer 100 calculates the inclination 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), the coordinates of the microlens located in the i-th row and j-th column of the microlens array are ( _Xij , _Yij ), and the coordinates of the center of gravity of the focused spot formed by the lens are ( _Xij + _δXij , _Yij + _δYij ). At this time, the inclination of the wavefront at each microlens array is expressed by the following formula (1). Here, f is the distance between the microlens array in the wavefront sensor and the image sensor (CMOS sensor or CCD sensor).

If the arrangement direction of the microlenses and the arrangement direction of the pixels of the image sensor are approximately the same, the coordinates ( _Xij , _Yij ) of each microlens are expressed by the following formula (2). That is, the coordinates ( _Xij , _Yij ) of each microlens at this time are values arranged in the X direction and the Y direction at the period of the microlens array (for example, Λ=150 μm). However, Xc and Yc are the barycentric coordinates of the light beam. The barycentric coordinates are values expressed by the following formula (3) when the intensity of light incident on each microlens is _Iij . The light intensity _Iij used in calculating the barycentric center may all be _Iij =1 if it is a value equal to or greater than a certain threshold value.

Next, in step SA2, the computer 100 normalizes the coordinates (X _ij , Y _ij ) of each microlens. The normalization is performed in a predetermined direction (meridional direction, Y direction in FIG. 1) and a direction perpendicular to the predetermined direction (sagittal direction, X direction in FIG. 1) as expressed by the following formula (4), where (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.

Finally, in step SA3, the computer 100 fits the inclination of the wavefront in each microlens using a function normalized for each of the predetermined direction and the direction perpendicular to the predetermined direction. This allows the wavefront of the test light before it is expanded or contracted by the deflection element to be calculated. As the function normalized for each of the predetermined direction and the direction perpendicular to the predetermined direction, for example, a differential Zernike function obtained by partially differentiating the Zernike function _ZL (r, θ) normalized for each of the XY directions with respect to X and Y can be used. 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 the following formula (5) using an integer N (N≧0) and an integer M (|M|≦N).

When the inclination of the wavefront in each microlens array is fitted using a function normalized for each of a specified direction and a direction perpendicular to the specified direction, the same fitting coefficient is obtained mathematically regardless of whether the light beam is stretched or not by the deflection element. In other words, the fitting coefficient (transmitted wavefront) calculated in step SA3 is equal to the fitting coefficient (transmitted wavefront) before the light beam is stretched or not by the deflection element. In reality, however, the accuracy of the fitting coefficient 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 in Figure 2.

In step SA3, the wavefront slope is fitted with a normalized differential Zernike function, but this embodiment is not limited to this. Alternatively, the wavefront slope may be integrated to obtain a wavefront, and then the normalized Zernike function may be fitted. The function used for normalization is not limited to the Zernike function or the differential Zernike function, and two-dimensional trigonometric functions or Legendre polynomials may be used. A new function may also be created by using Schmidt orthogonalization, etc.

The accuracy of wavefront calculation can be further improved by adding a calculation process for the reverse propagation of light to the flow in Figure 2. When the light beam is deflected using deflection elements 80 and 81 as in this embodiment, an optical path length distribution occurs in a predetermined direction within the light beam. For example, within light beam 200c in Figure 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 differences in propagation distance can be eliminated by using the reverse propagation of light.

In addition, to suppress deformation of the wavefront due to propagation from the pupil of the test object 30 to the wavefront sensors 90 and 91, reverse propagation may be performed from the wavefront sensors 90 and 91 to the pupil of the test object 30. Reverse propagation may be ray tracing or propagation by angular spectrum method. For example, when ray tracing is used, ray tracing is performed from the tilt and coordinates of the wavefront at each microlens in step SA1, and the coordinates of each microlens are replaced with the coordinates after ray tracing, and steps SA2 and SA3 are performed. When the angular spectrum method is used, reverse propagation may be performed after calculating the wavefront in step SA3.

