JP6516134B2 - Filter, lens, imaging optical system and imaging system having phase conversion function - Google Patents

Description

  The present invention relates to a technique for extending the depth of field of a real or virtual image produced by an optical system. In particular, the present invention relates to a lens, a contact lens, an intraocular lens, an imaging optical system, an eyepiece optical system, and an imaging system to which WFC (wave-front coding) or EDOF (Extended Depth of Field) technology can be applied.

  WFC and EDOF techniques are techniques that use a phase filter together with an optical system for the purpose of extending the depth of field of an imaging optical system without deteriorating the brightness of an image. (See Patent Document 1, Non-Patent Document 1, etc.)

As a phase function describing the phase filter distribution, an orthogonal cubic function, namely, Cubic Phase Mask (CPM) has been proposed. (Non-patent document 1)
Furthermore, to further extend the depth-of-field extension, a polynomial represented by ax ³ + by ³ + cx ² y + d xy ² as a phase function or r ³ cos ( ³ q) which is one of Zernike polynomials Proposed. (Patent Document 4) In addition, various phase function attempts have been reported to improve the depth of field extensibility. (See Non-Patent Documents 2 to 11 etc.)

  Further, as a method of extending the depth of field, a method of dividing the lens aperture into a plurality of annular zones has been reported. (Patent Document 5)

  There are also reports on the chromatic aberration generated by the target phase filter and optical system. (Non-patent documents 12, 13 and 14)

  It has also been proposed to apply the function of the phase filter to contact lenses, corneal deformation processing, and intraocular lenses. (Patent Documents 2 and 3)

There is also a report of depth extension considering the depth in the back and forth direction with respect to the conjugate position. (Patent Document 6)
The method of calculating point image distribution from the pupil function of incoherent optical system is a known technique. (Non-Patent Document 15)
The relationship between overcorrection of the spherical aberration of the optical system and two-line blurring has also been reported. (Non-Patent Document 16)
The achromatic condition of the prism is also a known technique. (Non-Patent Document 17)

U.S. Patent No. 5,748,371 US Patent 6536898 US Patent 7025454 Patent Publication WO / 1999/057599 JP, 2009-271537, A JP, 2012-253602, A

E. R. Dowski, Jr., and W. T. Cathey, Extended depth of field through wave-front coding, Appl. Opt. 34, 1859-1866 (1995) W. L. Chi and N. George, “Electronic imaging using a logarithmic asphere,” Opt. Lett. 26, 875-877 (2001) Sherif S. Sherif, W. Thomas Cathey, and Ed R. Dowski, "Phase plate to extend the depth of field hybrid technology systems", Appl. Opt. Vol. 43, 2709-2721 (2004) Zhao, Hui; Li, Yingcai, "Performance of an improved logarithmic phase mask with optimized parameters in a wave front-coding system," Appl. Opt, Vol. 49 229-238 (2010) Albertina Castro and Jorge Ojeda-Castaneda, "Asymmetric phase masks for extended depth of field," Appl. Opt. Vol. 43, 3474-3479 (2004) J. Ojeda-Castaneda "Annular phase-only mask for high focal depth," Optics letters, Vol. 30, No. 13, pp. 1647-1649 (2005) Q. Yang, L. Liu, and J. Sun, Opt. Commun. 272, 56 (2007) N. Caron and Y. Sheng, Appl. Opt. 47, E39 (2008). Feng Zhou, Guangwei Li, Haitao Zhang, and Dongsheng Wang, "Rational phase mask to extend the depth of field in optical-digital hybrid imaging systems," OPTICS LETTERS, Vol. 34, 380-382 (2009) Yasuhisa Takahashi and Shinichi Komatsu, "Optimized free-form phase mask for extension of depth of field in wave front-coded imaging," OPTICS LETTERS, Vol. 3, 1515-1517 (2008) Shuai Yuan and Chrysanthe Preza, "Point-spread function engineering to reduce the impact of spherical aberration on 3D computational fluorescence microscopy," Optics Express. Vol.19, 23298-23314 (2011) Wach, Hans B; Dowski jr, Edward R; Cathey, W Thomas, "Control of Chromatic Focal Shift Through Wave-Front Coding," Appl. Optics, Vol. 37, 5359-5367 (1998) Hans B. Wach, Edward R. Dowski, Jr., and W. Thomas Cathey, "Channel reduction and applications to image processing," Appl. Opt. Vol. 39, 1794-1798 (2000) Rongfu Zhang and Kang Lu, "Variations in the point spread function characteristics of wavelengths for a wave front coding imaging system," Opt. Letters, Vol. 36, 4647-4649 (2011) J. W. Goodman: "Introduction to Fourier Optics" (McGraw-Hill, 1968) Toshio Ogura: "Contemporary Camera and Lens Technology", Photography Industry Publishing Company (1982) Yamada Kogoro "Geometrical Optics" Optical Industry Research Association (1981)

  Among the phase functions shown in the above reference list, the point spread function (PSF) corresponding to the function similar to the orthogonal cubic function Cubic Phase Mask (CPM) also tends to be distributed in a linear manner, and the phase filter Deterioration is noticeable in the affected image. It results in an image that has a so-called blur pattern and a pattern not found in the original object.

