Soft focus filter, optical system, imaging apparatus, and information processing apparatus

Abstract

A soft focus filter includes a transparent substrate and a plurality of structures. A plurality of structures are formed on the transparent substrate and have a light diffusion function. The plurality of structures have a plurality of target values in an area range of 300 [mu] m2 to 200000 [mu] m2. The plurality of structures are arranged at an average pitch of 0.05 mm to 1 mm. The plurality of structures satisfy at least one of 50 nm or more in a wavelength range in which an absorbance is 0.3 or more in a wavelength region of 400 nm to 700 nm, and 0.2 or more in an average value of absorbance in the wavelength region of 400 nm to 700 nm.

Description

Technical Field

[0001] The present invention relates to a soft focus filter, an optical system, an imaging device, and an information processing device. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2002-303786 describes a soft focus imaging lens system in which a circular region whose center is on the optical axis of a lens element near a diaphragm is a smooth surface, and a peripheral portion other than the circular region is an annular strip-shaped light diffusing portion that cuts off high-frequency components of spatial frequency.

[0003] Japanese Unexamined Patent Application Publication No. 2013-257438 describes a soft focus filter. In this soft focus filter, a set of reference patterns having the same or different shapes are arranged on a transparent substrate in a spray pattern such that there is a portion where the shortest distance between adjacent reference patterns is less than or equal to 300 μm, thereby forming a transmitted light shielding pattern. The reference patterns are formed by line segments having a width of 10 to 200 μm in series and continuously or discontinuously. In addition, the transmitted light shielding pattern is randomly shaped such that the amount of transmitted light is locally non-uniform according to the local position, but is still shaped with a uniform dispersion ability as a whole.

[0004] However, according to the in-depth study by the present inventors, Japanese Unexamined Patent Application Publication Nos. 2002-303786 and 2013-257438 have room for improvement from the viewpoint of obtaining a suitable soft focus filter effect without being affected by the light flux diameter.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a soft focus filter, an optical system, an imaging device, and an information processing device that can achieve a suitable soft focus filter effect without being affected by the light flux diameter. Summary of the Invention

[0006] A soft focus filter according to an aspect of the present invention includes a transparent substrate and a plurality of structures. The plurality of structures are formed on the transparent substrate and have a light diffusion function. The plurality of structures have a plurality of target values in an area range of 300 μm 2 to 200,000 μm 2 The plurality of structures are arranged at an average pitch of 0.05 mm to 1 mm. The plurality of structures satisfy at least one of a wavelength range in which the absorbance in the wavelength region of 400 nm to 700 nm is greater than or equal to 0.3 and the wavelength range is greater than or equal to 50 nm, and an average value of the absorbance in the wavelength region of 400 nm to 700 nm is greater than or equal to 0.2.

[0007] According to one aspect of the present invention, there can be provided a soft focus filter, an optical system, an imaging device, and an information processing device that can achieve an appropriate soft focus filtering effect without being affected by the light flux diameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a conceptual diagram showing the basic structure of the soft focus filter of the present embodiment;

[0009] Figure 2 is a first conceptual diagram in the case where the structural distribution in the soft focus filter is defined by spatial frequency using blue noise characteristics and green noise characteristics;

[0010] Figure 3 is a second conceptual diagram in the case where the structural distribution in the soft focus filter is defined by spatial frequency using blue noise characteristics and green noise characteristics;

[0011] Figure 4A and 4B are lens diagrams of the optical system showing the first numerical example;

[0012] Figure 5 is a diagram showing the structure of the soft focus filter according to the first numerical example;

[0013] Figure 6A and 6B are lens diagrams of the optical system showing the second numerical example;

[0014] Figure 7 is a diagram showing the structure of the soft focus filter according to the second numerical example;

[0015] Figure 8A and Figure 8B is a first conceptual diagram showing the insertion and removal mechanism of the soft focus filter;

[0016] Figure 9A and 9B is a second conceptual diagram showing the insertion and removal mechanism of the soft focus filter;

[0017] Figure 10 is a first diagram showing an example of an imaging device equipped with the soft focus filter or the optical system of the present embodiment;

[0018] Figure 11 is a second diagram showing an example of an imaging device equipped with the soft focus filter or the optical system of the present embodiment; and

[0019] Figure 12 is an external perspective view showing an example of the interchangeable lens of the present embodiment.

[0020] The accompanying drawings are intended to depict exemplary embodiments of the present invention and should not be construed as limiting its scope. In the respective drawings, the same or similar reference numerals denote the same or similar components. Detailed Description of the Invention

[0021] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention.

[0022] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0023] In describing the preferred embodiments shown in the drawings, specific terms may be employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terms so selected, and it should be understood that each specific element includes all technical equivalents having the same function, operating in a similar manner and achieving similar results.

[0024] A detailed description of an embodiment of the present invention will be given below with reference to the accompanying drawings.

[0025] Prior Art and Its Technical Drawbacks

[0026] In order to achieve a soft focus effect by adding a filter, there are methods of refracting, diffracting, and scattering a part of the light flux. It is known that there are methods of causing refraction by forming minute irregularities on a transparent substrate, methods of forming patterns to cause diffraction or interference, methods of kneading powder to be scattered, and the like.

[0027] However, in such methods of imparting these shapes, the transparent substrate needs to have a certain thickness. For fine pattern printing, the transparent substrate needs to be made of glass, and there is a drawback that it also needs a certain thickness.

[0028] Furthermore, even after considering (examining) the prior art including the above-mentioned Japanese Unexamined Patent Application Publication Nos. 2002-303786 and 2013-257438, there is no method of combining the conditions of the structure (such as irregularities or patterns) on the transparent substrate and the transmission absorption characteristics of the structure, and there is room for improvement from the perspective of insufficient control factors for achieving the target soft focus effect. For example, Japanese Unexamined Patent Application Publication No. 2002-303786 does not clearly describe the conditions for appropriately achieving the soft focus effect without the adverse effects (side effects) of the specific structure of the light diffusing part. Additionally, in Japanese Unexamined Patent Application Publication No. 2013-257438, a certain area is required for pattern formation, and there is a concern about the change in the filter effect when it is narrowed in a small optical system.

