Optical device

Abstract

To provide an optical apparatus capable of sufficiently controlling the clearness of a blurred image even when the iris aperture is greatly changed.SOLUTION: An optical apparatus of the present invention comprises an optical element 103 capable of changing the radius to make a normalized transmittance of 0.25 by 20% or more of the maximum effective radius, an optical system 101 having an iris 102 capable of changing the aperture radius, and a control unit 104 for controlling the transmittance distribution of the optical element 103 and the aperture radius based on control data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical device. [Background technology]

[0002] Conventionally, an image formed by an optical device is required to include blur with a smooth edge in some cases, and blur with a clear edge in other cases. Patent Document 1 discloses an optical device that can smooth or clarify the outline of a blur by providing an optical element that can reversibly switch the distribution of transmittance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-198941 A Summary of the Invention [Problem to be solved by the invention]

[0004] The clarity of the blurred contours must be sufficiently adjustable even when the aperture diameter of the diaphragm is changed significantly. However, the optical device disclosed in Patent Document 1 is insufficient to meet the above demands because it is only possible to sufficiently adjust the clarity of the blurred contours near the maximum aperture. SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an optical device that can sufficiently adjust the clarity of the blurred contour even when the aperture diameter of the diaphragm is changed significantly. [Means for solving the problem]

[0005] The optical device according to the present invention , Tooru excess rate Change the distribution changeable optics children An optical system having a diaphragm with a variable aperture radius and an exit pupil radius of the optical system The first control value specifies and , exit pupil transparent percentage cloth The second control value that specifies Based on 、 Transmission of optical elements Rate distribution and a control unit for controlling the , the normalized transmittance at the position where the normalized radius of the exit pupil is maximum when the radius of the exit pupil is a first value is D a When (1) is set, the control unit sets a first control value that sets the radius of the exit pupil to a first value and a normalized transmittance D a When the second control value having (1) as the second value is input, and the first control value having the radius of the exit pupil as the first value, the normalized transmittance D a When the second control value that sets (1) to a third value different from the second value is input, the transmittance distribution of the optical element is changed in each of the above, and the control unit sets the normalized transmittance at the position where the normalized radius of the exit pupil is maximum when the radius of the exit pupil is the fourth value as D b (1), when the radius of the exit pupil is changed from the first value to the fourth value, 0.75≦D a (1) / D b (1)≦1.25 The transmittance distribution of the optical element is changed so as to satisfy the following condition. It is characterized by the above. Effect of the Invention

[0006] According to the present invention, it is possible to provide an optical device that can sufficiently adjust the clarity of the blurred contour even when the aperture diameter of the diaphragm is changed significantly. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of an imaging apparatus including an optical device according to an embodiment of the present invention. [Diagram 2] A diagram showing the relationship between radius rv025 and the maximum effective radius. [Diagram 3] A graph plotting the distribution of internal normalized transmittance at various values ​​of A and B, or α and β. [Figure 4] Schematic diagram of a distribution variable element having sub-regions. [Diagram 5] FIG. 4 is a schematic cross-sectional view of a distribution variable element having a plurality of colored layers having different transmittance distributions. [Figure 6] 1 is a schematic diagram of a distribution variable element or an aperture of a mechanical diaphragm in a plane perpendicular to the optical axis. [Figure 7] 5 is a flowchart showing an example of control by a control unit in the optical device according to the embodiment. [Figure 8] 5 is a schematic diagram of an exemplary numerical table stored in a storage area in the optical device according to the embodiment. [Figure 9] 6 is a diagram showing an example of a change in distribution of normalized transmittance of the entire system when the exit pupil radius is changed in the optical device according to the embodiment. [Figure 10] 5A and 5B are diagrams illustrating the widths of each light beam in the optical device according to the embodiment. [Figure 11] FIG. 1 is a cross-sectional view of an imaging apparatus including an optical device according to a first and second embodiment when focused on an object at infinity. [Figure 12] FIG. 13 is a cross-sectional view of an imaging apparatus including an optical device according to a third and fourth embodiment when focused on an object at infinity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an optical device according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below may be drawn at a scale different from the actual scale in order to facilitate understanding of the present embodiment.

[0009] In various optical systems, including photographic and video lenses, importance is sometimes attached not only to the characteristics of the imaging surface but also to the image quality of the out-of-focus area, i.e., the quality of the blur. In general, there are cases where a smooth blur with a blurred, melting edge is desired, and cases where a blur with a clear edge is desired.

[0010] As a method for changing the contour of the blur, for example, a method of inserting an apodization filter, the transmittance of which decreases as the distance from the optical axis increases, into the optical system is known. This allows the transmittance distribution of the apodization filter to be superimposed on the blurred image, achieving a smooth blur that appears as if the contours are melting away.

[0011] However, when an apodization filter is inserted, the blurred outline always becomes smooth near the maximum aperture, making it difficult to clarify the blurred outline as desired. Furthermore, when an apodization filter is inserted, the amount of light transmitted through the optical system is reduced, so in shooting scenes where little blurring is desired within the screen, the disadvantages of inserting an apodization filter become greater. Therefore, a method is known in which the apodization effect can be switched on and off by using an optical element that can reversibly control the transmittance distribution, i.e., the clarity of the blurred contour can be adjusted according to need.

[0012] On the other hand, the clarity of the blurred contours must be sufficiently adjustable even when the aperture diameter of the diaphragm is changed significantly, but no optical device that can meet such a requirement is known. SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an optical device that can sufficiently adjust the clarity of the blurred contour even when the aperture diameter of the diaphragm is changed significantly.

[0013] FIG. 1 is a schematic diagram of an imaging device 100 including an optical device according to this embodiment. As shown in FIG. 1, the imaging device 100 includes an imaging optical system 101, a control unit 104, a control value s input unit 106, a control value t input unit 107, a storage area 108, and an imaging surface IP. The imaging optical system 101 includes a mechanical aperture 102 , a variable distribution element 103 , and a lens 105 .

[0014] In addition, images can be recorded on the imaging surface IP by arranging a photoelectric conversion element such as a solid-state imaging element, such as a CMOS (Complementary Metal Oxide Semiconductor) or a CCD (Charge Coupled Device), an organic thin-film imaging element, or a photosensitive film. The optical device according to this embodiment is composed of an imaging optical system 101, a control unit 104, a control value s input unit 106, a control value t input unit 107, and a storage area . The imaging device 100 is composed of the optical device according to this embodiment and an imaging element disposed on an imaging surface IP.

[0015] In the imaging device 100, one lens 105 is disposed on the object side of the mechanical aperture 102 and one on the image side of the variable distribution element 103. However, the present invention is not limited to this, and only one lens may be disposed, or the lens 105 may be disposed between the mechanical aperture 102 and the variable distribution element 103. A curved mirror, a diffractive optical element, or the like may be used in place of the lens 105, and a combination of two or all of the lens, the curved mirror, and the diffractive optical element may be used.

[0016] The imaging optical system 101 may include a plane mirror, and the optical axis OA may be bent by the plane mirror. The imaging optical system 101 and the imaging surface IP may be provided in the same housing, or may be provided in different housings so that they can be separated from each other, such as in an interchangeable lens camera to which an interchangeable lens is attached.

[0017] The optical elements included in the imaging optical system 101 may be separable from one another, or only some of the optical elements included in the imaging optical system 101 may be separable from the imaging plane IP. When the imaging device 100 can be separated into a plurality of parts, the control unit 104 may be included in the part where the imaging optical system 101 is provided, or may be included in the part where the imaging surface IP is provided. The control unit 104 may be separated so that the functions of the control unit 104 are shared between a portion where the imaging optical system 101 is provided and a portion where the imaging surface IP is provided.

[0018] The storage area 108 may be included in the portion where the imaging optical system 101 is provided, or may be included in the portion where the imaging surface IP is provided. An SD card or the like may be used as the storage area 108 and may be removable from the imaging device 100 or replaceable within the imaging device 100 . Moreover, the imaging optical system 101 and the imaging surface IP may be provided in the same housing, and the control unit 104 may be configured to be separable from the housing.

[0019] The control value s input unit 106 and the control value t input unit 107 may be included in the housing in which the imaging optical system 101 is provided, or may be included in the housing in which the imaging surface IP is provided, or may be included separately in different housings. The control value s input unit 106 and the control value t input unit 107 may perform input wirelessly or via a wired input unit or the like included in a housing in which the imaging optical system 101 is provided or a housing in which the imaging surface IP is provided. The control value s input unit 106 and the control value t input unit 107 do not need to be physically distinct parts, but may be configured as the same input unit that can electrically switch between inputting the control value s and inputting the control value t.

