JPWO2015146506A1 - Phase filter, imaging optical system, and imaging system - Google Patents

Abstract

An object of the present invention is to avoid a change in the center of gravity of a point spread function, and to suppress the occurrence of an image defect due to an optical axis rotation shift in a phase filter. In the phase filter 101, the present invention includes a plurality of annular zones 111 that are rotationally symmetric with respect to the optical axis, and each annular zone 111 has a cross-sectional shape defined by a concave or convex substantially parabola. At least one of the annular zones 111 has a maximum depth in a concave cross-sectional shape defined by a substantially parabola or a maximum height in a convex cross-sectional shape defined by a substantially parabola. A phase greater than the wavelength shall be given.

Description

  The present invention relates to an imaging system to which a technique for expanding the depth of field or the depth of focus is applied, a phase filter used therefor, and an imaging optical system.

=== Import by reference ===
This application claims the priority of Japanese Patent Application No. 2014-65542 filed on March 27, 2014, and is incorporated herein by reference.
In the pupil plane of the imaging camera optical system, by giving a phase distribution given by a point spread function (hereinafter referred to as PSF) to the coordinates in the pupil plane, the blur of the point image with respect to the defocus is made uniform. A technique called Wavefront Coding (hereinafter abbreviated as WFC) for removing uniform blur by image processing called deconvolution to expand the depth of field and the depth of focus of an optical system has been proposed (see Patent Document 1). ing.

  It also uses a diffuser with a scattering function that diffuses light representing the scene and does not depend on the coordinates of the aperture, a sensor that receives the light representing the diffused scene and generates data representing the image, and a point spread function. In addition, a system including a hardware processor that removes image blur (see Patent Document 2) has been proposed.

US Pat. No. 5,748,371 Special table 2013-518474 gazette

  However, in the above-described WFC technology, when the phase modulation optical phase filter has a non-rotationally symmetric structure with respect to the optical axis, a problem corresponding to that occurs. That is, there arises a problem that the center of gravity of the PSF moves depending on the shift amount (defocus amount) from the in-focus position. Further, with this problem, there is also a problem that a ghost image having a directivity is generated when the modulation due to the optical phase filter is removed from the modulated intermediate image by signal processing. Furthermore, since the optical phase filter has a rectangular shape (see FIG. 21), the shape of the diaphragm needs to be rectangular, so that a severe accuracy is required for adjusting the optical axis between the diaphragm, the optical phase filter, and the lens. Therefore, there is a problem that the tolerance of the design error of the entire optical system is reduced.

  On the other hand, even in the case of using a rotationally symmetric optical phase filter, in the prior art, since the shape of the phase plate is determined by a stochastic model based on statistical optics, the shape of the diffuser cannot be uniquely determined. There are still problems in manufacturing such as it is difficult to clearly define the dimensional accuracy.

  Accordingly, an object of the present invention is to obtain a high-quality image by suppressing deterioration in image quality due to a ghost or the like in a phase filter, an imaging optical system, and an imaging system for enabling expansion of depth of field or depth of focus. It is to provide a suitable technique.

  The phase filter of the present invention that solves the above problems includes a plurality of annular zones that are rotationally symmetric with respect to the optical axis, each annular zone having a cross-sectional shape defined by a concave or convex substantially parabola, At least one of the annular zones has a maximum depth in a concave cross-sectional shape defined by the substantially parabola, or a maximum height in a convex cross-sectional shape defined by the substantially parabola, It provides a phase of one wavelength or more of incident light.

  The imaging optical system of the present invention includes a plurality of annular zones that are rotationally symmetric with respect to an optical axis, and each of the annular zones has a cross-sectional shape defined by a concave or convex substantially parabola, At least one of the bands has a maximum depth in a concave cross-sectional shape defined by the substantially parabola or a maximum height in a convex cross-sectional shape defined by the substantially parabola. A phase filter that gives a phase of one wavelength or more is mounted on the imaging optical system.

  The imaging system of the present invention includes a plurality of annular zones that are rotationally symmetric with respect to an optical axis, and each annular zone has a cross-sectional shape defined by a concave or convex substantially parabola, and each annular zone At least one of the ring zones has a maximum depth in a concave cross-sectional shape defined by the substantially parabola or a maximum height in a convex cross-sectional shape defined by the substantially parabola. Deconvolution image processing is performed on an image captured by an imaging optical system in which a phase filter that gives a phase of one wavelength or more is mounted on the imaging optical system. According to such a configuration of the present invention, it is possible to avoid a change in the center of gravity of the point spread function and to suppress the occurrence of an image defect due to the rotational deviation of the optical axis in the phase filter.