  Although a method of dividing the lens aperture into a plurality of annular zones has been reported (Patent Document 5), the discontinuous boundary in the lens aperture causes flare and stray light, and in particular, good results can be obtained in image processing Makes it difficult.

  When making a phase change into a rotationally symmetric function without a discontinuous boundary, a point spread function (PSF) may generate a ring-shaped concentrated portion.

  In the prior art, while having a sufficient depth-of-field extension function, the point spread function (PSF) does not become a straight line or an undesirable pattern, and a phase function is created considering the position before and after the conjugate distance No guidance was given.

  No optical guidelines have been shown to reduce the occurrence of chromatic aberrations due to phase filters.

  The problem to be solved by the present invention is that, in a phase filter used together with an optical system, a point image distribution produced by the optical system while having a function of enlarging the depth of an image produced by the optical system. Providing a means to realize a depth-of-field extended phase filter that does not generate an unnatural light concentration such as a straight line in the function (PSF) and at the same time does not include discontinuous boundaries in its effective surface It is.

  The problem to be solved at the same time is to present a guideline for changing the setting of the function according to the specification of the optical system using the phase function.

  A further problem to be solved is to present conditions for keeping the chromatic aberration generated by the phase filter small.

  The means for solving the problem that an unnatural light concentrated portion such as a straight line is generated in the point spread function (PSF) described above centers the optical axis on the phase function that changes the wavefront passing through the optical system. The spiral, circumferential or radial shape distribution, or "rotational component" is included as appropriate. In addition, by making the phase value width of the peripheral region of the aperture larger than the phase value width of the central region, the distribution of the point spread function (PSF) is more concentrated in the central portion.

  Discontinuous boundaries in the above-mentioned effective surface are removed by smoothing the phase distribution formally.

  The means for preventing the occurrence of the ring-shaped concentration described above calculates the point spread function (PSF) in the state where the phase filter equipped with the conditions presented in the present invention is attached to the used optical system at design If band concentration is observed, change it to a phase distribution that avoids this.

  In order to create a phase function in consideration of the position before and after the above conjugate distance, the relationship between the phase distribution and the depth of field extension presented in Patent Document 6 is used as a guideline.

  In order to suppress the occurrence of the chromatic aberration caused by the above phase filter, a plurality of phase filters made of materials having different optical dispersion values are used in combination so as to satisfy the condition presented in Non-Patent Document 17.

  According to the present invention, a phase filter, a lens, and a lens having a phase conversion function that avoids undesirable blurring at the same time as the depth of field simultaneously, avoids an origin of generation of light noise, and minimizes chromatic aberration caused by the phase filter. It is possible to realize an imaging optical system and an imaging system.