[0029] Among photographers, there are a certain number of requirements for functions that can easily turn on and off the effect of a filter, and there is a need for a structure that automatically inserts and removes a filter in the camera instead of manually attaching and detaching the filter in front of or behind the lens. Moreover, regarding the soft focus effect, expression according to various shooting purposes is also required.

[0030] Considering the arrangement of the soft focus filter in the camera, in order to uniformly exhibit the filter effect across the entire screen, it is desirable to insert and remove the filter near the aperture in the lens system. However, there are the following drawbacks: the optical path length changes as the filter is inserted and removed in the lens system, and the aberration deteriorates. Therefore, it is necessary to make the filter thinner. In addition, in order to make the filter thinner, it is desirable to impart a filter function to the surface of a thin transparent substrate having a thin structure, and various conditions need to be appropriately set. In order to obtain various soft focus effects on the thin transparent substrate, appropriate condition setting is also required for the transmission absorption characteristics of the structure.

[0031] Technical idea of the present invention

[0032] The present inventor regarded the above drawbacks as important technical problems and has found how to optimally set various conditions and transmission absorption characteristics of a plurality of structures having a light diffusing function to be formed on a transparent substrate. As a result, a suitable soft focus filter effect can be achieved without being affected by the light flux diameter. For example, even if the soft focus filter is thinned and inserted into or removed from the aperture stop or its vicinity, deterioration of aberration due to changes in the optical path length can be prevented. For example, even when the aperture diameter is changed from the open state to the minimum state, the change in the filter effect can be reduced, and thus it is applicable to a small optical system in which the light flux is thin even in the open state of the aperture.

[0033] The soft focus filter of the embodiment has, as a basic structure, a transparent substrate and a plurality of structures formed on the transparent substrate, and the transparent substrate has a light diffusing function.

[0034] Figure 1 is a conceptual diagram showing the basic structure of the soft focus filter according to the present embodiment. As Figure 1 illustrated, the soft focus filter includes a transparent substrate 10 and a plurality of structures 20 formed on the transparent substrate 10 and having a light diffusing function. Figure 1Exemplarily, three structures 20X with a relatively large diameter, three structures 20Y with a relatively medium diameter, and three structures 20Z with a relatively small diameter are shown. As will be described in detail later, the structures 20X, 20Y, and 20Z are formed on the top surface of the transparent substrate 10 by, for example, inkjet printing using ultraviolet (UV) ink. As an example, the area of the structure 20X may be a "first target value", the area of the structure 20Y may be a "second target value", and the area of the structure 20Z may be a "third target value". It goes without saying that as the plurality of structures 20, multiple sets of structures with two levels or more than four levels of diameters (areas) can be formed.

[0035] Incidentally, in a set of structures having a specific target value, it is not required that the areas of the corresponding structures exactly coincide with each other, but may mean a set of structures having some variations with respect to the target value (area) due to an attempt to form a set of structures having that specific target value (area).

[0036] In the soft-focus filter of the present embodiment, the plurality of structures have multiple target values in the area range of 300 μm 2 to 200,000 μm 2 The plurality of structures preferably have multiple target values in the area range of 700 μm 2 to 71,000 μm 2 and more preferably have multiple target values in the area range of 950 μm 2 to 30,000 μm 2 The area range of the plurality of structures having multiple target values can be determined (measured) as follows. For example, various parameters such as the shape and size of the plurality of structures are set by inkjet printing using ultraviolet (UV) ink, so that the multiple target values can be determined (measured).

[0037] In the soft-focus filter of the present embodiment, the structures are arranged at an average pitch of 0.05 mm to 1 mm. The structures are preferably arranged at an average pitch of 0.1 mm to 0.7 mm, and more preferably arranged at an average pitch of 0.1 mm to 0.5 mm.

[0038] The multiple target values in the area range of 300 μm 2 to 200,000 μm 2 of the plurality of structures can be determined (measured) as follows. For example, various parameters such as the shape and size of the plurality of structures are set by inkjet printing using ultraviolet (UV) ink, so that the multiple target values can be determined (measured).

[0039] The average pitch of the plurality of structures can be determined (measured) as follows. As an example, if the area of an arbitrary region on the soft-focus filter is set to S (mm 2 ), and the number of structures (regardless of size) in this region is set to N, then the average pitch P can be expressed by the following formula.

[0040] P = (S / N) 1 / 2

[0041] Assuming that the average area occupied by the structure is square, which is defined as the average pitch, the above equation calculates the length of one side. In the case of calculating the average pitch by actual measurement, it is desirable to calculate the average pitch of the coverage area that is greater than or equal to 20% of the optical effective range of the filter so as not to be biased towards local measurements in the filter.

[0042] The structure has multiple target values in the area range of 300 μm 2 to 200,000 μm 2 and is arranged with an average pitch of 0.05 mm to 1 mm, thereby suppressing multiple images or color separation caused by diffraction or interference and enabling a natural soft focus effect.

[0043] If the area of the target value (e.g., defined by the lower limit value of the diameter) of multiple structures is less than 300 μm 2 , the contribution to the soft focus effect becomes too low. If the area of the target value (e.g., defined by the upper limit value of the diameter) of multiple structures exceeds 200,000 μm 2 , the light shielding region similar to the shadow projected by the structure generated in the optical path expands too wide, which adversely affects the quality of the blurred image.

[0044] If the average pitch of arranging the structures is less than 0.05 mm, the density of the structures is too high, and directional flare occurs according to the arrangement change to deteriorate the image quality, or the soft focus effect is too high to deteriorate the image quality. If the average pitch of arranging the structures exceeds 1 mm, either it is difficult to achieve the soft focus effect, or it becomes necessary to increase the size of the structures, and the light shielding region (such as the shadow projected by the structure generated in the optical path) expands excessively, which adversely affects the quality of the blurred image.

[0045] Preferably, the structures are randomly arranged such that the light transmittance is locally (when observed with a microscope) non-uniform according to the position and are arranged such that the dispersion rate is uniform as a whole (when observed macroscopically). In addition, the spatial frequency of the arrangement of multiple structures ideally has blue noise characteristics or green noise characteristics. The blue noise characteristics and green noise characteristics can be defined by, for example, the document "Digital Halftoning" (written by Robert Ulichney).