  According to the present invention, it is possible to obtain a high-quality image while suppressing deterioration in image quality due to a ghost or the like.

It is a schematic diagram of the imaging optical system carrying the phase filter of this embodiment. It is a top view which shows the structural example 1 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 1 of the phase filter in this embodiment. It is a top view which shows the structural example 2 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 2 of the phase filter in this embodiment. It is sectional drawing explaining the ring zone structure example 1 in this embodiment. It is a figure which shows the comparative example 1 of PSF and the prior art in the phase filter of this embodiment. It is a figure which shows the structural example of the imaging system using the phase filter of this embodiment. It is a top view which shows the structural example 3 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 3 of the phase filter in this embodiment. It is a figure which shows the relationship between the conic curve and offset in the cross-sectional structure of the ring zone of this embodiment. It is sectional drawing explaining the zone structure example 2 in this embodiment. It is a figure which shows the example of PSF in a prior art. It is a figure which shows the example of PSF in the phase filter of this embodiment. It is a top view which shows the structural example 4 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 4 of the phase filter in this embodiment. It is a top view which shows the structural example 5 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 5 of the phase filter in this embodiment. It is a top view which shows the structural example 6 of the phase filter in this embodiment. It is a sectional side view which shows the structural example 6 of the phase filter in this embodiment. It is a figure which shows the conventional cubic function phase plate.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram of an imaging optical system 150 on which the phase filter 101 of this embodiment is mounted. FIG. 2 is a plan view showing a structural example 1 of the phase filter 101 in this embodiment. FIG. 3 is a side sectional view showing Structural Example 1 of the filter 101. FIG. Note that the phase filter 101 and the imaging lens 102 included in the imaging optical system 150 shown in FIG. 1 both show the shape of a side section.

  As shown in FIGS. 1 to 3, the phase filter 101 has a disk-like outer shape and a rotationally symmetric shape around the optical axis 1. Further, in this phase filter 101, grooves having a substantially parabolic cross section, that is, concave surfaces 112 are formed in a plurality of rows at substantially equal intervals concentrically around the optical axis 1 described above. The concave surface 112 formed concentrically around the optical axis 1 in this manner is referred to as an annular zone 111, and the annular zone 111 and the like are collectively referred to as an annular zone structure 110. In the example of the phase filter 101 shown in FIG. 1, an annular structure 110 including only two rows of annular zones 111 is shown for the sake of simplicity of explanation. Actually, like the phase filter 101 of FIGS. 2 to 3, it has a ring zone structure 110 composed of a multi-row ring zone 111 (two or more rows).

  The above-described annular zone 111 becomes a concave surface that acts as a concave lens in the radial direction of the pupil plane with respect to the light incident on the annular zone 111. Note that the width of the annular zone 111 in the phase filter 101 shown here is equal between the annular zones. On the other hand, as shown in FIGS. 4 and 3, it is also possible to adopt a case where the cross-sectional shape of the annular zone 111 is not a concave shape but a convex shape. In this case, the phase filter 101 includes a plurality of convex surfaces 113 having a substantially parabolic shape and a convex cross-sectional shape formed in a plurality of rows concentrically around the optical axis 1 described above at substantially equal intervals. Accordingly, the annular zone 111 in this case is a convex surface that acts as a convex lens in the radial direction of the pupil plane with respect to the light rays incident on the annular zone 111.

  On the other hand, in the imaging optical system 150, the imaging lens 102 is disposed so that the phase filter 101 and the optical axis 1 are shared. The imaging lens 102 is a lens that can form an image of the object space at a predetermined position on the optical axis 1 when the phase filter 101 is not provided. By forming the imaging optical system 150 with a configuration in which the phase filter 101 is combined with the imaging lens 102, the light beam 103 (incident light beam) incident on the phase filter 101 is refracted by the concave surface 112 (or convex surface 113) described above, It becomes divergent light locally. The curvature of the concave surface 112 (or convex surface 113) of the phase filter 101 is set so that the diverging light becomes a locally substantially parallel light beam (on the paper surface) by the imaging lens 102. The phrase “substantially parallel” refers to a state in which the light rays of each concave surface 112 (or convex surface 113) that have passed through each concave surface 112 (or convex surface 113) are substantially parallel after passing through the imaging lens 102.