[0020] Examples of the control value s input unit 106 and the control value t input unit 107 include a device composed of a ring provided on a lens barrel section that holds the imaging optical system 101 and a device that detects the rotation of the ring, and a device composed of a dial and a device that detects the rotation of the dial. Other examples include a display device with a contact detection function, a button device that detects pressing, a device consisting of a lever and a device that detects the inclination of the lever, and a selector switch device consisting of a knob and a device that detects the rotation of the knob.

[0021] Next, the features of the imaging device 100 will be described. First, the mechanical diaphragm 102 has an aperture radius r within a region through which an effective imaging light beam can pass when the mechanical diaphragm 102 is incorporated in the imaging device 100. sp can be changed. and the aperture radius r sp The maximum and minimum values ​​of r spmax and r spmin In this case, the imaging device 100 has an aperture radius r within the range of the following conditional expression (1). sp It is preferable to use a mechanical aperture 102 that can change the aperture diameter. 0.000≦r spmin / r spmax≦0.500 (1)

[0022] The aperture radius r is set to exceed the upper limit of condition (1). sp If the range in which F can be changed becomes narrower, it becomes difficult to achieve a wide range of F values. In addition, the aperture radius r sp It is not necessary for all values ​​in the range of condition (1) to be continuously available. For example, 0.1r spmax Units or 0.05r spmax Alternatively, the control may be performed so that the value can be taken discretely in units.

[0023] In this way, the aperture radius r sp When controlling discretely, the control unit is preferably finer, at least 0.25r spmax It is preferable to be able to control the F-number with a fineness of 0.1 or less, so that the F-number can be controlled in sufficiently fine steps. In addition, the control unit does not need to be a constant value, and can be set to the aperture radius r sp The control unit may change depending on the value of .

[0024] Furthermore, in the imaging device 100, it is more preferable that the following conditional formulae (1a) to (1d) be satisfied in this order. 0.000≦r spmin / r spmax ≦0.250 (1a) 0.000≦r spmin / r spmax ≦0.100 (1b) 0.000≦r spmin / r spmax ≦0.010 (1c) 0.000≦r spmin / r spmax ≦0.004 (1d)

[0025] The aperture radius r of the mechanical aperture 102 sp is defined as the radius at which the transmittance normalized by the transmittance on the optical axis becomes 0.5 in the mechanical diaphragm 102 in a specified state. When the mechanical diaphragm 102 is made of a light-shielding member having a transmittance of 0.01 or less, the aperture radius r is set to the average value of the distance from the optical axis to the light-shielding member along the circumferential direction. sp Let us assume that. The aperture radius r of the mechanical aperture 102 sp The radius of the exit pupil for the axial light beam of the imaging optical system 101 (hereinafter referred to as the exit pupil radius) is defined as r pa and the exit pupil radius r pa The maximum value of r pamax Let us assume that.

[0026] The mechanical diaphragm 102 may be, for example, an iris diaphragm whose aperture diameter can be changed by moving at least one diaphragm blade, or a Waterhouse diaphragm in which members with different aperture diameters are replaced. When an iris diaphragm is used as the mechanical diaphragm 102, it is preferable that the diaphragm has five or more diaphragm blades. By configuring it in this way, the shape of the bokeh can be kept close to a perfect circle over a wide range of F-numbers.

[0027] A physical aperture capable of controlling the transmittance for each concentric region may be used as the mechanical aperture 102, but in this case, it is preferable that the apodization effect caused by the physical aperture is small. If a large apodization effect is caused by the physical aperture, it becomes difficult to realize a clear blurred outline.

[0028] In the imaging device 100, the distribution variable element 103 is an internal normalized transmittance T v Let r be the radius where v025 Then, the radius r v025 This allows the contour of the blur to be adjusted sufficiently even when the mechanical aperture 102 is narrowed. radius r v025 If the variable range of is narrower than the above, the cases where the blur contour can be freely adjusted will become very rare.

[0029] The above-mentioned maximum effective radius is the distance from the farthest position from the optical axis to the optical axis within the region of the distribution variable element 103 through which the effective imaging light beam can pass, and the radius of the distribution variable element 103 normalized with this distance set to 1 is called the normalized radius r of the distribution variable element 103. v Let us assume that. The effective imaging light flux means a light flux excluding stray light and light rays that form an image outside the area on the imaging surface IP where the image is recorded. Internal normalized transmittance T v means a normalized transmittance normalized by the maximum value in a predetermined transmittance distribution of one distribution variable element 103. Note that, unless otherwise specified, the transmittance at a predetermined radius is defined as the average value of the transmittance at a predetermined radius along the circumferential direction in a plane perpendicular to the optical axis and centered on the optical axis.

[0030] The transmittance may be the average value of the transmittance (visible light transmittance) at wavelengths of 400 nm to 700 nm, 420 nm to 650 nm, or 420 nm to 850 nm, or the representative value at wavelengths of 550 nm or 587.6 nm. In the following, the transmittance is calculated as the representative value at a wavelength of 550 nm. In addition, when the imaging optical system 101 has a plurality of distribution variable elements 103, at least one of the distribution variable elements 103 has a radius r v025 It is sufficient if it is possible to change the effective radius by more than 20%.

[0031] Figure 2 shows the radius r defined above. v025 and the maximum effective radius (r v =1).

[0032] The distribution variable element 103 has a radius r v025 If the variable range is 30% or more of the maximum effective radius, the degree of freedom in adjusting the blurred contour can be increased, and if it is 40% or more of the maximum effective radius, the degree of freedom in adjusting the blurred contour can be increased even more. In addition, when the distribution variable element 103 is configured with a curved surface, the internal normalized transmittance T vThe distribution of can be evaluated by projection onto a plane perpendicular to the optical axis.

[0033] In the imaging device 100, when a transmittance distribution is given to the axial light beam using the distribution variable element 103, in particular, r p Whether .times..times.1 or 0.7, it is preferable to set the transmittance distribution of the exit pupil of the axial light beam so as to satisfy the following conditional expression (2): -6.0≦D'(r p )≦1.0 (2)

[0034] where r p is the exit pupil radius r pa The maximum value r pamax is a normalized radius (hereinafter referred to as normalized exit pupil radius) normalized by and takes a value between 0 and 1. In addition, the normalized transmittance T of the entire system and the normalized exit pupil radius r p The relationship between the function D(r p ), the function D(r p ) normalized exit pupil radius r p Differentiate with respect to D'(r p ) is represented as follows. T = D(r p ) ···(3)

[0035] In addition, the function D(r p )r p =r px The differential D'(r px ) are defined as shown in the following equations (4) and (5). (a) 0≦r px When ≦0.99 D'(r px )=(D(r px +0.01)-D(r px ))×100 (4) (b)r px When >0.99 D'(r px )=(D(r px )-D(r px -0.01)) × 100 (5)

[0036] The normalized transmittance T of the entire system is the transmittance (normalized transmittance) at a predetermined position of the exit pupil for an axial light beam of the imaging optical system 101 normalized by the transmittance on the optical axis.

[0037] If the upper limit of condition (2) is exceeded, it becomes difficult to achieve a transmittance distribution in which the transmittance decreases with increasing distance from the center, and this undesirably causes some parts of the blur to become unnaturally bright or the contours of the blur to be excessively emphasized. On the other hand, if the lower limit of conditional expression (2) is exceeded, the transmittance will no longer change smoothly, making it difficult to make the outline of the blur sufficiently smooth.

[0038] Moreover, it is more preferable that the imaging device 100 satisfy the following conditional formula (2a). -5.0≦D'(r p )≦0.0 (2a)

[0039] In addition, when a transmittance distribution satisfying the following formula (6) is given to the axial light beam by using the distribution variable element 103, , below It is preferable to set the transmittance distribution of the exit pupil for the axial light beam so as to satisfy the following conditional expression (7). D(1)<0.1 (6) -0.80≦ave(D'(r p ))[0.9,1]≦0.00 (7) Here, ave(f(x))[a,b] means the average value of the function f(x) in the interval represented by the following equation (8). a≦x≦b (8)

[0040] If the upper limit of condition (7) is exceeded, the transmittance increases at the edge of the exit pupil, unnaturally accentuating the outline of the blur, which is undesirable. On the other hand, if the lower limit of condition (7) is not reached, the transmittance changes suddenly at the edge of the exit pupil, and the outline of the blur is no longer sufficiently smooth, which is undesirable.