It is a whole block diagram of an imaging system. It is a figure for demonstrating a coordinate system and a pupil function. It is a schematic diagram which shows the mode of the light ray which passes through the center part and peripheral part of a pupil. It is a figure of phase distribution of Cubic Phase Mask (CPM), and its point spread function (PSF). It is a figure of phase distribution which multiplied distance r from a central point to CPM, and its point spread function (PSF). It is a figure of the phase distribution which multiplied the square of the distance r from the central point to CPM, and its point spread function (PSF). It is a figure of phase distribution which multiplied 3rd power of distance r from a central point to CPM, and its point spread function (PSF). It is a figure of an example of the single-strand spiral phase distribution which is Embodiment group 1, and its point spread function (PSF). FIG. 9 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the distance r from the central point and its point spread function (PSF). FIG. 9 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the square of a distance r from the center point and a point spread function (PSF) thereof. FIG. 9 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the third power of the distance r from the center point, and its point spread function (PSF). FIG. 9 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the fourth power of the distance r from the center point and the point spread function (PSF) thereof. It is a figure of the phase distribution which halved the amount of rotations of FIG. 12, and its point spread function (PSF). FIG. 13 is a diagram of a phase distribution and its point spread function (PSF) in which the distance from the center point is a plane when the distance from the central point is 0 to 1/2 of the effective diameter, and the peripheral portion is the same function as FIG. FIG. 14 is a diagram of a phase distribution and its point spread function (PSF) in which the distance from the central point is a plane when the distance from the central point is 0 to 1/2 of the effective diameter, and the peripheral portion is the same function as FIG. It is a figure of an example of the six-line spiral phase distribution of Embodiment group 2, and its point spread function (PSF). FIG. 17 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the distance r from the central point and its point spread function (PSF). FIG. 17 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the square of the distance r from the central point and its point spread function (PSF). FIG. 17 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the third power of the distance r from the center point and the point spread function (PSF) thereof. It is a figure of an example of four-row spiral phase distribution, and its point-spread function (PSF). FIG. 7 is a diagram of an example of a four-line helical phase distribution and its point spread function (PSF) when the distance from the central point is 0 to 1/2 of the effective diameter, and the peripheral portion is a four-strip helical phase distribution; FIG. 7 is a diagram of an example of a four-line helical phase distribution and its point spread function (PSF) when the distance from the central point is 0 to 1/3 of the effective diameter, and the periphery is an example of a four-line helical phase distribution. FIG. 7 is a diagram of an example of a four-line helical phase distribution and its point spread function (PSF) when the distance from the central point is 0 to 1⁄4 of the effective diameter, It is a figure of phase distribution which made the direction of turning rotation of FIG. 21 reverse, and its point spread function (PSF). It is a figure of phase distribution which made the amount of rotations twice as large as phase distribution of Drawing 21, and its point spread function (PSF). It is a figure of an example of phase distribution of radiation shape, and its point spread function (PSF), without turning. It is a figure of an example of concentric-like phase distribution of Embodiment group 3, and its point spread function (PSF). FIG. 27 is a diagram of the phase distribution obtained by multiplying the phase distribution by the distance r from the center point and its point spread function (PSF). The fluctuation period has been finely adjusted. FIG. 28 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 27 by the square of a distance r from the center point and a point spread function (PSF) thereof. The fluctuation period has been finely adjusted. FIG. 28 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 27 by the cube of the distance r from the center point and the point spread function (PSF) thereof. The fluctuation period has been finely adjusted. FIG. 28 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 27 by the fourth power of the distance r from the center point and the point spread function (PSF) thereof. The fluctuation period has been finely adjusted. 27 is a diagram of a phase distribution close to the phase distribution of FIG. 27 when the distance from the central point is 0 to 1/2 times the effective diameter, and the peripheral portion is an example of a concentric phase distribution and its point spread function (PSF). It is a figure of phase distribution which multiplied distance r from the central point by phase distribution of FIG. 32, and its point spread function (PSF). The fluctuation period has been finely adjusted. FIG. 33 is a diagram of a phase distribution obtained by multiplying the phase distribution of FIG. 32 by the square of a distance r from the center point and a point spread function (PSF) thereof. The fluctuation period has been finely adjusted. It is a figure of phase distribution which multiplied 3rd power of distance r from the central point to phase distribution of Drawing 32, and its point spread function (PSF). The fluctuation period has been finely adjusted. It is a figure of phase distribution which multiplied 4th power of distance r from the central point to phase distribution of Drawing 33, and its point spread function (PSF). The fluctuation period has been finely adjusted. It is a figure of an example of concentric-like phase distribution of embodiment group 3 whose central value is a maximum value, and its point spread function (PSF). FIG. 38 A diagram of a phase distribution whose concentric circle cycle is twice that of the phase distribution of FIG. 37 and its point spread function (PSF). FIG. 38 A diagram of a phase distribution whose concentric circle cycle is three times that of the phase distribution of FIG. 37 and its point spread function (PSF). FIG. 38 is a diagram of a phase distribution whose concentric circle cycle is about four times that of the phase distribution of FIG. 37 and its point spread function (PSF). FIG. 38 A diagram of a phase distribution whose concentric circle cycle is about eight times that of the phase distribution of FIG. 37 and its point spread function (PSF). It is a figure which introduce | transduces an example of the method of dividing phase distribution into the range of a value, and deform | transforming. It is a figure explaining the principle of the chromatic aberration correction in a phase filter. It is a figure explaining a mode that the phase filter is joined. It is a figure which shows an example of a mode that a phase filter is used for an eyepiece optical system. It is a figure for demonstrating the form which implement | achieves a phase filter in a part of eyeball.

[Embodiment]
Hereinafter, an imaging apparatus provided with an imaging optical system will be described as one of the embodiments of the present invention.

  First, the overall configuration of the imaging device will be described. FIG. 1 is a block diagram showing an entire configuration of an imaging apparatus. As shown in FIG. 1, the imaging apparatus includes an imaging optical system 11, a light wavefront conversion element 12, an imaging element, an image processing circuit, and the like. Since the shape of the point spread distribution with the extended depth of field formed by the present invention is good, it may be possible to use it without using the image processing circuit.