  The propagation direction of the local substantially parallel light beam is directed to the original focal position 3 along the refraction direction of the light beam 2 passing through the center of the annular zone 111. This is because a virtual tangential plane with respect to the concave surface 112 (or convex surface 113) at the center of the annular zone 111 is perpendicular to the optical axis 1 of the imaging lens 102, and the light beam passing therethrough is not refracted by the phase filter 101. This is because, since it is incident on the image lens 102, it is clear that the light beam passes through the focal position 3 when the phase filter 101 is not provided. As described above, the substantially parallel light fluxes from the plurality of annular zones 111 overlap in the range 104 in the optical axis direction in the vicinity of the focal point 3. For convenience of explanation, the light beam diverging and refracted by the imaging lens 102 from each annular zone 111 has been described as a substantially parallel light beam. However, since the light beam is actually rotationally symmetric about the optical axis 1, The propagation form is a light beam propagating along the side surface of the cone. By overlapping a plurality of such light beams at different angles, a plurality of non-diffracted beams are overlapped to achieve smoothing of the point image distribution in the focal direction.

  In the phase filter 101 illustrated in FIGS. 2 and 3, the approximate shape of the cross section of each annular zone 111 is represented by a conic indicated by (Equation 1).

  Here, y is the depth, x is the height or position in the ring zone, R is the radius of curvature, κ is the conic constant, and when κ = 1, this equation becomes a parabola. The uneven shape of the annular zone 111 may be concave as shown in FIGS. 2 and 3 or convex as shown in FIGS.

  When the cross-sectional shape in the annular zone 111 is approximated by a parabola, the contribution to the PSF in each annular zone 111 can be expressed by the following equation.

となる。どの輪帯１１１のＰＳＦへの寄与もデフォーカスＷ２０に対して略不感にできることが分かる。そこで、本実施形態の輪帯１１１における断面形状は、κ＝−１として、放物線形状を成し、直径３０ｍｍ、焦点距離５０ｍｍのレンズに対し、輪帯１１１の数を５０とした構造を採用した。また図６にて示すように、各輪帯１１１の幅はすべて同じであり、各輪帯１１１が与える位相が、入射光の波長の２倍すなわち２λになるよう、輪帯１１１の断面形状における高さ（断面底部１２０から輪帯１１１の表面１２１までの高さ）を設定している。Here, PSFi represents the contribution of the i-th annular zone 111 to the PSF. J0 (•) is a 0th-order first-order Bessel function, ρ is the diameter of the PSF, W20 is the defocus amount, and ξi is the diameter of the i-th annular zone 111. Although the Bessel function is an oscillation function, when the oscillation of the phase term of the integrand is sufficiently faster than the oscillation of the Bessel function, a stationary phase approximation solution can be applied. This application condition is that the height in the cross-sectional shape of the annular zone 111 (the height from the cross-section bottom 120 to the surface 121 of the annular zone 111) corresponds to several times the wavelength λ of the incident light to the phase filter 101. To establish. Here, the wavelength λ of the incident light is assumed to be a representative value in the wavelength region when having a wavelength region width like white light. In this case, when the contribution to the PSF in each annular zone 111 is calculated by the stationary phase approximate solution,

It becomes. It can be seen that the contribution of any annular zone 111 to the PSF can be made almost insensitive to the defocus W20. Therefore, the cross-sectional shape of the annular zone 111 of this embodiment is a parabolic shape with κ = −1, and a structure in which the number of the annular zones 111 is 50 is adopted for a lens having a diameter of 30 mm and a focal length of 50 mm. . Further, as shown in FIG. 6, the width of each annular zone 111 is the same, and the phase given by each annular zone 111 is twice the wavelength of incident light, that is, 2λ, in the sectional shape of the annular zone 111. The height (height from the cross-section bottom 120 to the surface 121 of the annular zone 111) is set.

  FIG. 7 is a diagram showing the PSF in the optical axis direction calculated using the phase filter 101 of the present embodiment and assuming that the object to be imaged is 1 m from the optical system. Here, a PSF when the phase filter 101 of the present embodiment is employed and a PSF in a conventional optical system that does not use the phase filter 101 of the present embodiment are shown together. As is clear from the example of FIG. 7, in the conventional optical system, the relationship between the position in the optical axis direction and the PSF is very sensitive, the position on the optical axis shifts even a little, and the defocus increases even a little. Then, while the PSF changes rapidly, when the phase filter 101 of the present embodiment is employed, the PSF can be kept substantially constant over a wide range.