[0041] Moreover, it is more preferable that the imaging device 100 satisfy the following conditional expression (7a). -0.75≦ave(D'(r p ))[0.9,1]≦0.00 (7a)

[0042] Furthermore, in the imaging device 100, it is preferable to set the transmittance distribution of the exit pupil of the axial light beam so as to satisfy the following conditional expression (9). -1.00≦ave(D'(r p ))[0,0.2]≦0.10 (9)

[0043] By satisfying conditional expression (9), it is possible to suppress a decrease in the amount of light caused by the provision of a transmittance distribution. In other words, exceeding the upper limit of condition (9) makes it difficult to achieve a transmittance distribution in which the transmittance decreases with increasing distance from the center, which undesirably causes parts of the blur to appear unnaturally bright or the center of the blur to appear unnaturally dark. On the other hand, if the lower limit of condition (9) is not reached, the decrease in transmittance in an area slightly away from the center becomes large, which undesirably results in a large decrease in the amount of light of the imaging light beam.

[0044] Moreover, it is more preferable that the imaging device 100 satisfy the following conditional expression (9a). -0.70≦ave(D'(r p ))[0,0.2]≦0.10 (9a) It is even more preferable that the imaging device 100 satisfy the following conditional formula (9b). -0.55≦ave(D'(r p ))[0,0.2]≦0.10 (9b)

[0045] In the imaging device 100, the aperture radius r of the mechanical aperture 102 is sp is the maximum value r spmax When the transmittance distribution of the distribution variable element 103 is changed, the maximum transmittance on the optical axis of the exit pupil is set to T max , the value when the distribution variable element 103 has a predetermined transmittance distribution is Tax When the number of variable distribution elements 103 included in the imaging optical system 101 is represented as p, it is preferable that the following conditional expression (10) is always satisfied. 0.3 p <T ax / T max <1.0 ···(10) In other words, in the imaging device 100, the aperture radius r sp is the maximum radius r spmax When the transmittance distribution of the distribution variable element 103 is changed, the maximum and minimum values ​​of the transmittance on the optical axis of the exit pupil are respectively T max and T min When the number of variable distribution elements 103 included in the imaging optical system 101 is represented as p, it is preferable that the following conditional expression (10)′ is satisfied. 0.3 p <T min / T max <1.0 (10)'

[0046] By definition, the upper limit of conditional expression (10) will not be exceeded. On the other hand, falling below the lower limit of conditional expression (10) is not preferable because it increases the change in the amount of light, specifically the decrease in the amount of light, when the transmittance distribution of the distribution variable element 103 is changed.

[0047] Moreover, it is more preferable that the imaging device 100 satisfy the following conditional expression (10a). 0.4 p <T ax / T max <1.0 ···(10a)

[0048] As the transmittance distribution of the distribution variable element 103, for example, a distribution expressed by the following formula (11) can be used.

number

[0049] FIG. 3(a) shows the DV(r v )(=T v ) at various values ​​of A and B.

[0050] Here, consider an imaging optical system 101 that includes only one distribution variable element 103 and one mechanical aperture 102, and in the meridional cross section, the distance d1 in the optical axis direction between the distribution variable element 103 and the center of the most off-axis light beam and the intersection point of the optical axis, and the distance d2 in the optical axis direction between the distribution variable element 103 and the mechanical aperture 102 are both 0. In such an imaging optical system 101, if it is assumed that there is no absorption or reflection of light due to pupil aberration or other elements, and that there is no reflection due to the distribution variable element 103 or the mechanical diaphragm 102, the transmittance distribution formed by the distribution variable element 103 and the mechanical diaphragm 102 and the transmittance distribution of the exit pupil for the axial light beam coincide with each other.

[0051] In the case where the transmittance distributions are the same, for example, the aperture radius r sp is the maximum value r spmax In this case, the coefficients A and B may be set so that the transmittance distribution of the distribution variable element 103 can be changed within the range expressed by the following formula (13) according to the control value v. 1.1≦A≦4.0, 2.0≦B (13)

[0052] In addition, the aperture radius r sp is 0.7r spmax In this case, the coefficients A and B may be set so as to be able to change the transmittance distribution of the distribution variable element 103 within the range expressed by the following formula (14). 1.1≦A≦8.5, 2.0≦B (14) In addition, the aperture radius r spis 0.5r spmax In this case, the coefficients A and B may be set so as to be able to change the transmittance distribution of the distribution variable element 103 within the range expressed by the following formula (15). 1.1≦A≦17.0, 2.0≦B (15)

[0053] In the distribution variable element 103, when a transmittance distribution is given, the transmittance on the optical axis may also decrease. For example, in the distribution variable element 103 whose transmittance distribution is expressed by the formula (11), the ratio T ax / T max is expressed by the following formula (16), a sufficient amount of light can be obtained. T ax / T max =0.5+0.55 / A (16)

[0054] Moreover, as the transmittance distribution of the distribution variable element 103, a distribution expressed by the following formula (17) can be used.

number

[0055] FIG. 3(b) shows the DV(r v )(=T v ) for various values ​​of α and β.

[0056] When the transmittance distribution formed by the distribution variable element 103 and the mechanical diaphragm 102 and the transmittance distribution of the exit pupil for the axial light beam match each other, for example, the aperture radius r sp is the maximum value r spmaxIn this case, the coefficients α and β may be set so that the transmittance distribution of the distribution variable element 103 can be changed within the range expressed by the following equation (19) according to the control value v. 0.30≦α≦0.70, 0≦β≦20 (19) In addition, the aperture radius r sp is 0.7r spmax In this case, the coefficients α and β may be set so as to be able to change the transmittance distribution of the distribution variable element 103 within the range expressed by the following formula (20). 0.26≦α≦0.55, 0≦β≦30 (20)

[0057] For example, in the distribution variable element 103 whose transmittance distribution is expressed by the formula (17), the ratio T ax / T max is expressed by the following formula (21), a sufficient amount of light can be obtained. T ax / T max =0.3+α·exp(-0.1β) ···(21)

[0058] Furthermore, in the distribution variable element 103, it is preferable that even if the transmittance distribution is changed, the values ​​of the spectral transmittance for each wavelength in the wavelength range of 430 nm to 650 nm are approximately the same. Specifically, by making the ratio between the transmittance at two specified wavelengths in the range of 430 nm to 650 nm at a specified point within the effective diameter greater than or equal to 0.75 and less than 1.25, it is possible to suppress coloration in a portion of the blur.

[0059] If the value exceeds the upper limit or falls short of the lower limit, coloring of a part or the whole of the blur becomes noticeable. Furthermore, in the imaging device 100, the above ratio is more preferably equal to or greater than 0.80 and equal to or less than 1.20, and even more preferably equal to or greater than 0.85 and equal to or less than 1.15.

[0060] Moreover, it is preferable that the distribution variable element 103 satisfies the following conditional expression (22), so that the change in color tone of the entire screen can be reduced when the clarity of the blurred contour is changed. (a1-a2) 2 +(b1-b2) 2 <16 ···(22) Here, when the transmittance distribution of the distribution variable element 103 is changed, for two given transmittance distributions, the chromaticities in the L*a*b* space defined by CIE1976 at the imaging position of the axial light beam are (L1, a1, b1) and (L2, a2, b2), respectively.

[0061] Moreover, it is more preferable that the imaging device 100 satisfy the following conditional formula (22a): (a1-a2) 2 +(b1-b2) 2 <8 ···(22a)

[0062] In the imaging device 100, the distribution variable element 103 may be an electrochromic element, a photochromic element, a liquid crystal element, or the like. Electrochromic elements are elements that can reversibly switch between coloring and decoloring by utilizing the electrochromic phenomenon, in which a material becomes colored or decolored as a result of a change in the light transmittance of the material due to a reversible electrochemical reaction that occurs when a voltage is applied.

[0063] A photochromic element is an element that can reversibly switch between coloring and decoloring by utilizing the photochromic phenomenon, in which a substance becomes colored or decolored as a result of a reversible chemical reaction caused by exposure to light, changing the substance's light transmittance. A liquid crystal element is an element that utilizes a liquid crystal material in which the orientation state of the molecules reversibly changes when a voltage is applied, and can switch between transmitting and blocking light by sandwiching a liquid crystal layer between polarizing plates.

[0064] In the above-described element, a desired transmittance distribution can be obtained by dividing the area (effective diameter) through which the effective imaging light beam can pass into small partial areas and driving the areas. FIG. 4 shows a schematic diagram of a device having such sub-regions.

[0065] As shown in Figure 4, an area 400 in the element through which an effective imaging light beam can pass is divided into a number of partial areas 402, and an electrode is provided in each of the partial areas 402, thereby forming an electrode boundary 401 between adjacent partial areas 402. In such an element, the transmittance distribution of the distribution variable element 103 and the aperture radius r of the mechanical diaphragm 102 are adjusted so that the transmittance of the exit pupil for the axial light beam is maximized. sp When the above equation is set, it is preferable that the on-axis light beam passes between the boundaries 401 of the electrodes.