[0046] Figure 2 is a first conceptual diagram in the case of defining the distribution of the structures in the soft focus filter by spatial frequency using blue noise characteristics and green noise characteristics. Figure 2 As a simple example of the configuration of the structure, the spatial frequency characteristics of the configuration of the structure are conceptually shown. As Figure 2As illustrated, the spatial frequency characteristics of blue noise and green noise have peaks in frequency bands other than around 0 to 8 cycles / mm. Blue noise has higher peaks in higher frequency bands, and green noise has peaks around approximately 10 to 15 cycles / mm.

[0047] Figure 3 It is a second conceptual diagram in the case of defining the distribution of the structure in the soft focus filter by spatial frequency using blue noise characteristics and green noise characteristics. Figure 3 It is an explanatory diagram conceptually showing the spatial frequency characteristics of the threshold values set for each pixel of the blue noise dither matrix having blue noise characteristics, as a simple example of the adjustment of the dither matrix. The spatial frequency characteristics of the blue noise matrix have the maximum frequency component in the high frequency region where the length of one cycle is near the length of two pixels. Such spatial frequency characteristics are set considering the visual characteristics of humans. That is, considering the blue noise dither matrix and the visual characteristics of humans, namely, low sensitivity in the high frequency region, the storage position of the threshold value of the dither matrix is adjusted so that the maximum frequency component is generated in the high frequency region.

[0048] In Figure 3 the spatial frequency characteristics of the green noise matrix are further shown as a dashed curve. As shown, the spatial frequency characteristics of the green noise matrix have the maximum frequency component in the intermediate frequency region where the length of one cycle is from the length of two pixels to the length of ten or more pixels. Since the threshold value of the green noise matrix is set to have such spatial frequency characteristics, when determining the presence or absence of the formation of dots for each pixel by referring to the dither matrix having green noise characteristics, the dots are formed in a state adjacent to each other in units of several dots, and the dot groups are overall dispersed. In a printer such as a so-called laser printer where it is difficult to stably form fine dots of about one pixel, by referring to such a green noise matrix to determine the presence or absence of dot formation, the generation of isolated dots can be suppressed. As a result, an image with stable image quality can be output quickly. On the contrary, when determining the presence or absence of dot formation by a laser printer or the like, the threshold value adjusted to have green noise characteristics is set in the dither matrix to be referred to.

[0049] As described above, in the soft focus filter of the present embodiment, the structure is from 300μm 2 to 200000μm 2There are multiple target values within the area, arranged at an average spacing of 0.05 mm to 1 mm, randomly arranged locally (when observed under a microscope), such that the light transmittance is non-uniform according to the position, and arranged overall (when observed macroscopically) such that the dispersion ratio is uniform. As a result, due to the diffraction and interference phenomena occurring in each small structure, a blurring effect is given to the periphery of the basic image, where the light or shadow is blurred by the diffraction image. At the same time, although interference occurs due to the overlapping diffraction images caused by the diffraction phenomenon, the structure has multiple target values and the size varies, and in addition, the structures are randomly arranged. Therefore, even if interference occurs, the regular components are weak and it is less likely to produce multiple images, and overall, a soft focus effect such as a beautiful "blur" can be achieved.

[0050] In the soft focus filter of the present embodiment, the multiple structures satisfy one of the following conditions: the condition that the wavelength range with an absorbance greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm is greater than or equal to 50 nm, and the condition that the average value of the absorbance in the wavelength region of 400 nm to 700 nm in a predetermined region on the filter is greater than or equal to 0.2.

[0051] The multiple structures preferably have a wavelength range of greater than or equal to 70 nm with an absorbance greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm in a predetermined region on the filter.

[0052] The multiple structures preferably have an average absorbance of greater than or equal to 0.25 in the wavelength region of 400 nm to 700 nm.

[0053] By satisfying one of the two requirements of "having a wavelength range of greater than or equal to 50 nm with an absorbance greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm" and "the average value of the absorbance in the wavelength region of 400 nm to 700 nm is greater than or equal to 0.2", preferably satisfying both requirements, the light transmittance of the structure is controlled, and the factor for controlling the intensity of the diffused light in the filter unit for obtaining the soft focus effect increases, so that the target soft focus effect can be easily achieved.

[0054] Incidentally, "absorbance greater than or equal to 0.3" is equal to a state where the light transmittance is less than or equal to 50% when the incident light amount on the target object is 100%. Making the structure have this characteristic means that the transmitted light of the structure is lower than or equal to EV1 greater than the transmitted light of the properly exposed part, and by making the total wavelength region be greater than or equal to 50 nm, the occurrence of excessive light spots throughout the screen can be suppressed.

[0055] Incidentally, "absorbance greater than or equal to 0.2" is equal to a state where the light transmittance is less than or equal to 63% when the incident light amount on the target object is 100%. Allowing the structure to have this characteristic means that the transmitted light of the structure is on average lower than that of the properly exposed part by greater than or equal to about EV1 / 3, and over-spotting occurring throughout the screen can be suppressed.

[0056] As described above, diffraction or interference phenomena occur in the components shielded by small structures; however, the components transmitted by the structures are refracted to generate an optical path that is scattered relative to the normal optical path. The intensity and appearance of the soft-focus effect can be modified by controlling the light transmittance of the structure in the wavelength direction and the transmission direction. For example, in the case where the structure is formed of a black body having a completely zero transmittance, there is no component that is transmitted through the structure to become scattered light, the soft-focus effect of the entire screen is relatively weak, and it is possible to have an expression where the soft-focus effect only strongly appears on a high-luminance subject relative to proper exposure. On the contrary, in the case where the structure is formed of a completely transparent body having a transmittance of 100%, the soft-focus effect of the entire screen is relatively strong, without sparing the component that is transmitted through the structure to become scattered light, and the soft-focus effect easily appears even in a properly exposed subject.