  In the phase filter 101 of the present embodiment, since the entire PSF corresponds to the sum of contributions of each annular zone 111 to the PSF, the height (depth) of the sectional shape of each annular zone 111 is set to the wavelength λ of incident light. By configuring so as to give the above maximum optical path difference, the depth of focus of the PSF contribution of each annular zone 111 becomes deep.

  Note that the phase filter 101 in this embodiment can employ quartz glass having a refractive index n1 as a material. In this case, an unevenness is formed as a cross-sectional shape of each annular zone 111 by using an existing pattern forming technique and etching technique for quartz glass. Of course, as a manufacturing technique of the phase filter 101, other than that, the groove shape is formed on the quartz glass using a high hardness cutting tool such as diamond, so that the sectional shape of each annular zone 111 is uneven (particularly, A technique for forming a concave groove) may be employed. Furthermore, the phase filter 101 may be formed by forming a thick plate having unevenness as a mold and performing plastic injection molding using this mold. Alternatively, the phase filter 101 may be formed on a transparent flat substrate by disposing a convex member or a concave member having a refractive index n1 in a ring shape centered on the optical axis. In any case, since the phase filter 101 of the present embodiment has a rotationally symmetric shape with the optical axis as the center, the above-described processing can be created by appropriately adopting conventional processing techniques, and the efficiency in manufacturing can be improved. The labor is improved compared to the production of the rectangular phase filter.

  Next, a configuration of the imaging optical system 150 using the phase filter 101 of the above-described embodiment and an imaging system 300 that performs image processing on an image captured by the imaging optical system 150 will be described with reference to FIG. . Here, it is assumed that the object 301 exists at a relatively short distance from the imaging optical system 150 and the object 302 exists at a far distance. In the imaging optical system 150, the front lens group 151 that condenses the reflected light of the objects 301 and 302, the phase filter 101 of the present embodiment that processes the light collected by the front lens group 151 as incident light, A diaphragm 152 that is behind the phase filter 101 and adjusts the amount of light (circular in accordance with the phase filter 101), a rear lens group 153 that processes light adjusted by the diaphragm 152 (that is, the imaging lens 102), At least.

  In this case, the reflected light of the object 301 and the object 302 is incident on the phase filter 101 via the front lens group 151 in the imaging optical system 150, and the light from the phase filter 101 is transmitted to the aperture 152 and the rear lens group. It enters the rear lens group 153 via 153 and forms images 303 and 304 that are uniformly blurred in the direction of the optical axis 1 (by the above-described smoothing of the point image distribution in the focal direction). Therefore, the imaging system 300 has a configuration in which the image sensor 305 is disposed at a position where the images 303 and 304 and the like overlap in the optical axis direction.

  In addition, the imaging system 300 converts the output signal from the image sensor 305 described above into an appropriate still image or video image format and outputs it as an image signal while maintaining the highest resolution information that can be output by the image sensor 305. An image signal output circuit 306 is provided. In addition, the imaging system 300 includes a monitor output generation circuit 307 that receives the image signal output from the image signal output circuit 306, converts the image signal into a format that can be displayed on the display, and outputs the image signal on the monitor display 308. The images displayed on the monitor display 308 are images 303 and 304 in which the near object 301 and the distant object 302 are uniformly blurred, as schematically shown in FIG. However, since such monitor output processing is not essential for the imaging system 300, there is no problem even if the monitor display 308 and the monitor output generation circuit 307 are not included.

  In addition, the imaging system 300 includes a deconvolution preprocessing circuit 309 and a deconvolution filter circuit 310. In the imaging system 300, the output signal from the image signal output circuit 306 described above is branched and input to the deconvolution preprocessing circuit 309. As a result, the deconvolution preprocessing circuit 309 converts the digital image data format suitable for the filter operation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the second monitor output generation circuit 311. The second monitor output generation circuit 311 converts the input signal from the deconvolution filter circuit 310 into an arbitrary general still image or moving image format, and outputs and displays it as an output signal on the second monitor display 312. When output display is performed on the second monitor display 312, the above-described image focused on both the close object 301 and the distant object 302 is output. At this time, since the phase filter 101 is used, in the output image on the second monitor display 312, the image position of the object does not deviate depending on the distance from the imaging optical system 150, and the objects 301 and 302. An image is formed at a position reflecting the original position.