[0066] 4, if the area 400 through which the effective imaging light beam can pass can be divided and driven, the electrode boundary 401 formed in the area 400 may cause the shadow of the boundary 401 to fall on the blur, thereby spoiling the blur. In addition, the control system becomes complicated because it is necessary to drive each of the partial areas 402. For this reason, it is more preferable to use an element in which no electrode boundary 401 is formed within an area 400 through which an effective imaging light beam can pass, that is, an element in which a single electrode is provided in a direction perpendicular to the optical axis.

[0067] Methods for realizing a transmittance distribution without forming electrode boundaries within the region in the element through which the effective imaging light beam can pass include a method of imparting a thickness distribution to the electrodes and a method of utilizing the film resistance of the electrodes. However, when such a method is used, in the case of organic materials that are electrochromic or photochromic and that tend to exhibit little coloration and are easy to suppress, the coloring material is irreversibly altered when a high voltage is applied.

[0068] Therefore, it becomes difficult to variably control the transmittance distribution over a wide range, or when the transmittance distribution is variably controlled over a wide range, the life of the element tends to be significantly shortened. In order to avoid such a disadvantage, it is effective to use an element having a plurality of colored layers.

[0069] FIG. 5 shows a schematic cross-sectional view of an exemplary variable distribution element 103 having multiple colored layers with different transmittance distributions achieved at low voltages. By using a distribution variable element 103 as shown in FIG. 5, it becomes possible to control the transmittance distribution in a wide range.

[0070] 5, a first colored layer 501, a second colored layer 502, and a third colored layer 503 are sandwiched between electrode layers 504, and a voltage is applied via the electrode layers 504. The electrode layers 504 are formed on a substrate 500. Although the distribution variable element 103 shown in FIG. 5 is configured with three colored layers, the number of colored layers and the configuration of the distribution variable element 103 are not limited to this.

[0071] In addition, in the distribution variable element 103 shown in FIG. 5, all the boundary surfaces are formed as flat surfaces, but this is not limiting, and they may be formed as spherical or aspherical surfaces. 5, all the colored layers are formed as an integral unit, but they do not necessarily have to be integral. For example, the colored layers may be disposed separately on the object side and the imaging plane IP side of the mechanical aperture 102.

[0072] In the imaging device 100, a DMD (Digital Mirror Device) may be used as the distribution variable element 103. A DMD is an element that consists of an array of numerous tiny mirrors, and the orientation of each mirror can be controlled individually. This allows each mirror to reflect an incident light beam in a desired direction, making it possible to control whether the mirror transmits or blocks light depending on the incident position of the light beam. Moreover, the distribution variable element 103 may have a refractive power, and may have a function as a diffractive element or a reflective element.

[0073] In order to provide a uniform effect on the outline of the blur, it is preferable that in a coaxial optical system, the transmittance distribution of the distribution variable element 103 and the aperture shape of the mechanical diaphragm 102 have a high degree of rotational symmetry about the optical axis. FIG. 6 shows a schematic diagram of the aperture of the distribution variable element 103 or the mechanical diaphragm 102 in a plane perpendicular to the optical axis.

[0074] Specifically, as shown in Figure 6, the maximum diameter of the area through which the effective imaging light beam can pass is R, and in a given transmittance state or aperture state, the internal normalized transmittance at radius r ∈ [0, R] and angle θ ∈ [0, 2π] (rad) is expressed as g(r, θ). In this case, in the imaging device 100, it is preferable that the transmittance distribution or the aperture shape is set so that the following conditional expression (23) is satisfied for any angles θ1 and θ2. ave(|g(r,θ1)-g(r,θ2)|)[R / 10,R]≦0.3 …(23)

[0075] If the upper limit of condition (23) is exceeded, the shape of the exit pupil of the axial light beam or the outline of the blur on the optical axis will deviate significantly from a circular shape, making the blur unnatural. Moreover, in the imaging device 100, it is more preferable that the following conditional formula (23a) be satisfied: ave(|g(r,θ1)-g(r,θ2)|)[R / 10,R]≦0.15 …(23a) Furthermore, in the imaging apparatus 100, it is even more preferable that the following conditional formula (23b) be satisfied: ave(|g(r,θ1)-g(r,θ2)|)[R / 10,R]≦0.05 …(23b)

[0076] The distribution variable element 103 may include an element having a transmittance distribution that cannot be variably controlled, and the imaging optical system 101 may include an element having a transmittance distribution that cannot be variably controlled.

[0077] FIG. 7A is a flowchart showing an example of control by the control unit 104 in the imaging device 100.

[0078] The control by the control unit 104 includes a process of inputting a control value s (first control value, control information) for specifying the diameter of the exit pupil by the mechanical aperture 102, and a process of inputting a control value t (second control value, control information) for specifying the transmittance distribution of the exit pupil. The control by the control unit 104 includes a step of determining a control value v (a third control value) that specifies the transmittance distribution of the distribution variable element 103 using the control value s and the control value t. That is, in the imaging device 100 , the transmittance distribution of the distribution variable element 103 and the aperture radius of the mechanical diaphragm 102 are controlled based on the radius and transmittance distribution of the exit pupil of the imaging optical system 101 .

[0079] Specifically, as shown in FIG. 7(a), a control value s is input in step S001, and a control value t is input in step S002. Then, in step S003, a control value v is calculated based on the input control values ​​s and t, and in step S004, the control value v is output. The order of steps S001 and S002 may be interchanged.

[0080] Furthermore, the imaging device 100 may be able to directly control the control value v, or may be able to calculate the control value v from only one of the control values ​​s and t. Furthermore, in the imaging device 100, the range of the control value v may be limited by the control value s, the control value t, or the imaging sensitivity, exposure, shutter speed, zoom state, focus state, imaging scene, imaging mode, and the like.

[0081] FIG. 7(b) shows a flowchart for the case where the control unit 104 performs such control. Specifically, a control value s is input in step S011, and a range of a control value v is calculated in step S012 according to the input control value s. Then, in step S013, the range of the control value v is limited, and in step S014, the control value v is input based on the range limited in step S013. Here, the range of the control value v limited in step S013 may be displayed on a display unit (not shown) so as to prompt the input of the control value v in step S014.

[0082] At least one of the control value s and the control value t does not necessarily have to be input by the user, but may be determined by a calculation result in the imaging device 100 and input to the control unit 104. For example, the imaging device 100 may input at least one of the control value s and the control value t based on information such as imaging sensitivity, exposure, shutter speed, zoom state, focus state, shooting scene, and shooting mode. In the above, the range of the control value v is limited in step S013 based on the input control value s, and then the control value v is input in step S014, but this is not limited to the above. For example, the range of the control value t may be limited in step S013 based on the input control value s, and then the control value t may be input in step S014.

[0083] Also, the control value t may be determined so that, for example, a strong transmittance distribution is given when the subject is sufficiently bright, while no or almost no transmittance distribution is given when the subject is dark. Furthermore, F-number information generated by a program AE function, a shutter speed priority AE function, or the like may be used as the control value s. Furthermore, the control value v does not necessarily have to be determined by only the control values ​​s and t, but may be determined based on information such as the imaging sensitivity, exposure, shutter speed, zoom state, and focus state.

[0084] In general, the drive speeds of the mechanical aperture 102 and the distribution variable element 103 are different from each other. Note that the drive speed here is the reciprocal of the time required to drive from a given state to a desired state. At this time, it is preferable that the imaging device 100 be able to drive each of them so that one with a higher drive speed matches the other with a lower drive speed. Moreover, it is preferable that the transmittance distribution of the distribution variable element 103 be able to be changed continuously in a transient process during driving.

[0085] By doing this, the amount of light reaching the imaging surface IP can be changed continuously during the transient process when driving, thereby enabling a smooth transition in the brightness of the image when shooting moving images. At this time, the brightness of the recorded image may be kept constant in combination with an automatic exposure program.

[0086] Furthermore, even when capturing still images, for example, in cases where the imaging device 100 has a display device that allows the moving image recorded on the imaging surface IP to be checked in real time, it is possible to prevent the brightness of the moving image displayed on the display device from changing suddenly.

[0087] The imaging device 100 can use various control methods as described above, and a combination of two or all of such methods may be used, or a combination of two or all of the control methods may be used by switching between them.

[0088] As described above, the control unit 104 receives the control value s and the control value t as input signals from the control value s input unit 106 and the control value t input unit 107, respectively, and outputs the control value v corresponding to the control values ​​s and t. Here, a method for determining the corresponding control value v may be, for example, to provide a memory area 108 in the imaging device 100, store the control values ​​v for each combination of control values ​​s and t in advance as a numerical table in the memory area 108, and refer to the numerical table in response to an input of a control value.