[0057] In this example, assuming that the intensity of the incident light on the object (sample) is I0, the intensity of the transmitted light from the object (sample) is I, the optical path length in the object (sample) is L [cm], the molar extinction coefficient is ε [L / (mol·cm)], and the molar concentration [mol / L] is c, the absorbance (Abs) = -log(I / I0) = εcL can be calculated.

[0058] In the soft-focus filter of the present embodiment, preferably, the plurality of structures have at least three target values in the area range of 2500 μm 2 to 800000 μm 2 and the value obtained by dividing the maximum value among the at least three target values by the minimum value is greater than or equal to 2.25. When this condition is satisfied, the effect of suppressing multiple images can be fully demonstrated. When the condition is not satisfied, that is, in the area range of 300 μm 2 to 200000 μm 2 does not include at least three target values, and even if it includes at least three target values, and the value obtained by dividing the maximum value by the minimum value is less than 2.25, there is a possibility that the effect of suppressing multiple images is insufficient.

[0059] In the soft-focus filter of the present embodiment, the plurality of structures are preferably formed of ultraviolet (UV) ink. Thereby, the following structure that realizes the characteristics of the soft-focus filter of the present embodiment can be achieved. (X) The plurality of structures are in 300 μm2 ranging from 1 to 200,000 μm 2 has multiple target values within the area of. (Y) The structures are arranged at an average pitch of 0.05 mm to 1 mm. (Z) The multiple structures satisfy at least one of the following conditions: the condition that the wavelength range with an absorbance greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm is greater than or equal to 50 nm, or the condition that the average absorbance in the wavelength region of 400 nm to 700 nm in a predetermined area on the filter is greater than or equal to 0.2.

[0060] In inkjet printing, the ink droplets ejected from the inkjet head are directly ejected onto the medium, so the thickness of the medium does not need to be considered. In addition, since the position of the ink droplets can be controlled at the order of dozens of micrometers, inkjet printing is suitable for easily manufacturing structures on a thin transparent substrate to exhibit a filter effect. Inkjet printing is very suitable for mass production; however, since it is also a printing method without a master, it is easy to change the printing conditions according to the production model or individual, and inkjet printing is also suitable for producing various types in small quantities. In addition, as a characteristic of inkjet printing, there is a point that the color or concentration of the ink used can be appropriately adjusted. For example, not only K ink, but also various colors such as C, M, Y ink, R, G, B ink, or O (orange), G (green), W (white) can be used, and complex colors can be designed by mixing these pigments. In addition, the transmittance can be controlled by adjusting the dilution rate of the ink.

[0061] By manufacturing multiple structures through inkjet printing such as UV inkjet printing, microstructures can be formed while minimizing the thickness of the transparent substrate. In addition, according to inkjet printing, various expressions can be created individually by the soft-focus filter, and single or multiple soft-focus filters can also be accommodated in the camera housing. It is also easy to change the design values (diameter, diameter ratio, arrangement, etc.) of different structures for each individual. In addition, by appropriately adjusting the color or concentration of the ink, or controlling the dilution rate, the diffused light from the structure can be adjusted, and the degree of freedom of soft-focus expression can be improved.

[0062] In addition, the technical characteristics in the case of forming structures by inkjet printing (especially UV inkjet printing) include the following. By adjusting the concentration of the ink, an appropriate amount of light shielding for the filter can be achieved. In addition, by controlling the irradiation timing of the UV lamp, a structure shape suitable for the filter can be obtained. By adjusting the ejection waveform, the size of the structure can be gradually changed.

[0063] Note that the method of forming a plurality of structures on a transparent substrate (method of manufacturing a soft focus filter) is not limited to the form of the structure that diffuses light by jetting and fixing through an inkjet printer as described above, but various modes can be adopted. For example, a plurality of structures (manufacturing a soft focus filter) can also be formed on a transparent substrate by using various types of printing techniques.

[0064] Preferably, the soft focus filter of the present embodiment is held in such a manner that it can be inserted into the optical path of an optical system and removed from the optical path of the optical system, and satisfies the following conditional expression (1):

[0065] (1) (d * (Nd - 1)) / D < 0.040,

[0066] where

[0067] D: the air gap in the optical path of the optical system (the distance between the lens surface immediately before the soft focus filter and the lens surface immediately after the soft focus filter), into which the soft focus filter is inserted and removed from the air gap,

[0068] d: the thickness of the transparent substrate, and

[0069] Nd: the refractive index of the transparent substrate.

[0070] The conditional expression (1) defines a reduction in the thickness of the transparent substrate in combination with various conditions of a plurality of structures having a light diffusion function and an optimal setting of the transmission absorption characteristics, and thus defines a reduction in the thickness of the soft focus filter. By satisfying the conditional expression (1), it is possible to suppress changes in the optical path length and changes in aberration when the soft focus filter is inserted into the optical path of the optical system and removed from the optical path of the optical system, and excellent imaging performance and image quality can be achieved.

[0071] In order to impart a uniform soft focus effect to the entire screen, it is desirable to dispose the filter near the aperture stop where the light fluxes of all viewing angles are closest. By inserting the filter into the optical path and removing the filter from the optical path, the optical path length may change by the air gap for insertion and removal, whereby field curvature, spherical aberration, etc. may change, leading to deterioration of image quality. However, if the filter is thin, such aberration variation can be suppressed. By satisfying the conditional expression (1), it is possible to thin the soft focus filter and suppress the aberration variation within an allowable range. If the conditional expression (1) is not satisfied, the thinning of the soft focus filter is insufficient, and the aberration variation may exceed the allowable range.

[0072] The soft-focus filter of this embodiment is held at a position adjacent to the aperture stop in the optical path of the optical system (in the first numerical example described later, the soft-focus filter is inserted immediately before the aperture stop, and in the second numerical example described later, the soft-focus filter is inserted immediately after the aperture stop). As a result, the light fluxes of all viewing angles pass through substantially the same area of the filter, and a uniform filter effect can be imparted to the entire area of the captured screen. In particular, by holding the soft-focus filter of this embodiment at a position adjacent to the aperture stop in the optical path of the optical system and satisfying the above conditional expression (1), a more appropriate soft-focus effect can be achieved.