  Subsequently, there is provided a structure in which the cross-sectional bottom 120 in the concave or convex cross-sectional shape is offset by a predetermined height in the radial direction of the pupil plane with respect to the incident light between at least one of the above-mentioned respective annular zones 111. The configuration will be described. In such a configuration, the PSF is further homogenized not only by the effect of the annular zone 111 having a substantially parabolic shape in cross section but also by the effect of adding the height offset as described above to each annular zone 111.

  FIG. 9 is a plan view showing Structural Example 3 of the phase filter 101 in the present embodiment, and FIG. 10 is a side sectional view of the same. As illustrated here, between the annular zones 111, the cross-sectional bottom 120 in the cross-sectional shape is offset by a predetermined height in the radial direction of the pupil plane with respect to the incident light. The relationship between the conic curve (substantially parabola) corresponding to the cross-sectional structure of each annular zone 111 and the offset is as shown in FIG. Regardless of whether the cross-sectional shape is concave or convex, the separation distance (height) between the cross-sectional bottom 120 of each annular zone 111 and the cross-sectional bottom 122 of the adjacent annular zone 111 is defined as the offset distance.

  In the example of FIG. 10, the above-described offset is made in the direction from the back surface (surface from which incident light is emitted) of the phase filter 101 toward the surface 121 of the phase filter 101, and the cross-sectional shape closest to the phase filter central axis 105 is obtained. An offset 107 is generated in total from the cross-section bottom 120 to the cross-section bottom 120 in the cross-sectional shape closest to the phase filter outer edge 106. As illustrated in FIG. 12, the phase given to the 50 annular zones 111 in the phase filter 101 by the height defined by the conic curve is 2λ (twice the wavelength of the incident light). Is set. Each annular zone 111 in this example is given an offset that gradually increases from 0 to λ, that is, monotonously increases from the phase filter central axis 115 toward the outer edge 106.

  As illustrated in FIGS. 15 and 16, in each annular zone 111 of the phase filter 101, an offset that gradually increases from λ to 0, that is, monotonously decreases from the phase filter central axis 115 toward the outer edge 106. It may be a given configuration. In addition, as illustrated in FIGS. 17 and 18, the offset in each annular zone 111 does not simply increase or decrease as it goes from the phase filter center axis 115 toward the outer edge 106, but is simply increased or decreased. The offsets may be replaced at random (however, the total offset 107 between the annular zones 111 is the same as the total offset when the offset is simply increased or decreased).

  Here, the effect of the phase filter 101 configured as described above in consideration of the offset will be described. FIG. 13 is a diagram showing an example of a PSF in the prior art, and FIG. 14 is a diagram showing an example of a PSF in the phase filter of this embodiment. In FIG. 7, the absolute value of the contribution to the PSF in each annular zone 111 is added to show the effect, but here, the calculation result including the phase is shown. A normal imaging optical system such as a camera is an incoherent optical system in a wide wavelength range, and the contribution to the PSF in each annular zone 111 is not examined including the phase, but here, a uniform and stable PSF is used. The result of addition in consideration of the phase is shown. FIG. 13 shows the PSF in the optical axis direction when the above-described offset is not set, and FIG. 14 shows the PSF in the optical axis direction when the offset is given.

  In an incoherent optical system with a wide wavelength range, these are averaged over a wide wavelength range, and even if the light is conceived from one point, the coherency is low, so the vibration of the PSF is greatly relaxed. It can be seen that the PSFs in the prior art illustrated in FIG. 13 are concentrated at zero defocus, whereas the PSFs illustrated in FIG. 14 are distributed over a wide range of defocuses. Therefore, a more stable PSF can be obtained in the phase filter 101 to which an offset is applied between the annular zones 111.

  In addition, although the example in which the width | variety in all the ring zones 111, ie, the zone width, was constant was demonstrated until the above-mentioned, adjusting each zone component of PSF by setting a different zone width for every zone. Can do. FIG. 19 is a plan view showing a structural example 6 of the phase filter 101 in the present embodiment, and FIG. 20 is a side sectional view of the same. As illustrated in FIGS. 19 and 20, the ring zone width 108 in the phase filter 101 is monotonously decreased from the phase filter central axis 115 toward the outer edge 106, thereby reducing the area of the ring zone 111. It can be made substantially constant, and each ring zone component of the PSF can be adjusted.