[0089] FIG. 8 shows a schematic diagram of an exemplary value table held in the memory area 108. FIG. 8 shows how, for example, for a combination of control values ​​s1 and t1, the corresponding control value v1 is referenced, and for a combination of control values ​​s2 and t2, the corresponding control value v2 is referenced.

[0090] Moreover, the control value v may be calculated by expressing the control value v as a function of the control values ​​s and t. For example, for integers i and j greater than or equal to 0, integer constant n greater than or equal to i, and integer constant m greater than or equal to j, for any i and j, the constant a ij is stored in advance as a value in storage area 108, and the control value v can be calculated by a function such as that shown in the following equation (24).

number

[0091] Here, by increasing n and m in the polynomial function shown in equation (24) to increase the number of terms on the right-hand side, the control value v can be calculated more accurately. Furthermore, the control value v does not necessarily have to be a scalar, but may be in the form of a vector or matrix including multiple values.

[0092] Furthermore, the control value v is used to determine the transmittance distribution of the distribution variable element 103, but may be used for other purposes. For example, the control value v can be used to control the exposure, the sensitivity of the solid-state image sensor, the F-number, the shutter speed, the autofocus, the white balance, and the like.

[0093] Figure 9 shows an example of how the transmittance of the axial light beam on the exit pupil, that is, the distribution of the normalized transmittance T of the entire system, changes when the F-number, i.e., the exit pupil diameter, is changed while keeping the smoothness of the blurred contour constant. More specifically, FIG. 9 shows the F-number when the mechanical aperture 102 is fully opened. max Then, F max <F a <F b F value F a and F b For F, max , F a , F b 4 shows an example of controlling the transmittance distribution of the exit pupil when the transmittance is changed as follows:

[0094] In FIG. 9, curves 301, 302, and 303 are respectively F values. max , F a and F b The graph shows the distribution of the normalized transmittance T of the entire system when At this time, the aperture radius r of the mechanical diaphragm 102 is set so that the exit pupil diameter corresponds to the desired F value. sp is changed, and the transmittance distribution of the distribution variable element 103 is changed accordingly. This makes it possible to change the magnitude of blur while keeping the normalized transmittance D(1) at the outermost periphery of the exit pupil, that is, the magnitude of the blur smoothing effect, constant.

[0095] It is not necessary to make the transmittance at the outermost periphery of the exit pupil constant. For example, p Alternatively, the transmittance may be controlled to be constant at positions where the transmittance is 0.95, 0.90, 0.85, or 0.80. Alternatively, the transmittance at the plurality of positions may be controlled by referring to the normalized exit pupil radius r p Alternatively, the transmittance may be controlled so that the average of the transmittance at the position of 0.95 and the transmittance at the position of 0.80 is kept constant. Or, the normalized exit pupil radius r p Alternatively, the transmittance may be controlled so that the square root of the sum of the squares of the transmittance at the position of 0.90 and the transmittance at the position of 0.85 is constant.

[0096] In addition, it is not necessary to keep the transmittance constant. In this case, for example, D(1) is used as the reference, and D(1) before changing the F value is used as D a (1) and D(1) after changing the F value. b When (1) is set, it is preferable that the following condition (25) be satisfied: 0.75≦D a (1) / D b (1)≦1.25 (25) If the upper limit of condition (25) is exceeded, the blurred contours become smoother as the F-number changes. On the other hand, if the lower limit of condition (25) is exceeded, the blurred contours become clearer as the F-number changes.

[0097] In the imaging device 100, the maximum value of the transmittance at the position where the marginal ray of the axial light beam of the distribution variable element 103 passes and the value when the distribution variable element 103 has a predetermined transmittance distribution are respectively T m and T c (v,r pa ) then the exit pupil radius r pa is pamax and 0.7r pamax In either case, it is preferable that the following condition (26) be satisfied: 0.002≦T c (v,r pa ) / T m ≦0.500 (26)

[0098] If the upper limit of condition (26) is exceeded, the exit pupil radius r pa In a wide range, it becomes difficult to smooth out the blurred contours. On the other hand, if the lower limit of condition (26) is exceeded, the exit pupil radius r pa In a wide range, it becomes difficult to clearly define the outline of the blur.

[0099] In the imaging device 100, the exit pupil radius r pa is 0.6r pamax It is more preferable that condition (26) be satisfied even in this case. In that case, the exit pupil radius r pa The blur contour can be smoothed over a wider range.

[0100] Moreover, in the imaging apparatus 100, it is more preferable that the following conditional formula (26a) be satisfied: 0.002≦T c (v,r pa ) / T m ≦0.350 (26a) Furthermore, in the imaging apparatus 100, it is even more preferable that the following conditional formula (26b) be satisfied: 0.002≦T c (v,r pa ) / T m ≦0.250 (26b)

[0101] When the total optical length of image pickup apparatus 100 is L, it is preferable that the position at which distribution variable element 103 is disposed in image pickup apparatus 100 satisfies the following conditional expression (27). 0.00≦d1 / L≦0.35 (27) The total optical length here is defined as the distance from the surface closest to the object in the imaging optical system 101 to the image plane.

[0102] If the upper limit value of conditional expression (27) is exceeded, particularly when the mechanical aperture 102 is fully opened, the effects of the distribution variable element 103 on the blurring of the upper and lower lines of the off-axis light beam will differ from each other, resulting in uneven contours of the blurring. By definition, the lower limit of condition (27) is not exceeded.

[0103] Furthermore, in the case where the distribution variable element 103 has a portion that forms the transmittance distribution and a portion that contributes very little to the transmittance distribution, such as the substrate or driving mechanism, the position of the portion that forms the transmittance distribution is determined as the position of the distribution variable element 103. In addition, when the distribution variable element 103 or the portion that forms the transmittance distribution has a thickness in the optical axis direction, the center position in the optical axis direction is taken as the position of the distribution variable element 103 .

[0104] Furthermore, in the imaging device 100, it is more preferable that the following conditional expressions (27a) to (27d) be satisfied in this order. 0.00≦d1 / L≦0.30 (27a) 0.00≦d1 / L≦0.26 (27b) 0.00≦d1 / L≦0.20 (27c) 0.00≦d1 / L≦0.10 (27d)

[0105] Furthermore, in the image pickup apparatus 100, if conditional expression (27) is satisfied in one shooting state, a minimum effect can be obtained. However, when the optical path of the most off-axis light beam changes significantly due to zooming, focusing, or the like, it is particularly preferable to move the distribution variable element 103 in the optical axis direction along with zooming or focusing so that conditional expression (27) is satisfied.

[0106] In the imaging device 100, it is preferable that the position at which the distribution variable element 103 is disposed satisfies the following conditional expression (28). 0.00≦d2 / L≦0.35 (28)

[0107] If the upper limit of condition (28) is exceeded, when the mechanical aperture 102 is narrowed, the effect of the distribution variable element 103 on the blurring of the upper and lower lines of the off-axis light beam will differ from each other, resulting in a non-uniform outline of the blurring. By definition, the lower limit of condition (28) is not exceeded.

[0108] Furthermore, in the imaging device 100, it is more preferable that the following conditional formulae (28a) through (28c) be satisfied in this order. 0.00≦d2 / L≦0.30 (28a) 0.00≦d2 / L≦0.25 (28b) 0.00≦d2 / L≦0.10 (28c) In this case, the uniformity of the outline of the blur can be improved over a wider range of the exit pupil diameter defined by the mechanical diaphragm 102.

[0109] In the imaging device 100, the aperture radius r of the mechanical aperture 102 sp The maximum value r spmax Then, the widths of the most off-axis light beam and the on-axis light beam that form an image on the imaging plane IP in the meridional section when they enter the imaging optical system 101 are respectively expressed as w 10 and w0, it is preferable that the following conditional expression (29) be satisfied: 0.7≦w 10 / w0≦1.3 (29)

[0110] If the upper limit value of conditional expression (29) is exceeded or the lower limit value is exceeded, the difference between the beam widths of the on-axis light beam and the off-axis light beam becomes large, and the action of the variable distribution element 103 on each beam becomes non-uniform within the screen. Moreover, in the imaging apparatus 100, it is more preferable that the following conditional formula (29a) be satisfied: 0.75≦w 10 / w0≦1.20 (29a) Furthermore, in the imaging apparatus 100, it is even more preferable that the following conditional formula (29b) be satisfied: 0.9≦w 10 / w0≦1.1 (29b)

[0111] Aperture radius r of mechanical aperture 102 sp The maximum value r spmax When the light beam width in the direction perpendicular to the optical axis of the axial light beam on the distribution variable element 103 in the meridional section is w b0 The width of the portion where the most off-axis light beam and the on-axis light beam overlap each other on the distribution variable element 103 in the direction perpendicular to the optical axis is w lap Let us assume that. At this time, it is preferable that the imaging device 100 satisfies the following conditional expression (30). 0.6≦(w lap / w b0 ) / (w 10 / w0)≦1.3 (30) FIG. 10 shows the width w 10 , w0, w b0 and wlap is shown diagrammatically.