  It is desirable that the arrangement position of the light wavefront conversion element 12 be inside or in the vicinity of the imaging optical system 11. A variable optical element may be used as the light wavefront conversion element 12.

  The point spread function (PSF) will be described. The point spread function (PSF) is a distribution on the image plane of an ideal point object, but from the wave-optical point of view, it is also a "incoherent system in which the pupil function is Fourier transformed and its amplitude is squared". It has been known.

  A method of realizing the phase distribution will be described. As a method of realizing the spatial phase change, there are a method using the thickness distribution of the optical member, a method using the thickness distribution of the optical member, and a method using the above two methods simultaneously. Also, a variable optical element such as a spatial phase modulation element may be used.

  The implementation form of the light wavefront conversion element 12 will be described. The light wavefront conversion element is not limited to a planar member, and may be a lens, to which a desired phase distribution is added to a curved surface.

The aperture of the light wavefront conversion element will be described. As a method of designating the position on the opening surface, there are an orthogonal coordinate form shown in FIG. 2A and a polar coordinate form shown in FIG. 2B. The appearance of the opening as viewed from the front is shown in FIG. It can be divided into a central part 21 and a peripheral part 22.
A desirable aperture shape for the light wavefront conversion element is one that does not shield the aperture of the optical system attached and used, and the aperture diameter is not too large compared to the optical system. A circular shape is desirable when used with an optical system having a circular aperture. An example of the function notation of the circular opening is shown in FIG.

  If there are discontinuities in the phase distribution, the discontinuities cause image noise that causes scattering. In order to avoid noise sources, it is desirable to use a function shape that does not have singular points or discontinuous boundaries, or to process discontinuities into smooth shapes.

  The phase value of the phase filter is positive or negative when the phase of a light beam entering parallel to the optical axis at the position to be examined is ahead of the light beam passing through the optical axis position of the phase filter. Be negative. When only the thickness of the optical member acts on the phase, light rays passing thinner than the optical axis undergo positive increase in phase, and light rays passing thicker than the optical axis suffer negative decrease on phase . When only the refractive index distribution of the optical member acts on the phase, a ray passing through a portion having a lower refractive index than the optical axis receives a positive increase in phase and passes a portion having a higher refractive index than the optical axis Rays undergo a negative decrease in phase.

  Various methods can be considered as a method of comparing phase values as regions. To give a few examples, comparison with the value which integrated the size with the set reference value with the area, comparison of average value and dispersion value, comparison of difference of subtracting the minimum value from the maximum value in each range, etc. It can be mentioned.

  In the pupil plane, the central portion refers to an area near the optical axis including the optical axis, and the central portion is a "pupil central portion including the central portion" through which the light beam 32 passes in FIG. The peripheral portion is a "portion surrounding the central portion" through which the light beam 31 passes in FIG.

  As can be seen from FIG. 3, in the imaging optical system, an image formed by a group of rays passing through a portion close to the aperture center has a wider depth of field than a group of rays passing through the aperture peripheral portion. doing. Therefore, the effect on the depth of field is greater for rays passing through the aperture periphery. Furthermore, in the case of the circular opening, the contribution of the peripheral portion is larger than that of the central portion in the area.

  Hereinafter, a design method of the phase distribution will be described. The advantage of using a function in the design of phase distribution is that unique shapes can be shared over the entire manufacturing process, and the imaging performance can be known by calculation before manufacturing. , The point that the design change can be easily performed when there is a need to change the material to be used, the point that the calculation of the dimension of the shape that satisfies the achromatic condition can be easily performed, and There is a point which can also be made extremely easy.

  The advantage of the method of using modeling means in CAD etc. in the design of phase distribution is that the shape which can not be described by a single function, or the distribution with singular points or discontinuous boundaries can be easily corrected to make discontinuities It can be a smooth shape that is not included, and that it is easy to create a distribution that has been modified from the existing distribution. Therefore, the method of using the forming means in CAD or the like is effective in the case of creating a distribution in which functions are connected or a distribution in which it is difficult to create with mathematical expressions.

[Case comparison]
Hereinafter, examples of patterns of phase distribution will be listed, and differences between them will be described.

[Calculation conditions common to each case]
The phase function graph shown below is a stereograph display in which the bottom surface is a square in order to make it easy to identify differences between the two, but when calculating PSF, it is calculated by multiplying the circular aperture coefficient in FIG. It is.