[0073] As described above, the soft-focus filter of this embodiment includes a transparent substrate and a plurality of structures formed on the transparent substrate and having a light diffusion function. The plurality of structures have a plurality of target values in an area range of 300 μm 2 to 200,000 μm 2 and are arranged at an average pitch of 0.05 mm to 1 mm. The plurality of structures satisfy at least one of the following: a wavelength range of greater than or equal to 50 nm with an absorbance of greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm or an average absorbance of greater than or equal to 0.2 in the wavelength region of 400 nm to 700 nm.

[0074] More specifically, the requirements of the soft-focus filter are specified by defining the physical properties of the soft-focus filter based on the absorbance of the structure for obtaining the soft-focus effect from the diffused light and the distribution of the structures in the soft-focus filter. The distribution of the structures in the soft-focus filter can be defined by spatial frequency using, for example, blue noise characteristics and green noise characteristics. In addition, the soft-focus filter is not an external filter, but is installed through an insertion and removal mechanism, where the soft-focus filter is inserted into the optical system during soft-focus imaging and retracted from the optical system during normal imaging.

[0075] Numerical Examples

[0076] Specific first and second numerical examples are shown. The meanings of the symbols in the first and second numerical examples are as follows. The glass types (glass materials) in the examples are the optical glass type names of HOYA Corporation (HOYA) and OHARA INC. (OHARA). The unit of length is [mm]. In this example, the reciprocal of the paraxial curvature radius (paraxial curvature) is set as C, the height from the optical axis is set as H, and the aspheric surface is defined by the following formula.

[0077] x = CH 2 / [1 + [1 - (1 + K)C 2 H 2 1 / 2 +A4H 4 +A6H​6 +A8H 8 +A 10 H 10 +

[0078] A 12 H 12 +A 14 H 14

[0079] f: The focal length of the entire system

[0080] F: F-number

[0081] w: Half field of view

[0082] Ya: Maximum image height

[0083] R: Radius of curvature

[0084] D: Surface interval

[0085] Nd: Refractive index at d-line

[0086] nd: Abbe number at d-line

[0087] BF: Back focal length

[0088] K: Aspheric conic constant

[0089] A4: Fourth-order aspheric coefficient

[0090] A6: Sixth-order aspheric coefficient

[0091] A8: Eighth-order aspheric coefficient

[0092] A10: Tenth-order aspheric coefficient

[0093] A12: Twelfth-order aspheric coefficient

[0094] A14: Fourteenth-order aspheric coefficient

[0095] First numerical example

[0096] Figure 4A and Figure 4B Tables 1 to 3 show the optical system of the first numerical example. Figure 4A is a lens structure diagram in a state where the soft focus filter SFF is inserted into the optical system, and Figure 4B is a lens structure diagram in a state where the soft focus filter SFF is retracted from the optical system. Table 1 shows surface data (lens data), Table 2 shows aspheric data, and Table 3 shows focal length data.

[0097] The optical system of the first numerical example includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power. Between the fourth lens group G4 and the image plane (designed image plane) I, filters F1 and F2 are arranged. The filters F1 and F2 include, for example, flat members such as a low-pass filter and an infrared cut-off filter, or cover glasses of imaging elements. In the following surface data, the filters F1 and F2 are described as optical glasses.

[0098] An aperture stop SP for light quantity adjustment is provided between the second lens group G2 and the third lens group G3. In addition, a soft focus filter SFF is provided between the second lens group G2 and the third lens group G3 in a manner that it can be inserted (opened) and retracted (closed), and is located immediately before (near) the aperture stop SP. Figure 4A The inserted (opened) state of the soft focus filter SFF is shown, and Figure 4B The retracted (closed) state of the soft focus filter SFF is shown.

[0099] The first lens group G1 includes a negative meniscus lens 11 that is convex toward the object side.

[0100] The second lens group G2 includes, in order from the object side, a negative meniscus lens 21 that is convex toward the image side, a biconvex positive lens 22, and a biconcave negative lens 23. The negative meniscus lens 21 has an aspherical surface on the object side. The biconvex positive lens 22 and the biconcave negative lens 23 are combined with each other.

[0101] The third lens group G3 includes, in order from the object side, a biconvex positive lens 31, a positive meniscus lens 32 that is convex toward the image side, and a biconcave negative lens 33. The positive meniscus lens 32 and the biconcave negative lens 33 are combined with each other.

[0102] The fourth lens group G4 includes a positive meniscus lens 41 that is convex toward the image side. The positive meniscus lens 41 has aspherical surfaces on both sides.

[0103] Table 1 f = 13.9, f = 3.61, w = 46.3, Ya = 14.127, BF = 0.7

[0104]

[0105] *Rotationally symmetric aspherical surface

[0106] Table 2

[0107]

[0108] Table 3

[0109]

[0110] Figure 5 This is a diagram showing the structure of the soft focus filter SFF that presents the first numerical example. More specifically, Figure 5 This shows one aspect of the structure on the transparent substrate included in the soft focus filter SFF of the first numerical example. The substrate is a polycarbonate sheet with a thickness of 0.05 mm and a refractive index of 1.58. The structure is formed to have three types of diameters: small diameter = 70 μm, medium diameter = 90 μm, large diameter = 150 μm. In terms of area, small diameter ≈ 3848 μm 2 , medium diameter ≈ 6362 μm 2 , large diameter ≈ 17671 μm 2 . The average pitch is about 0.22 mm. The soft focus filter SFF of the first numerical example is disposed adjacent to the object side of the aperture stop SP, and the on-axis luminous flux on the soft focus filter SFF is f4.58 mm. The diameter of the structure on the soft focus filter SFF is about 1.5% to 3.3% of the on-axis luminous flux. If the luminous flux of this structure is too large, the shadow of the structure appears significantly when the image is blurred, thereby degrading the quality of the blurred image. Therefore, the size of the structure on the soft focus filter SFF is desirably less than 10% of the diameter of the on-axis luminous flux. The structure on the transparent substrate is formed of ultraviolet (UV) ink, and black ink with an average absorbance of 0.83 in the wavelength range of 400 nm to 700 nm is used. By forming the structure with a material having a relatively large absorbance, the soft filter effect can be suppressed and excessive flare with respect to bright subjects can be suppressed.