[0112] If the lower limit of condition (30) is exceeded, the transmittance of off-axis light beams is significantly reduced by the distribution variable element 103, resulting in a significant reduction in the amount of peripheral light. On the other hand, if the upper limit of condition (30) is exceeded, the difference between the beam widths of the on-axis light beam and the off-axis light beam becomes large, and the effect of the variable distribution element 103 on each beam becomes non-uniform within the screen.

[0113] Moreover, in the imaging device 100, it is more preferable that the following conditional formula (30a) be satisfied: 0.7≦(w lap / w b0 ) / (w 10 / w0)≦1.2 (30a)

[0114] In the imaging device 100, a plurality of variable distribution elements 103 may be provided in the imaging optical system 101. Furthermore, when a plurality of variable distribution elements 103 are provided, the transmittance distributions of the respective variable distribution elements 103 may be the same as or different from each other. By arranging the distribution variable element 103 at an appropriate position, it is possible to improve the uniformity of the smoothness of the blurred contour of the off-axis light beam. Additionally, in the imaging device 100, the imaging optical system 101 may be provided with a plurality of mechanical apertures 102.

[0115] Furthermore, the imaging device 100 is not limited to a general camera, but may be a pair of binoculars, a monocular, a microscope, or the like.

[0116] Next, examples of the optical device according to this embodiment will be specifically described. In each of the following examples, the refractive index and Abbe number of the distribution variable element 103 are 1.5163 and 64.14, respectively, and are homogeneous; however, they do not necessarily have to have these values, and they do not necessarily have to be homogeneous. Further, the transmittance distribution of the exit pupil is calculated on the assumption that the transmittance distribution is formed at the center position of the distribution variable element 103 in the optical axis direction.

[0117] [Example 1] FIG. 11A is a cross-sectional view of an image capturing apparatus 100a including the optical device according to the first embodiment when focused on an object at infinity. The imaging device 100a has the same configuration as the embodiment shown in FIG. 1, except for the imaging optical system 101a.

[0118] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The imaging optical system of each embodiment is configured to have multiple lens groups. In this specification, a lens group is a group of lenses that move or stand still as a unit during focusing. That is, in the imaging optical system of each embodiment, the distance between adjacent lens groups changes during focusing from infinity to a close distance. Note that the lens group may be composed of one lens or multiple lenses.

[0119] As shown in FIG. 11(a), an imaging optical system 101a has a mechanical aperture 102a and a variable distribution element 103a. The mechanical diaphragm 102a and the distribution variable element 103a operate by receiving an input signal from a control unit (not shown). In addition, in FIG. 11(a), an on-axis light beam 110a and an extreme off-axis light beam 111a are also shown.

[0120] The imaging optical system 101a has a three-group configuration consisting of, in order from the object side to the image side, a first lens group 120a having positive refractive power, a second lens group 121a having negative refractive power, and a third lens group 122a having positive refractive power. In the imaging optical system 101a, the 9th surface is the mechanical aperture 102a, and the 10th and 11th surfaces are the entrance surface and exit surface of the distribution variable element 103a, respectively, so that the distribution variable element 103a is disposed adjacent to the image side of the mechanical aperture 102a. Moreover, in the imaging device 100a, focusing is performed by moving the second lens group 121a having negative refractive power toward the image side.

[0121] In the imaging device 100a, the transmittance distribution of the variable distribution element 103a is assumed to be expressed by equation (11). Then, the mechanical aperture 102a is opened, that is, the aperture radius is r sp The maximum value r spmax The distribution of the total system normalized transmittance T in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients A and B when

[0122] [Table 1]

[0123] [Table 2]

[0124] As the most off-axis light beam 111a is asymmetric between the upper line side and the lower line side, the positions of the upper line, lower line and principal ray of the most off-axis light beam 111a are set to -1, 1 and 0, respectively, and normalized on the upper line side and lower line side, respectively. The transmittance is also standardized by the maximum transmittance of the most off-axis light beam.

[0125] The above-mentioned distribution of the normalized transmittance T of the entire system is handled in the same manner in the following Examples 2 to 4.

[0126] In addition, the aperture radius r of the mechanical aperture 102a sp A 0.7r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients A and B when

[0127] [Table 3]

[0128] [Table 4]

[0129] In addition, the aperture radius r of the mechanical aperture 102a sp 0.5r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients A and B when

[0130] [Table 5]

[0131] [Table 6]

[0132] It should be noted that the values ​​of the coefficients A and B shown in Tables 1 to 6 are merely examples, and are not limited to these, and the coefficients A and B can take various values ​​in the imaging device 100a.

[0133] Furthermore, as shown in Tables 1, 3 and 5, for the exit pupil of the axial light beam, the transmittance D(1) at the effective diameter end is approximately equal to one another in, for example, the following three states (a) to (c). (a)r sp =r spmax , A=1.1, B=2.4 (b)r sp =0.7r spmax , A=2, B=2 (c)r sp =0.5r spmax , A=4, B=2

[0134] Therefore, when changing the size of the blur while maintaining the transmittance D(1) at the effective diameter end, i.e., the smoothness of the blur contour, constant, the control value v can be determined so as to obtain a transmittance distribution corresponding to A and B as shown in (a) to (c) in response to the change in the control value s that defines the size of the blur.

[0135] [Example 2] FIG. 11B is a cross-sectional view of an imaging device 100b including the optical device according to the second embodiment when focused on an object at infinity.

[0136] As shown in FIG. 11(b), the imaging optical system 101b has a mechanical aperture 102b and a variable distribution element 103b. The mechanical aperture 102b and the distribution variable element 103b operate by receiving an input signal from a control unit (not shown). In addition, in FIG. 11(b), an on-axis light beam 110b and an extreme off-axis light beam 111b are also shown.

[0137] The imaging optical system 101b has a two-group configuration including, in order from the object side to the image side, a first lens group 120b having positive refractive power and a second lens group 121b having negative refractive power. In the imaging optical system 101b, the mechanical diaphragm 102b and the variable distribution element 103b are arranged so that the thirteenth surface is the mechanical diaphragm 102b, and the seventh and eighth surfaces are the entrance surface and exit surface of the variable distribution element 103b, respectively. Moreover, in the imaging device 100b, focusing is performed by moving the second lens group 121b having negative refractive power toward the image side.

[0138] In the imaging device 100b, the transmittance distribution of the variable distribution element 103b is assumed to be expressed by equation (17). Then, the mechanical aperture 102b is opened, that is, the aperture radius is r sp The maximum value r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients α and β when

[0139] [Table 7]

[0140] [Table 8]

[0141] In addition, the aperture radius r of the mechanical aperture 102b sp A 0.7r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients α and β when

[0142] [Table 9]

[0143] [Table 10]

[0144] It should be noted that the values ​​of the coefficients α and β shown in Tables 7 to 10 are merely examples, and are not limited to these, and the coefficients α and β can take various values ​​in the image pickup device 100b.

[0145] [Example 3] FIG. 12A is a cross-sectional view of an imaging device 100c including an optical device according to the third embodiment when focused on an object at infinity.

[0146] As shown in FIG. 12(a), an imaging optical system 101c includes a mechanical aperture 102c and a variable distribution element 103c. The mechanical aperture 102c and the distribution variable element 103c operate by receiving an input signal from a control unit (not shown). In addition, in FIG. 12(a), an on-axis light beam 110c and an extreme off-axis light beam 111c are also shown.

[0147] The imaging optical system 101c has a two-group configuration including, in order from the object side to the image side, a first lens group 120c having positive refractive power and a second lens group 121c having negative refractive power. In the imaging optical system 101c, the mechanical diaphragm 102c and the variable distribution element 103c are arranged so that the sixth surface is the mechanical diaphragm 102c, and the first and second surfaces are the entrance surface and exit surface of the variable distribution element 103c, respectively. Moreover, in the imaging device 100c, focusing is performed by moving the first lens group 120c having positive refractive power toward the object side.