[Example of comparison calculation]
First, a phase function example having components of x ³ + y ³ and its PSF calculation results will be shown as comparison calculation examples for various phase distributions presented hereinafter. (The phase distribution of the pupil function is shown in Fig. 4 (a), PSF is shown in Fig. 4 (b))

    The phase distribution obtained by multiplying this by the distance from the origin, that is, the length r of the radius, is shown in FIG. 5 (a), and the PSF is shown in FIG. 5 (b).

   The phase distribution obtained by multiplying this by the square of the distance r from the origin, ie, the radius r, is shown in FIG. 6 (a), and the PSF is shown in FIG. 6 (b).

   The phase distribution obtained by multiplying this by the third power of the distance r from the origin, ie, the radius r, is shown in FIG. 7 (a) and FIG. 7 (b).

[Embodiment group]
Embodiments of the present invention are presented in three groups, each group including a "rotational component" in its phase distribution shape.
The reason for including this "rotational component" is to prevent the occurrence of linear ones in the distribution of PSF.

  Embodiment group 1 is used to introduce a phase distribution including a single spiral shape. The helical distribution refers to a distribution in which the line connecting the local maxima in the radial direction, the line connecting the local minima in the radial direction, or the line connecting the adjacent equal parts forms a spiral.

  The advantage of using the spiral shape is that the depth distribution can be designed based on the guidelines shown in Patent Document 6, and the PSF shape can be designed independently of the design of the depth distribution.

  FIG. 8 (a) shows a spiral having a distance from the center, that is, a constant distance even if the radius changes, and a distance between the maximum values measured from the center, that is, a constant spiral width. An example of the distribution, FIG. 8 (b) is its PSF.

  FIG. 9A shows a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the distance r from the center point. FIG. 9B is a diagram of the point spread function (PSF).

  FIG. 10A shows a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the square of the length r of the distance from the central point. FIG. 10B is a diagram of the point spread function (PSF).

  FIG. 11A shows a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the third power of the length r from the central point. FIG. 11B is a diagram of the point spread function (PSF).

  FIG. 12A shows a phase distribution obtained by multiplying the phase distribution of FIG. 8 by the fourth power of the length r of the distance from the central point. FIG. 12B is a diagram of the point spread function (PSF).

  By comparing FIGS. 8 to 12 of Embodiment group 1, it is possible to know the change of the PSF shape due to the change of the order of r. It is understood that the case of the embodiment group 1 includes the "rotational component", and the degree of concentration of the PSF in the central portion due to the change of the order of r is larger than that of the comparison form group. The depth of field extension and the order of the phase function are described in US Pat.

  FIG. 13 (a) shows a phase distribution in which the turning amount of FIG. 12 (a) is halved, and FIG. 13 (b) shows its PSF.

  FIG. 14 (a) is a phase distribution where the distance from the center point of FIG. 13 (a) is from 0 to 1/2 of the effective diameter, and the peripheral portion has the same function as FIG. 13 (a). ) Is that PSF.

  FIG. 15 (a) is a phase distribution where the distance from the center point in FIG. 12 (a) is 0 to 1/2 times the effective diameter, and the peripheral portion has the same function as FIG. 12 (a). ) Is that PSF.

  The relationship between the turning amount and the PSF in the single-strand spiral distribution can be known by comparing FIGS. 12 and 13 in the first embodiment group 1 and FIGS. 14 and 15. As the turning amount increases, the shape of the PSF becomes closer to the concentric shape.

  The relationship between the presence of the central flat portion and the PSF in the single-strand spiral distribution can be known by comparison of FIGS. 12 and 15 and FIGS. 13 and 14 in Embodiment Group 1. The presence of a central flat increases the concentration of the PSF at the center.

  Embodiment group 2 is used to introduce the phase distribution of the radiation and multi-strip spiral shape.

  FIG. 16 (a) is an example of a helical phase distribution of six lines, and FIG. 16 (b) is a diagram of its point spread function (PSF).

  FIG. 17 (a) is a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the distance r from the center point, and FIG. 17 (b) is a diagram of the point spread function (PSF).

  18 (a) is a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the square of the distance r from the center point, and FIG. 18 (b) is a diagram of the point spread function (PSF).

  FIG. 19 (a) is a phase distribution obtained by multiplying the phase distribution of FIG. 16 by the third power of the distance r from the center point, and FIG. 19 (b) is a diagram of the point spread function (PSF).

  The comparison of FIGS. 16 to 19 in Embodiment group 2 makes it possible to know the change in PSF shape due to the change in the order of r in the phase distribution of the multi-strip spiral shape. The case of Embodiment group 2 includes the “rotational component” or the “rotational symmetry component”, and it can be understood that the degree of concentration of the PSF in the central portion due to the change of the order of r is larger than that of the comparative form group. The depth of field extension and the order of the phase function are described in US Pat.