[0111] Table 4 shows the corresponding numerical values of the conditional expressions (operation results) regarding the soft focus filter SFF of the first numerical example and the optical system including the same.

[0112] Table 4

[0113] Area of the structure: small diameter ≈ 3848 μm 2 , medium diameter ≈ 6362 μm 2 , large diameter ≈ 17671 μm 2 Average pitch: 0.22 mm

[0114] Wavelength range having an absorbance of 0.3 or more in the wavelength range of 400 nm to 700 nm: 300 nm (i.e., the entire region of 400 nm to 700 nm)

[0115] Average absorbance in the wavelength range of 400 nm to 700 nm: 0.83

[0116] Number of target values of the structure area: 3

[0117] Ratio of the maximum value to the minimum value of the target area: 4.59 (= 17671 μm 2 / 3848 μm 2 )

[0118] (d * (Nd - 1)) / D = (0.05 * (1.58 - 1)) / 2.735 ≈ 0.011

[0119] Second numerical example

[0120] Figure 6A and Figure 6B Tables 5 to 7 show the optical system of the second numerical example. Figure 6A is a lens structure diagram in a state where the soft focus filter SFF' is inserted into the optical system, and Figure 6B is a lens structure diagram in a state where the soft focus filter SFF' is retracted from the optical system. Table 5 shows surface data (lens data), Table 6 shows aspherical data, and Table 7 shows focal length data.

[0121] The optical system of the second numerical example includes, in order from the object side, a first lens group G1' having a negative refractive power, a second lens group G2' having a positive refractive power, and a third lens group G3' having a negative refractive power. Filters F1' and F2' are arranged between the third lens group G3' and the image plane (designed image plane) I'. Filters F1', F2' include, for example, flat members such as a low-pass filter and an infrared cut-off filter, or a cover glass of an imaging element. In the following surface data, filter F1' is described as an optical filter, and F2' is described as an optical glass.

[0122] An aperture stop SP' for light quantity adjustment is provided between the first lens group G1' and the second lens group G2'. In addition, the soft focus filter SFF' is provided between the first lens group G1' and the second lens group G2' in a manner that can be inserted (opened) and retracted (closed), and is located immediately after (near) the aperture stop SP'. Figure 6A shows the inserted (opened) state of the soft focus filter SFF', and Figure 6B shows the retracted (closed) state of the soft focus filter SFF'.

[0123] The first lens group G1' includes, in order from the object side, a negative meniscus lens 11' convex toward the object side, a biconcave negative lens 12', and a biconvex positive lens 13'. The negative meniscus lens 11' has an aspherical surface on the image side. The biconcave negative lens 12' and the biconvex positive lens 13' are combined with each other.

[0124] The second lens group G2' includes, in order from the object side, a positive lens 21' with a biconvex shape, a negative lens 22' with a biconcave shape, and a positive meniscus lens 23' convex toward the image side. The positive meniscus lens 23' has aspherical surfaces on both sides. The biconvex positive lens 21' and the biconcave negative lens 22' are combined with each other.

[0125] The third lens group G3′ includes a negative meniscus lens 31′ convex toward the image side. The negative meniscus lens 31' has aspherical surfaces on both sides.

[0126] Table 5 f = 18.35, f = 2.87, w = 37.9, Ya = 14.13, BF = 0.7

[0127]

[0128] *Rotationally symmetric aspherical surface

[0129] Table 6

[0130]

[0131] Table 7

[0132] Focal length

[0133] The first lens group 31.65

[0134] The second lens group 29.44

[0135] The third lens group -51.91

[0136] Figure 7 It is a diagram showing the structure of the soft focus filter SFF' of the second numerical example. More specifically, Figure 7 One aspect of the structure on the transparent substrate included in the soft focus filter SFF' of the second numerical example is shown. The substrate is a cycloolefin polymer sheet with a thickness of 0.013 mm and a refractive index of 1.55. The structure is formed to have three target types of diameters: small diameter = 50 μm, medium diameter = 80 μm, and large diameter = 120 μm. In terms of area, the small diameter ≈ 1963 μm 2 , medium diameter ≈ 5027 μm 2 , and large diameter ≈ 11310 μm 2。The average pitch is approximately 0.40 mm. The soft focus filter SFF' of the second numerical example is disposed adjacent to the image side of the aperture stop SP', and the on-axis luminous flux on the soft focus filter SFF' is f6.32 mm. The diameter of the structure on the soft focus filter SFF' is approximately 0.8% to 1.9% of the on-axis luminous flux. The structure on the transparent substrate is formed of ultraviolet (UV) ink, and black ink having an average absorbance of 0.83 in the wavelength region of 400 nm to 700 nm is used. By forming the structure with a material having a relatively large absorbance, the soft filter effect can be suppressed and excessive flare with respect to a bright subject can be suppressed. Note that the absorbance of the material of the structure on the transparent substrate can be selected differently according to the target soft filter effect. For example, using yellow having a relatively low average value of 0.27 for the absorbance in the range of 400 nm to 700 nm enables a flash feeling to be caused even under relatively dark exposure conditions, and using cyan having an average value of 0.49 for the absorbance in the range of 400 nm to 700 nm enables an intermediate effect between yellow and black to be achieved.

[0137] Table 8 shows the corresponding numerical values of the conditional expressions (operation results) for the soft focus filter SFF' of the second numerical example and the optical system including the same.