[0148] In the imaging device 100c, the transmittance distribution of the variable distribution element 103c is assumed to be expressed by equation (11). Then, the mechanical aperture 102c is opened, that is, the aperture radius r sp The maximum value r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients A and B when

[0149] [Table 11]

[0150] [Table 12]

[0151] In addition, the aperture radius r of the mechanical aperture 102c sp A 0.7r spmax The distribution of the total system normalized transmittance T in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients A and B when

[0152] [Table 13]

[0153] [Table 14]

[0154] It should be noted that the values ​​of the coefficients A and B shown in Tables 11 to 14 are merely examples, and are not limited to these, and the coefficients A and B can take various values ​​in the imaging device 100c.

[0155] [Example 4] FIG. 12B is a cross-sectional view of an image capturing apparatus 100d including an optical device according to the fourth embodiment when the image capturing apparatus 100d is focused on an object at infinity.

[0156] As shown in FIG. 12(b), the imaging optical system 101d has a mechanical aperture 102d, a first distribution variable element 1031d, and a second distribution variable element 1032d. The mechanical aperture 102d, the first distribution variable element 1031d, and the second distribution variable element 1032d operate by receiving input signals from a control unit (not shown). In addition, in FIG. 12(b), an on-axis light beam 110d and an off-axis light beam 111d are also shown.

[0157] The imaging optical system 101d has a two-group configuration including, in order from the object side to the image side, a first lens group 120d having positive refractive power and a second lens group 121d having negative refractive power. In the imaging optical system 101d, the mechanical aperture 102d is arranged so that the fifth surface is the mechanical aperture 102d, the second and third surfaces are the entrance surface and exit surface, respectively, of the first distribution variable element 1031d, and the seventh and eighth surfaces are the entrance surface and exit surface, respectively, of the second distribution variable element 1032d, i.e., between the first distribution variable element 1031d and the second distribution variable element 1032d. Furthermore, in the image pickup device 100d, focusing is performed by moving the first lens group 120d having positive refractive power toward the object side.

[0158] In the imaging device 100d, the transmittance distribution of each of the first distribution variable element 1031d and the second distribution variable element 1032d is assumed to be expressed by equation (17). Then, the mechanical aperture 102d is opened, that is, the aperture radius is r sp The maximum value r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients α and β when

[0159] [Table 15]

[0160] [Table 16]

[0161] In addition, the aperture radius r of the mechanical aperture 102d sp 0.7r spmax The distribution of the normalized transmittance T of the entire system in the meridional section for the on-axis light beam and the most off-axis light beam for various coefficients α and β when

[0162] [Table 17]

[0163] [Table 18]

[0164] It should be noted that the values ​​of the coefficients α and β listed in Tables 15 to 18 are merely examples, and are not limited to these, and the coefficients α and β can take various values ​​in the image capture device 100d.

[0165] Next, Numerical Examples 1 to 4 corresponding to the above-mentioned Examples 1 to 4, respectively, will be described. In each numerical example, i is a surface number indicating the ith surface from the object side, and ri is the radius of curvature (mm) of the ith surface from the object side. Furthermore, di is the surface separation (mm) on the optical axis between the i-th surface and the (i+1)-th surface from the object side, and ndi and νdi are the refractive index and Abbe number, respectively, of the optical member between the i-th surface and the (i+1)-th surface. The Abbe number νd is expressed as follows, where Nd, NF, and NC are the refractive indices at the d line (587.6 nm), F line (486.1 nm), and C line (656.3 nm) of the Fraunhofer lines: νd=(Nd-1) / (NF-NC) It is expressed as:

[0166] The focal length f, F-number Fno, and angle of view 2ω (degrees) shown in each numerical example are values ​​when the focus is on an object at infinity. Also, BF is the back focus, which is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image surface, expressed as the air-equivalent length. The total lens length indicates the distance from the first surface to the image surface, and aspherical surfaces are indicated by the symbol "*" after the surface number.

[0167] The aspheric shape is expressed by the following equation (31), where X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is a conic constant, and A4 and A6 are aspheric coefficients.

[0168]

number

[0169] In addition, in each numerical example, "e±Z" is "10 ±Z " and the effective diameter of the aperture surface is the aperture radius r sp The maximum value of r spmax is equivalent to.

[0170] [Numerical Example 1] Unit: mm Surface Data Surface number ri di ndi νdi Effective diameter 1 62.721 21.86 1.43875 94.9 83.10 2 -312.309 0.38 80.57 3 55.455 9.69 1.63858 55.2 63.34 4 258.552 2.14 61.21 5 -1445.156 3.35 1.90525 35.0 61.20 6 101.890 2.30 54.38 7 39.791 4.79 1.80518 25.4 46.35 8 30.612 9.46 39.87 9(Aperture) ∞ 1.50 37.52 10 ∞ 3.00 1.51633 64.1 36.60 11 ∞ 0.15 35.68 12 60.423 2.54 1.72916 54.7 35.94 13 230.996 (variable) 35.85 14 -1069.370 3.07 2.10420 17.0 35.61 15 -89.758 1.72 1.74950 35.0 35.49 16 36.341 (variable) 34.10 17 -33.975 1.60 1.64769 33.8 42.58 18 93.253 16.29 1.72916 54.7 54.61 19 -49.183 0.19 57.10 20 87.234 10.61 1.74100 52.6 63.62 21 -214.304 (variable) 63.39 Image plane ∞ Various data Focal length 133.05 F-number 2.06 Angle of view: 9.24 Image height 21.64 Lens length 170.39 BF 45.96 d13 1.99 d16 27.80 d21 45.96 Entrance pupil position 70.15 Exit pupil position -256.09 Front principal point position 144.60 Back principal point position -87.09 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 83.08 61.16 10.00 -40.07 2 14 -56.59 4.79 2.52 0.08 3 17 74.18 28.69 22.00 9.75 Single lens data Lens starting surface focal length 1 1 121.20 2 3 108.53 3 5 -105.03 4 7 -214.74 5 10 0.00 6 12 111.52 7 14 88.59 8 15 -34.31 9 17 -38.26 10 18 46.40 11 20 84.94

[0171] [Numerical Example 2] Unit: mm Surface Data Surface number ri di ndi νdi Effective diameter 1 142.039 16.50 1.43875 94.9 99.96 2 -291.943 0.10 99.24 3 113.394 12.00 1.43875 94.9 92.23 4 2251.000 3.50 90.60 5 -493.629 3.00 1.78800 47.4 89.70 6 188.579 22.00 85.89 7 ∞ 3.00 1.51633 64.1 80.54 8 7704.935 38.00 79.91 9 74.095 11.20 1.45650 90.3 65.86 10 574.708 2.00 63.62 11 47.590 2.60 1.75501 51.2 56.26 12 40.574 32.80 52.98 13 (Aperture) ∞ (Variable) 39.97 14 212.437 4.00 1.78880 28.4 38.90 15 -155.217 1.60 1.75501 51.2 38.14 16 60.802 (variable) 35.91 Image plane ∞ Various data Focal length 399.84 F-number 4.00 Angle of view: 3.10 Image height 21.64 Lens length 298.46 BF 145.16 d13 1.00 d16 145.16 Entrance pupil position 313.91 Exit pupil position -3.95 Front principal point position -358.41 Back principal point position -254.68 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 181.84 146.70 30.02 -110.84 2 14 -119.89 5.60 4.63 1.42 Single lens data Lens starting surface focal length 1 1 220.33 2 3 271.69 3 5 -172.83 4 7 -14922.50 5 9 185.04 6 11 -433.68 7 14 114.25 8 15 -57.68

[0172] [Numerical Example 3] Unit: mm Surface Data Surface number ri di ndi νdi Effective diameter 1 ∞ 2.00 1.51633 64.1 31.03 2∞1.25 29.93 3 29.889 7.50 1.88300 40.8 26.16 4 -374.377 2.00 1.67270 32.2 22.17 5 36.994 5.25 18.54 6(Aperture) ∞ 4.00 15.31 7 -30.069 0.90 1.69895 30.1 14.35 8 18.311 3.60 1.88300 40.8 17.11 9 190.435 1.50 17.99 10 47.549 5.60 1.77250 49.5 20.95 11* -43.197 (variable) 22.11 12 -76.796 2.00 1.58144 40.9 23.53 13 -110.979 10.70 24.27 14 -15.782 1.00 1.53172 48.8 26.05 15 -229.999 0.15 33.89 16 -2585.005 5.90 1.91082 35.3 35.23 17 -35.964 (variable) 36.09 Image plane ∞ Aspheric Data Page 11 K = 0.00000e+000 A 4= 1.31849e-005 A 6=-7.72465e-010 Various data Focal length 49.00 F-number 2.50 Angle of view: 23.82 Image height 21.64 Lens length 68.15 BF 11.00 d11 3.80 d17 11.00 Entrance pupil position 16.74 Exit pupil position -38.01 Front principal point position 16.75 Back principal point position -38.00 Lens Group Data Group Starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 39.81 33.60 18.05 -13.67 2 12 -186.10 19.75 -12.55 -31.94 Single lens data Lens starting surface focal length 1 1 0.00 2 3 31.62 3 4 -49.95 4 7 -16.16 5 8 22.72 6 10 30.11 7 12 -438.23 8 14 -31.92 9 16 40.00