  FIG. 20 (a) is an example of a helical phase distribution of four streaks, and FIG. 20 (b) is a diagram of its point spread function (PSF).

  By comparing FIGS. 10, 17 and 20, it is possible to know the change in PSF when the number of threads changes in the helical distribution. As the number of threads increases, PSF becomes closer to rotational symmetry even with a smaller amount of turning.

  Fig. 21 (a) is a phase distribution where the distance from the center point in Fig. 16 (a) is 0 to 1/2 times the effective diameter, and the peripheral portion has the same function as Fig. 16 (a); ) Is that PSF.

  22 (a) shows a phase distribution when the distance from the center point in FIG. 16 (a) is 0 to 1/3 of the effective diameter, and the peripheral portion has the same phase distribution as FIG. 16 (a), FIG. ) Is that PSF.

  FIG. 23 (a) is a phase distribution where the distance from the center point in FIG. 16 (a) is 0 to 1⁄4 of the effective diameter, and the periphery has the same function as FIG. 16 (a); ) Is that PSF.

  Fig.24 (a) is a phase distribution which made reverse direction the turning rotation direction of Fig.21 (a), FIG.24 (b) is a figure of the point-spread function (PSF).

  FIG. 25 (a) is a phase distribution in which the amount of rotation is doubled as compared with the phase distribution in FIG. 21 (a), and FIG. 25 (b) is a diagram of the point spread function (PSF).

  FIG. 26 (a) is an example of a six-row phase distribution without turning. If the distance from the central point is 0 to 1/2 of the effective diameter, it has a rotational symmetry of 1/6 rotation with a plane, a positive phase conversion area and a negative phase conversion area in the periphery, and the phase change amount is It increases in proportion to the distance r from the center point. FIG. 26B is a diagram of the point spread function (PSF).

  Embodiment group 3 is used to introduce concentric phase distribution. "Concentric" means that the same shape is obtained by rotating the angle by an arbitrary amount around the center.

  In the case of using a concentric phase filter, there is a risk that "toroidal concentration" will occur in the combined PSF with the simultaneously used optical system. This "annular concentration" causes two-line blurring.

  FIG. 27 (a) is a concentric phase distribution in which the phase distribution changes sinusoidally as it goes from the center to the radial direction, and FIG. 27 (b) is a diagram of the point spread function (PSF).

  FIG. 28 (a) is a phase distribution obtained by multiplying FIG. 27 (a) by the distance r from the center point, and FIG. 28 (b) is a view of the point spread function (PSF). Fine adjustment of the sine cycle.

  FIG. 29 (a) is a phase distribution of FIG. 27 (a) multiplied by the square of the distance r from the center point, and FIG. 29 (b) is a diagram of the point spread function (PSF). Fine adjustment of the sine cycle.

  FIG. 30 (a) is a phase distribution obtained by multiplying FIG. 27 (a) by the third power of the distance r from the center point, and FIG. 30 (b) is a diagram of the point spread function (PSF). Fine adjustment of the sine cycle.

  FIG. 31 (a) is a phase distribution obtained by multiplying FIG. 27 (a) by the fourth power of the distance r from the center point, and FIG. 31 (b) is a diagram of the point spread function (PSF). Fine adjustment of the sine cycle.

  The comparison of FIGS. 27 to 31 in Embodiment group 3 makes it possible to know the change in PSF shape due to the change in the order of r in the concentric phase distribution. The case of the embodiment group 3 includes the “rotational component”, and it can be understood that the degree of concentration of the PSF in the central portion due to the change of the order of r is larger than that of the comparison form group. The depth of field extension and the order of the phase function are described in US Pat.

  Fig. 32 (a) is a concentric phase distribution in which the phase distribution changes sinusoidally in the radial direction when the distance from the central point is 0 to 1/2 times the effective diameter, and Fig. 32 (b) It is a figure of a point spread function (PSF).

  FIG. 33 (a) is a phase distribution obtained by multiplying FIG. 32 (a) by the distance r from the center point, and FIG. 33 (b) is a diagram of a point spread function (PSF). The fluctuation period has been finely adjusted.

  FIG. 34 (a) is a phase distribution obtained by multiplying FIG. 32 (a) by the square of the distance r from the center point, and FIG. 34 (b) is a diagram of a point spread function (PSF). The fluctuation period has been finely adjusted.

  FIG. 35 (a) is a phase distribution obtained by multiplying FIG. 32 (a) by the third power of the distance r from the center point, and FIG. 35 (b) is a diagram of a point spread function (PSF). The fluctuation period has been finely adjusted.

  FIG. 36 (a) is a phase distribution obtained by multiplying FIG. 32 (a) by the fourth power of the radius r, and FIG. 36 (b) is a diagram of a point spread function (PSF). The fluctuation period has been finely adjusted.