Instead of backpropagating from the wavefront sensors 90 and 91 to the pupil of the test object 30, a lens can be inserted between the test object 30 and the wavefront sensors 90 and 91, respectively, to make the pupil of the test object 30 and the wavefront sensors 90 and 91 in a conjugate relationship. If the inserted lens also functions as a beam expander, the size of the light beam incident on the wavefront sensors 90 and 91 can be adjusted to a more appropriate size.

As described above, in this embodiment, the wavefront measuring device 1 has 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 passing 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 (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 changes) using the output of the light receiving unit and a function normalized for each of the first direction and a second direction different from the first direction.

In this embodiment, the light before entering the deflection unit has a smaller beam width in a first direction than the beam width in a 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.

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. A prism or Fresnel prism may also 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. When a prism is used, the optical path length distribution in a specified direction inside the light beam that occurs when a diffraction grating is used does not occur.

In this embodiment, the wavefront sensors 90 and 91 are Shack-Hartmann sensors equipped with microlens arrays, but are not limited thereto. 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 type diffraction grating or a two-dimensional absorption type diffraction grating. In the 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 the pinholes are so far apart that the interference between the light transmitted through one pinhole and the light transmitted through the adjacent pinholes can be negligible) may be used as the Hartmann mask to recover the wavefront using the same principle as the Shack-Hartmann sensor.

Alternatively, a method of calculating the wavefront using intensity information of the test light may be used. The method is as follows. Image sensors (not including a microlens array or Hartmann mask) fixed on a linear stage are arranged as wavefront sensors 90 and 91. A plurality of images are captured while driving the linear stage. 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 a 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 been machine-learned to learn the relationship between the wavefront and the image.

In this embodiment, as shown in FIG. 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). For this reason, the beam width in the meridional direction is expanded by the 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 is set as the specified direction, and the deflection elements 80 and 81 and the wavefront sensors 90 and 91 are positioned so as to reduce the beam in that direction.

This embodiment provides a wavefront measuring device that has an appropriate resolution while reducing the size of the wavefront sensor.

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 wavefront measuring device 2 according to the present embodiment.

The wavefront measuring device 2 has a light source 11, a pinhole 25, a mirror 40 with a two-axis rotation stage, lenses 50, 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.

The light 200a emitted from the light source 11 (e.g., a DPSS laser) through the pinhole 25 becomes parallel light at the lens 50, is reflected by the beam splitter 60, and passes through the lens 51 to be focused on a surface corresponding to the image plane position of the test object 30. The test light 200a then diverges and enters the test object 30. After passing through the test object 30, the test light 200a is reflected by the mirror 40 with a two-axis rotating stage, and the test light 200b that passes 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 light beam 200c deflected by the deflection element 82 is received by the wavefront sensor 92 in a state of being expanded and contracted in a predetermined direction. The light beam expansion and contraction by the deflection element 82 provides an appropriate resolution. The signal of the test light 200c received by the wavefront sensor 92 is sent to the computer 100. The computer 100 uses a function normalized for each of the predetermined direction and the direction perpendicular to the predetermined direction to calculate the transmitted wavefront of the test object before the test light is stretched or expanded by the deflection element.

The three-axis linear 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 linear/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 linear stage 125 and the two-axis rotary stage mirror 40, the wavefront measuring device 2 realizes wavefront measurement of transmitted light corresponding to multiple angles of view of the test object 30. In addition, the two-axis linear/two-axis rotary stage 95 adjusts the position and size of the light beam incident on the wavefront sensor 92 to realize wavefront measurement with appropriate resolution.

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 wavefront measuring device 3 according to the present embodiment.

The wavefront measuring device 3 includes a light source 12, a fiber 20, lenses 50, 51, 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 (CMOS sensor or 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 the reflected light from the toric surface to check 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).

The light 200a emitted from the light source 12 (e.g., a HeNe laser) through the fiber 20 becomes parallel light at the lens 50, passes through the half mirror 65, and is partially transmitted and partially reflected at the transmission plane 70. The light reflected at the transmission plane 70 becomes the reference light 200R in the Fizeau interferometer. The transmission plane 70 is arranged on a piezo stage (not shown) so that it can be driven. The test light 200a transmitted through the transmission plane 70 passes through the CGH and becomes convergent light with different curvatures in the X and Y directions, and enters the surface of the test object 35 approximately perpendicularly. The test light 200b reflected at the surface of the test object 35 passes through the CGH and the transmission plane 70 again, and interferes with the reference light 200R. The interference light (200b, 200R) is reflected at the half mirror 65, passes through the lenses 51 and 52, and enters the deflection element 83. The interference light (200c, 200Rc) deflected by the deflection element 83 is stretched or expanded 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 stretched or expanded by the deflection element using a function normalized for 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.