  Although the best mode for carrying out the present invention has been specifically described above, the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention.

  According to this embodiment, it is possible to avoid the change of the center of gravity of the PSF depending on the defocus amount in principle. Further, PSF is also rotationally symmetric and isotropically expanded, so that a restored image by signal processing does not have directionality, and adverse effects due to optical axis rotation deviation in the phase filter can be suppressed. Further, the fact that PSF is rotationally symmetric leads to a reduction in the amount of processing data, it is possible to reduce the memory for storing the coefficient matrix used for signal processing, and to downsize the signal processing circuit. Furthermore, the fact that the shape of the phase filter is rotationally symmetric makes it possible to create the mold used for molding by rotary lathe processing, which can reduce processing time and manufacturing costs compared to rectangular phase filters. It becomes.

  Therefore, it is possible to avoid a change in the center of gravity of the point spread function and to suppress the occurrence of an image defect due to the optical axis rotation shift in the phase filter. As a result, according to the present embodiment, it is possible to acquire a high-quality image while suppressing image quality degradation due to ghost or the like. In addition, such a high-quality image can be acquired at a low cost.

  At least the following will be clarified by the description of the present specification. That is, in the phase filter of the present embodiment, the bottom position in the concave or convex cross-sectional shape between at least one of the annular zones is a predetermined height in the radial direction of the pupil plane with respect to incident light. An offset structure may be provided.

  According to this, it becomes possible to achieve further homogenization of the PSF, and the image quality after deconvolution can be further improved.

  Further, the phase filter of the present embodiment may have a structure in which the height of the offset is different between the annular zones.

  According to this, it becomes possible to further homogenize the PSF, and the image quality after deconvolution can be further improved.

  Further, the phase filter of the present embodiment may have a structure in which the height of the offset between the annular zones monotonously increases or decreases monotonously from the optical axis toward the peripheral edge of the phase filter.

  According to this, the efficiency of the annular zone formation in the phase filter is improved, and it becomes possible to achieve further homogenization of the PSF under excellent manufacturing cost and efficiency.

  In the phase filter of the present embodiment, the width of the annular zone may be equal between the annular zones.

  According to this, the efficiency of the annular zone formation in the phase filter is improved, and the cost and time for manufacturing the phase filter can be reduced.

Claims (7)

  A plurality of annular zones rotationally symmetric with respect to the optical axis, each annular zone has a cross-sectional shape defined by a concave or convex substantially parabola, and at least one of the annular zones is The maximum depth in the concave cross-sectional shape defined by the substantially parabola or the maximum height in the convex cross-sectional shape defined by the substantially parabola gives a phase of one wavelength or more of incident light. There is a phase filter.   2. The structure according to claim 1, further comprising a structure in which a bottom position in the concave or convex cross-sectional shape is offset by a predetermined height in a radial direction of the pupil plane with respect to incident light between at least one of the annular zones. The phase filter as described.   The phase filter of Claim 2 provided with the structure where the height of the said offset differs between each annular zone.   4. The phase filter according to claim 3, comprising a structure in which the height of the offset between the annular zones monotonously increases or decreases monotonously from the optical axis toward the peripheral edge of the phase filter.   The phase filter according to claim 1, wherein the width of the annular zone is equal between the annular zones.   A plurality of annular zones rotationally symmetric with respect to the optical axis, each annular zone has a cross-sectional shape defined by a concave or convex substantially parabola, and at least one of the annular zones is The maximum depth in the concave cross-sectional shape defined by the substantially parabola or the maximum height in the convex cross-sectional shape defined by the substantially parabola gives a phase of one wavelength or more of incident light. An imaging optical system in which a phase filter is mounted on the imaging optical system.   A plurality of annular zones rotationally symmetric with respect to the optical axis, each annular zone has a cross-sectional shape defined by a concave or convex substantially parabola, and at least one of the annular zones is The maximum depth in the concave cross-sectional shape defined by the substantially parabola or the maximum height in the convex cross-sectional shape defined by the substantially parabola gives a phase of one wavelength or more of incident light. An imaging system that performs deconvolution image processing on an image captured by an imaging optical system in which a certain phase filter is mounted in an imaging optical system.

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