  By comparison of FIGS. 32 to 36 in the embodiment group 3, it is possible to know the change of the PSF shape due to the change of the order of r in the concentric phase distribution having the flat portion at the center. The case of the embodiment group 3 includes the “rotational component”, and it can be understood that the degree of concentration of the PSF in the central portion due to the change of the order of r is larger than that of the comparison form group. The depth of field extension and the order of the phase function are described in US Pat.

  FIG. 37 (a) is a concentric phase distribution in which the phase distribution changes like a cosine as going from the center to the radial direction, and FIG. 37 (b) is a diagram of the point spread function (PSF).

  FIG. 38 (a) is a diagram of a phase distribution whose concentric circle cycle is twice that of the phase distribution of FIG. 37 (a) and its point spread function (PSF).

  FIG. 39 (a) is a diagram of a phase distribution whose concentric circle cycle is three times that of the phase distribution of FIG. 37 (a) and its point spread function (PSF).

  FIG. 40 (a) is a diagram of a phase distribution whose concentric circle period is about 4 times that of the phase distribution of FIG. 37 (a) and its point spread function (PSF).

  FIG. 41 (a) is a diagram of a phase distribution whose concentric circle cycle is eight times that of the phase distribution of FIG. 37 (a) and its point spread function (PSF).

  The comparison of FIG. 37 to FIG. 41 in Embodiment group 3 makes it possible to know the change in PSF shape due to the change in the order of r in the concentric cosine phase distribution. The case of the embodiment group 3 includes the “rotational component”, and it can be understood that the degree of concentration of the PSF in the central portion due to the change of the order of r is larger than that of the comparison form group. The depth of field extension and the order of the phase function are described in US Pat.

[How to change the phase distribution design value]
FIG. 42 is a diagram introducing an example of a method of dividing the phase distribution into ranges of values and modifying the phase distribution. FIG. 42 (a) shows a phase distribution before deformation, and FIG. 42 (b) shows a phase distribution after deformation. The part that changes the phase distribution is 421, and the part that does not change is 422. The phase distribution shape is deformed as shown by 423 by multiplying each part of 421 by a constant coefficient. This method is useful when, for example, the depth of field in the direction closer to the focusing distance of the optical system and the depth of field in the direction farther from the focusing distance of the optical system are separately set. It is a thing. It is preferable to finely adjust the distribution shape so that discontinuities do not occur at the connection between the area 423 after deformation and the area 422 where no change is made.

Chromatic aberration correction principle
FIG. 43 is a diagram for explaining the principle of chromatic aberration correction in the phase filter. In order to correct the chromatic aberration of the phase filter, it is possible to apply a method of combining parts having different apex angles and optical dispersion values of the material, as in the achromatization of the prism and the lens. The apex angle of the main prism is σ ₁ The apex angle of the prism for chromatic aberration correction is σ ₂ and the optical dispersion value of the main prism is ν ₁ The partial dispersion of the v ₁ prism is d n ₁ The apex angle of the prism for chromatic aberration correction is σ ₂ It is desirable that the condition of σ ₁ = δ _ε / dn ₁ (ν ₁ −ν ₂ ) and σ ₂ = δ _ε / dn ₂ (ν ₁ −) ₂ ) be satisfied (Non-Patent Documents 17 and 13) 8 types). In the phase filter, the fluctuation range of the phase fluctuation component is regarded as corresponding to the apex angle of the prism, and is set as the achromatic condition. Further, the number of parts to be combined may be three or more as in the achromatization in the prism and the lens.

  FIG. 44 is a diagram for explaining how a phase filter is bonded. The members having the shapes close to each other in the concave and convex portions corresponding to each other are joined with an adhesive. In order to reduce the mixing of bubbles and the like at the time of bonding, a spiral or radial shape is more effective than a concentric shape. Further, at this time, if the difference in refractive index between adjacent materials is 0.5 or more, the reflectance at the junction boundary becomes too high.

  FIG. 45 is a view showing an example of using the present invention for an eyepiece optical system. An aerial image 451 incident on the eyepiece optical system, a front lens unit 452, a light wavefront conversion element 453, a rear lens unit 454, and an eye point 455 are disposed. If the point spread function (PSF) does not include an unnatural shape such as a straight line according to the present invention, the image with the extended depth of field is used even in the optical system without post processing in FIG. It is possible.