The diameter of the 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 the 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 light beam width in the sub-scanning direction is expanded by deflection by the deflection element 83, thereby achieving wavefront measurement with appropriate resolution.

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 wavefront measuring device 4 according to the present embodiment.

The wavefront measuring device 4 is configured with 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 test object 36 in this embodiment is a molded lens (optical element).

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

In general, 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 aberration due to an inserted lens (aberration caused by variations in the optical path of the light beam). In that case, a wavefront sensor 90 with a screen size approximately the same as the aperture of the test object is required.

Figure 7 shows an example of a signal obtained by the wavefront sensor 90 in this embodiment. In general, 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 with a screen size similar to the aperture 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 Figure 7 (A). In general, 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, under conditions that provide appropriate resolution.

In this embodiment, the deflection element 84 compresses the light beam in a predetermined direction (the vertical direction of the wavefront sensor 90) to realize 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 light beam width in a predetermined direction of the light beam of the test light 200b, but this is not limited to this. For example, if the light beam of 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 may be arranged to expand the light 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 (deflection element 84) reduces the light beam width 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 light beam width in the first direction. This allows the lateral light receiving area (light receiving surface) of the wavefront sensor 90 to be effectively utilized.

Next, a method for manufacturing an optical system in the 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 in this embodiment. For example, the results of a wavefront measured using the wavefront measuring device 1 in the first embodiment or the wavefront measuring device 2 in the second embodiment can be fed back to a method for manufacturing an optical system (test object 30).

First, in step S101, an optical system is assembled using optical elements, and the position of each element is adjusted (optical system assembly adjustment). Next, in step S102, the optical performance (optical precision) 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 sufficient in step S102, this flow relating to the manufacturing method of the optical system is terminated.

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

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 appropriate resolution while suppressing the size of the light receiving unit.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments, and various modifications and variations are possible within the scope of the gist of the invention.

1 Wavefront measuring device 80, 81 Deflection element (deflection unit)
90, 91 Wavefront sensor (light receiving unit)
100 Computer (calculation unit)

Claims (10)

a deflection unit that deflects a first light beam incident via a test object to increase a beam width of the first light beam 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 according to claim 1, characterized in that the second direction is perpendicular to the first direction. The wavefront measuring device according to claim 1 or 2, characterized in that the light receiving unit has a microlens array. The wavefront measuring device according to any one of claims 1 to 3, characterized in that the light receiving unit has a Hartmann mask. The wavefront measuring device according to any one of claims 1 to 4, characterized in that the light receiving unit is an image sensor. A wavefront measuring device according to any one of claims 1 to 5, characterized in that the first light before entering the deflection section has a beam width in the first direction that is smaller than the beam width in the second direction. The wavefront measuring device according to any one of claims 1 to 6, characterized in that the deflection unit is a diffraction grating. A step of expanding a beam width of the first light in a first direction by deflecting the first light that has been incident on a deflection unit via a test object;
receiving, by a light receiving unit, the second light deflected by the deflection unit;
and calculating a wavefront of the first light before it is incident on the deflection section based on an output of the light receiving section. A method for manufacturing an optical system, comprising the steps of:
Assembling the optical system;
A step of expanding a beam width of the first light in a first direction by deflecting the first light incident on a deflection unit via the optical system;
receiving, by 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;
and evaluating the optical performance of the optical system based on the wavefront. A method for manufacturing an optical element, comprising the steps of:
molding the optical element;
A step of expanding a beam width of the first light in a first direction by deflecting the first light incident on a deflection unit via the optical element;
receiving, by 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;
and evaluating the optical performance of the optical element based on the wavefront.