[0173] [Numerical Example 4] Unit: mm Surface Data Surface number ri di ndi νdi Effective diameter 1 29.889 7.50 1.88300 40.8 26.49 2 -374.377 0.30 1.51633 64.1 22.53 3 -374.377 2.00 1.67270 32.2 22.15 4 36.994 5.25 18.49 5(Aperture) ∞ 4.00 15.12 6 -30.069 0.90 1.69895 30.1 14.15 7 18.311 0.30 1.51633 64.1 17.02 8 18.311 3.60 1.88300 40.8 17.50 9 190.435 1.50 18.31 10 47.549 5.60 1.77250 49.5 21.29 11* -43.197 (variable) 22.39 12 -76.796 2.00 1.58144 40.9 23.75 13 -110.979 10.70 24.47 14 -15.782 1.00 1.53172 48.8 26.16 15 -229.999 0.15 34.06 16 -2585.005 5.90 1.91082 35.3 35.40 17 -35.964 (variable) 36.23 Image plane ∞ Aspheric Data Page 11 K = 0.00000e+000 A 4= 1.31849e-005 A 6=-7.72465e-010 Various data Focal length 48.82 F-number 2.50 Angle of view: 23.90 Image height 21.64 Lens length 65.03 BF 10.53 d11 3.80 d17 10.53 Entrance pupil position 14.58 Exit pupil position -38.44 Front principal point position 14.73 Back principal point position -38.30 Lens Group Data Group starting plane Focal length Lens length Front principal point position Rear principal point position 1 1 39.75 30.95 16.09 -13.93 2 12 -186.10 19.75 -12.55 -31.94 Single lens data Lens starting surface focal length 1 1 31.62 2 2 2657272.46 3 3 -49.95 4 6 -16.16 5 7 6356.87 6 8 22.72 7 10 30.11 8 12 -438.23 9 14 -31.92 10 16 40.00

[0174] Moreover, the numerical values ​​corresponding to the conditional expressions (27) to (30) for each numerical embodiment are shown in the following Table 19. Note that the numerical values ​​shown in Table 19 are all values ​​when focused on an object at infinity.

[0175] [Table 19]

[0176] In addition, in the fourth numerical example, numerical values ​​corresponding to the conditional expressions (27) to (30) for the second distribution variable element 1032d are shown. When two or more distribution variable elements are provided as in Numerical Example 4, it is sufficient that at least one of the distribution variable elements satisfies the conditional expressions (27) to (30). In the fourth numerical embodiment, the first distribution variable element 1031d also satisfies the conditional expressions (27) to (30).

[0177] Furthermore, the transmittance distributions and imaging optical systems shown in each of the first to fourth embodiments are not limited to the above combinations. For example, in the first embodiment, a variable distribution element having a transmittance distribution expressed by formula (17) may be used in place of the variable distribution element having a transmittance distribution expressed by formula (11). In the second embodiment, a variable distribution element having a transmittance distribution expressed by equation (17) may be used instead of a variable distribution element having a transmittance distribution expressed by equation (11). In the fourth embodiment, instead of one of the two distribution variable elements having the transmittance distribution expressed by the formula (17), a distribution variable element having the transmittance distribution expressed by the formula (11) may be used.

[0178] In addition, a distribution variable element that realizes a transmittance distribution different from the transmittance distribution expressed by equation (11) or equation (17) may be used, an imaging optical system having a retrofocus type configuration may be used, or a zoom lens or a macro lens may be used as the imaging optical system.

[0179] Although the preferred embodiments have been described above, the present invention is not limited to these embodiments, and various modifications and variations are possible within the scope of the gist thereof. [Explanation of symbols]

[0180] 101 Imaging optical system (optical system) 102 Mechanical aperture (aperture) 103 Distribution variable element (optical element) 104 Control section

Claims

1. An optical system having an optical element capable of changing a transmittance distribution and an aperture having a changeable aperture radius; a control unit that controls a transmittance distribution of the optical element based on a first control value that specifies a radius of an exit pupil of the optical system and a second control value that specifies a transmittance distribution of the exit pupil, When the radius of the exit pupil is a first value, the normalized transmittance at a position where the normalized radius of the exit pupil is maximum is denoted by D a (1), the control unit changes the transmittance distribution of the optical element when the first control value that sets the radius of the exit pupil to the first value and the second control value that sets the normalized transmittance D a (1) to a second value are input, and when the first control value that sets the radius of the exit pupil to the first value and the second control value that sets the normalized transmittance D a (1) to a third value different from the second value are input, When a normalized transmittance at a position where the normalized radius of the exit pupil is maximum when the radius of the exit pupil is a fourth value is defined as D b (1), when the radius of the exit pupil is changed from the first value to the fourth value, 0.75≦D a (1) / D b (1)≦1.25 2. An optical device comprising: an optical element having a transmittance distribution that is changed so as to satisfy the following condition:

2. The optical device as described in claim 1, characterized in that the radius at which the optical element has a normalized transmittance of 0.25 can be changed by more than 20% of the maximum effective radius.

3. 3. The optical device according to claim 1, wherein the control unit determines a third control value that specifies the transmittance distribution of the optical element based on the first control value and the second control value.

4. 4. The optical device according to claim 3, wherein the control unit limits the range of the second or third control value based on the first control value.

5. The optical device according to claim 4 , further comprising a display unit that displays the limited range.

6. The maximum value of the transmittance at the position where the marginal ray of the axial light beam passes through the optical element and the value when the optical element has a predetermined transmittance distribution are denoted by T ｍ and T ｃ , the maximum value of the radius of the exit pupil of the optical system is r ｐａｍａｘ Then, the radius of the exit pupil of the optical system is r ｐａｍａｘ and 0.7r ｐａｍａｘ At any time 0.002≦T ｃ / T ｍ ≦0.500 6. The optical device according to claim 1, wherein the following condition is satisfied:

7. The total optical length of the optical system is L, and the distance in the optical axis direction between the center of the most off-axis light beam in the meridional section and the intersection of the optical axis and the optical element is d. １ When 0.00≦d １ / L≦0.35 7. The optical device according to claim 1, wherein the following condition is satisfied:

8. The total optical length of the optical system is L, and the distance between the optical element and the aperture in the optical axis direction is d ２ When 0.00≦d ２ / L≦0.35 8. The optical device according to claim 1, wherein the following condition is satisfied:

9. The normalized radius and the normalized transmittance of the exit pupil of the optical system are expressed as r ｐ and D(r ｐ ), when the normalization radius is either 1 or 0.7, -6.0≦D’(r ｐ )≦1.0 9. The optical device according to claim 1, wherein the following condition is satisfied:

10. When D(1)<0.1, -0.80≦ave(D’(r ｐ ))[0.9,1]≦0.00 10. The optical device according to claim 9, wherein the following condition is satisfied:

11. The normalized radius and the normalized transmittance of the exit pupil of the optical system are expressed as r ｐ and D(r ｐ ) and -1.00≦ave(D’(r ｐ ))[0,0.2]≦0.10 11. The optical device according to claim 1, wherein the following condition is satisfied:

12. When the radius of the exit pupil of the optical system is maximum, the maximum and minimum values ​​of the transmittance on the optical axis of the exit pupil of the optical system when the transmittance distribution of the optical element is changed are denoted by T ｍａｘ and T ｍｉｎ , where p is the number of the optical elements included in the optical system, 0.3 ｐ <T ｍｉｎ / T ｍａｘ <1.0 12. The optical device according to claim 1, wherein the following condition is satisfied:

13. The optical element is provided with a plurality of electrodes arranged within an effective diameter, 13. An optical device according to claim 1, wherein when the transmittance distribution and the aperture radius of the optical element are set so that the transmittance of the exit pupil for the axial light beam of the optical system is maximized, the axial light beam does not pass through the boundary between each of the plurality of electrodes and an adjacent electrode.

14. 13. The optical device according to claim 1, wherein the optical element is provided with a single electrode having a predetermined film resistance in a direction perpendicular to the optical axis within an effective diameter.

15. 15. An imaging apparatus comprising: the optical device according to claim 1; and an imaging element that receives an image formed by the optical device.

Images