  Figure 46 depicts an application of the present invention to contact lenses, corneal processing, or intraocular lenses. By attaching the contact lens having the phase conversion function of the present invention to the cornea 461, it is possible to extend the depth of field of the eye lens 462. Further, even if the cornea itself is processed to have the phase conversion function of the present invention, it is possible to extend the depth of field of the eyeball lens 462. Furthermore, it is possible to extend the depth of field by giving the phase conversion function of the present invention to the intraocular lens 463. According to the present invention, if the point spread function (PSF) does not include an unnatural shape such as a straight line, an image in which the depth of field is extended is obtained in the usage without post processing in FIG. be able to.

  It is not necessary to form the phase distribution shown in each group of embodiments only on a single optical surface, and it is possible to facilitate component processing by dividing and forming the distribution component into a plurality of optical surfaces. It becomes possible to divert common parts to the optical system.

  The light wavefront conversion element of the present invention is not limited to use only on the refractive surface, and may be used on the reflective surface, the partial transmission surface, and the diffractive surface.

  11: imaging optical system, 12: light wavefront conversion element, 21: aperture central part, 22: aperture peripheral part, 31: light beam passing through aperture peripheral part, 32: light beam passing through aperture central part, 421: phase distribution Part where changes are made, 422: part where no change is made to the phase distribution, 423: a modified phase distribution, 431: a main prism, 432: a prism for correcting chromatic aberration, 451: incident on an eyepiece optical system Aerial image, 452: front lens portion, 453: light wavefront conversion element, 454: rear lens portion, 455: eye point, 461: cornea, 462: eye lens, 463: intraocular lens

Claims (4)

A phase filter for use with an imaging optical system, which is disposed in the vicinity of or in the inside of the imaging optical system, and spatially modulates the phase of the wave front by the imaging optical system, thereby forming the imaging optical system Acts to extend the depth of the image created by the image, and the phase distribution does not include discontinuities, discontinuous boundaries and discontinuities in the phase distribution, and the phase value width of the peripheral area in the effective plane is greater than the phase value width of the central area Largely, there are at least one or more portions for converting the phase in the positive direction and at least one portion for converting the phase in the negative direction in the peripheral region, and a portion for converting the phase in the positive direction in the peripheral region and the phase The amount of phase change in the portion to be converted into a direction has a portion that increases toward the peripheral portion, and includes a helical portion centered on the optical axis in the distribution of the amount of phase conversion in the peripheral portion. A phase filter for use with an imaging optical system, which is disposed in the vicinity of or in the inside of the imaging optical system, and spatially modulates the phase of the wave front by the imaging optical system, thereby forming the imaging optical system Acts to extend the depth of the image created by the image, and the phase distribution does not include discontinuities, discontinuous boundaries and discontinuities in the phase distribution, and the phase value width of the peripheral area in the effective plane is greater than the phase value width of the central area Largely, there are at least one or more portions for converting the phase in the positive direction and at least one portion for converting the phase in the negative direction in the peripheral region, and a portion for converting the phase in the positive direction in the peripheral region and the phase The phase change amount in the portion to be converted into a direction has a portion that increases toward the peripheral portion, and includes a portion that is concentric with the optical axis in the distribution of the phase conversion amount in the peripheral portion. A phase filter for use with an imaging optical system, which is disposed in the vicinity of or in the inside of the imaging optical system, and spatially modulates the phase of the wave front by the imaging optical system, thereby forming the imaging optical system Acts to extend the depth of the image created by the image, and the phase distribution does not include discontinuities, discontinuous boundaries and discontinuities in the phase distribution, and the phase value width of the peripheral area in the effective plane is greater than the phase value width of the central area Largely, there are at least one or more portions for converting the phase in the positive direction and at least one portion for converting the phase in the negative direction in the peripheral region, and a portion for converting the phase in the positive direction in the peripheral region and the phase The amount of phase change in the portion to be converted into a direction has a portion that increases toward the peripheral portion, and the distribution of the amount of phase conversion in the peripheral portion includes a radial shape centered on the optical axis. A phase filter for use with an imaging optical system, which is disposed in the vicinity of or in the inside of the imaging optical system, and spatially modulates the phase of the wave front by the imaging optical system, thereby forming the imaging optical system Acts to extend the depth of the image created by the image, and the phase distribution does not include discontinuities, discontinuous boundaries and discontinuities in the phase distribution, and the phase value width of the peripheral area in the effective plane is greater than the phase value width of the central area Largely, there are at least one or more portions for converting the phase in the positive direction and at least one portion for converting the phase in the negative direction in the peripheral region, and a portion for converting the phase in the positive direction in the peripheral region and the phase The phase change amount in the portion to be converted into the direction has a portion that increases toward the peripheral portion, and the phase distribution shape is substantially rotationally symmetric, and the phase distribution shape is at least one maximum annular zone in the radial direction The Has at least one local minimum annular region, as the phase width of the peripheral region is greater than the phase-value width of the central region.

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