[0138] Table 8

[0139] Area of structure: small diameter ≈ 1963 μm 2 , medium diameter ≈ 5027 μm 2 , large diameter ≈ 11310 μm 2

[0140] Average pitch: 0.40 mm

[0141] Wavelength range having an absorbance of 0.3 or more in the wavelength region of 400 nm to 700 nm: 300 nm for black (i.e., the entire region of 400 nm to 700 nm)

[0142] 80 nm for yellow (400 nm to 480 nm)

[0143] 146 nm for cyan (554 nm to 700 nm)

[0144] Average absorbance in the wavelength region of 400 nm to 700 nm:

[0145] 0.83 for black

[0146] 0.27 for yellow

[0147] 0.49 for cyan

[0148] Number of target values of structure area: 3

[0149] Ratio of the maximum value to the minimum value of the target area: 5.76 (= 11310 μm 2 / 1963 μm 2 )

[0150] (d * (Nd - 1)) / D = (0.013 * (1.55 - 1)) / 2.31 ≈ 0.003

[0151] Switching mechanism for insertion (opening) and retraction (closing) of the soft focus filter

[0152] For example, the soft focus filters SFF and SFF' in the above first and second numerical examples are respectively built in the shutter units provided near the aperture stops SP and SP', and a structure is adopted in which "set on the optical axis" and "retracted from the optical axis" can be performed by a drive system included in the shutter unit. By adopting this structure, it is possible to commonly configure the mechanism and power supply for inserting and retracting the soft focus filter with respect to the optical axis position within the shutter unit, and it is possible to make the imaging optical device compact. In addition, in response to an operation from the camera body, the soft focus filter can be retracted from the optical axis during normal imaging, and when the filter effect is turned on, the soft focus filter can be inserted on the optical axis to cover the entire aperture stop.

[0153] Figure 8A and Figure 8B is a first conceptual diagram showing an exemplary insertion and removal mechanism of the soft focus filter SFF". In this example, an insertion and removal mechanism equipped with a retraction mechanism will be described, which reduces the thickness when the lens barrel is accommodated by removing the soft focus filter SFF" from the optical axis when the lens barrel is accommodated. However, there is freedom in specific aspects of the insertion and removal mechanism, and various design modifications can be made.

[0154] In Figure 8A and Figure 8BIn the figure, the left side represents the front side (object side) in the optical axis direction, and the right side represents the rear side (image side) in the optical axis direction. The insertion and removal mechanism includes a filter holding unit 1000 that holds the soft focus filter SFF”, a front lens holding unit 2000 that holds the front lens GF, and a rear lens holding unit 3000 that holds the rear lens GR. The front lens GF corresponds to, for example, the second lens group G2 of the first numerical example or the first lens group G1’ of the second numerical example, and the rear lens GR corresponds to, for example, the third lens group G3 of the first numerical example or the second lens group G2’ of the second numerical example. A guide member 1100 having a guide hole is formed in the filter holding unit 1000, a guide member 2100 having a guide hole is formed in the front lens holding unit 2000, and a guide member 3100 having a guide hole is formed in the rear lens holding unit 3000. The insertion and removal mechanism has a guide shaft GS that extends parallel to the optical axis of the optical system, and the guide shaft GS is inserted into the guide holes of the guide member 1100 of the filter holding unit 1000, the guide holes of the guide member 2100 of the front lens holding unit 2000, and the guide holes of the guide member 3100 of the rear lens holding unit 3000. The guide shaft GS is rotationally driven to switch between the feeding state and the storage state of the lens barrel. As the guide shaft GS rotates, the front lens holding unit 2000 and the rear lens holding unit 3000 can move in the optical axis direction along the guide shaft GS. In addition, as the guide shaft GS rotates, the filter holding unit 1000 moves in the optical axis direction along the guide shaft GS and rotates around the guide shaft GS, whereby the filter holding unit 1000 can be inserted into the optical path of the optical system and removed from the optical path of the optical system.

[0155] As Figure 8A shown, when feeding the lens barrel, the filter holding unit 1000 (soft focus filter SFF”), the front lens holding unit 2000 (front lens GF), and the rear lens holding unit 3000 (rear lens GR) are fed to a predetermined position along the guide shaft GS parallel to the optical axis of the optical system. Even in this feeding state, when soft focus imaging is not performed, the filter holding unit 1000 (soft focus filter SFF”) retracts from the optical path of the optical system. On the other hand, when soft focus imaging is performed, the filter holding unit 1000 (soft focus filter SFF”) is inserted into the optical path of the optical system by the rotational drive of the guide shaft GS, that is, between the front lens holding unit 2000 (front lens GF) and the rear lens holding unit 3000 (rear lens GR). That is, only when soft focus imaging is performed, the filter holding unit 1000 (soft focus filter SFF”) is inserted into the optical path of the optical system. Figure 8A The state in which the filter holding unit 1000 (soft focus filter SFF”) is inserted into the optical path of the optical system is shown.

[0156] As Figure 8BAs shown, when the lens barrel is accommodated, the filter holding unit 1000 (soft focus filter "SFF") retracts from the optical path of the optical system by the rotational drive of the guide shaft GS. Further, as the lens barrel retracts and the optical system is accommodated, the filter holding unit 1000 (soft focus filter "SFF"), the front lens holding unit 2000 (front lens "GF"), and the rear lens holding unit 3000 (rear lens "GR") are accommodated along the guide shaft GS until a predetermined position. Comparing the feeding state of Figure 8A with the accommodation state of Figure 8B , it can be seen that the former has a larger gap between the front lens holding unit 2000 (front lens "GF") and the rear lens holding unit 3000 (rear lens "GR"), and the latter has a smaller gap between the front lens holding unit 2000 (front lens "GF") and the rear lens holding unit 3000 (rear lens "GR").

[0157] In this way, including the guide shaft GS parallel to the optical axis of the optical system, the soft focus filter "SFF" is mounted on the guide shaft GS. Thus, the soft focus filter "SFF" can also be fed or retracted as the lens barrel is fed or retracted, and the soft focus filter "SFF" can be inserted onto the optical axis or retracted from the optical axis by the rotation of the guide shaft GS.

[0158] Note that the position where the soft focus filter is inserted or removed in the lens barrel is inside the camera body in the state where the lens barrel is fed (i.e., in the state where the soft focus filter is retracted from the optical axis), and a hole for inserting the soft focus filter is required in the lens barrel. Since even in the state where the lens barrel is fed, the part of the lens barrel having the hole is inside the camera body, the part of the lens barrel cannot be recognized from the outside. In Figure 8A , the line defining the inside and outside of the camera body is depicted by a single-dot dash line, and the line defining the inside and outside of the lens barrel is depicted by a double-dot dash line. The left side of the single-dot dash line is the outside of the camera body, and the right side of the single-dot dash line is the inside of the camera body. The upper side of the double-dot dash line is the outside of the lens barrel, and the lower side of the double-dot dash line is the inside of the lens barrel. Even when the filter holding unit 1000 (soft focus filter "SFF") retracts from the optical path of the optical system in the state where the lens barrel is fed, the filter holding unit 1000 (soft focus filter "SFF") is located inside the camera body and thus cannot be visually recognized from the outside.

[0159] Figure 9A and 9B are the second conceptual diagrams showing the insertion and removal mechanism of the soft focus filter. As shown in Figure 9A and 9BAs shown, the shutter unit 30 is disposed between the front lens GF and the rear lens GR (at the boundary therebetween), and a circular hole formed in the central portion of the shutter unit 30 constitutes the aperture stop SP” of the optical system. The aperture blades, shutter blades, and soft focus filter are accommodated in the peripheral edge portion of the circular hole forming the aperture stop SP”, and these aperture blades, shutter blades, and soft focus filter move back and forth as needed between the peripheral edge portion of the circular hole forming the aperture stop SP” and the inside of the circular hole forming the aperture stop SP”, as shown by the arrows in Figure 9A As shown.

[0160] Insertion position of the soft focus filter

[0161] In the above embodiment, the case where the insertion position of the soft focus filter is set to the aperture stop or near it has been described as an example (in the first numerical example, the soft focus filter SFF is inserted immediately before the aperture stop SP, and in the second numerical example, the soft focus filter SFF’ is inserted immediately after the aperture stop SP’). On the other hand, although a certain level of soft focus effect can be obtained even when the soft focus filter is inserted at a position far from the aperture stop, from the viewpoints of appropriately inserting the soft focus filter on the optical axis of the optical system or removing it from the optical axis of the optical system while reducing the size (diameter) of the soft focus filter, considering the light flux, it is most preferable to insert the soft focus filter at or near the aperture stop.

[0162] Application examples of digital cameras, interchangeable lenses, etc.

[0163] Referring to Figure 10 And Figure 11 , a digital camera (imaging device) 100 equipped with the soft focus filter or optical system of this embodiment will be described.

[0164] The digital camera 100 includes a camera body (housing) 101, an imaging lens 102, a viewfinder 103, a flash 104, a shutter button 105, a power button 106, a liquid crystal monitor 107, operation buttons 108, and a memory card slot 109.

[0165] The camera body 101 houses the components of the digital camera 100. The imaging lens 102 is, for example, a unit obtained by incorporating the optical system of the present embodiment into a lens barrel and / or an interchangeable lens. The viewfinder 103 is a viewing window for determining the subject or composition. The flash 104 emits a flash when shooting at night or in the dark. The shutter button 105 is a physical switch for taking a shot with the digital camera 100. The power button 106 is a physical switch for turning on and off the power of the digital camera 100. The liquid crystal monitor 107 displays images taken by the digital camera 100 and the like. The operation button 108 is a physical switch for setting the shooting mode and the like of the digital camera 100. The memory card slot 109 is a slot into which a memory card or the like for storing images taken by the digital camera 100 is inserted.

[0166] The digital camera 100 includes a central processing unit 111, an image processing unit 112, a light receiving element 113, a signal processing unit 114, a semiconductor memory 115, and a communication card 116 as functional components inside the camera body 101.

[0167] The central processing unit 111 performs various types of arithmetic processing inside the digital camera 100. The image processing device 112 performs various types of image processing on the images taken by the digital camera 100. The light receiving element 113 receives external light for photometry processing. The signal processing unit 114 performs various types of signal processing on shooting instruction signals, image processing signals, and the like. The semiconductor memory 115 constitutes a temporary storage area for the images taken by the digital camera 100. The communication card 116 is used to enable wireless communication with external devices such as a PC. The digital camera 100 functions as an information processing device that performs various types of processing on the captured image information.

[0168] Figure 12 is an external perspective view showing an example of the interchangeable lens (lens barrel) 102 of the present embodiment. As Figure 12 shown, the interchangeable lens 102 includes a lens holding barrel 102X and an optical system held by the lens holding barrel 102X. Figure 12 shows the lens 11 or 11' disposed closest to the object side in the first lens group G1 or G1' in the optical system.

[0169] The structure of the digital camera 100 described here is merely an example, and various design modifications can be made (there is freedom in the specific aspects of the digital camera 100). It can also be applied to information processing devices equipped with an imaging function.

[0170] The optical system of the present embodiment can be applied to, for example, interchangeable lenses, portable information terminal devices, imaging machines, silver halide cameras, optical sensors, projection optical systems (projectors), etc. in addition to the above digital camera 100.

[0171] In the following, an invention described in the claims originally filed in this application will be added.

[0172] [Supplementary Note 1]

[0173] A soft-focus filter, comprising:

[0174] A transparent substrate; and

[0175] A plurality of structures formed on the transparent substrate and having a light diffusion function, wherein:

[0176] The plurality of structures have a plurality of target values within an area range of 300 μm 2 to 200,000 μm 2 ,

[0177] The structures are arranged at an average pitch of 0.05 mm to 1 mm, and

[0178] The plurality of structures satisfy at least one of the following: a wavelength range having an absorbance greater than or equal to 0.3 in the wavelength region of 400 nm to 700 nm is greater than or equal to 50 nm, and an average value of the absorbance in the wavelength region of 400 nm to 700 nm is greater than or equal to 0.2.

[0179] [Supplementary Note 2]

[0180] The soft-focus filter according to Supplementary Note 1,

[0181] wherein the structures are randomly arranged such that the light transmittance is locally non-uniform according to position, and are arranged such that the dispersion ratio is uniform as a whole.

[0182] [Supplementary Note 3]

[0183] The soft-focus filter according to Supplementary Note 1 or 2, wherein

[0184] The plurality of structures have at least three target values within an area range of 300 μm 2 to 200,000 μm 2 , and

[0185] A value obtained by dividing the maximum value of at least three target values by the minimum value of at least three target values is greater than or equal to 2.25.

[0186] [Supplementary Note 4]

[0187] The soft-focus filter according to any one of Supplementary Notes 1 to 3,

[0188] wherein the plurality of structures are formed of ultraviolet (UV) ink.

[0189] [Supplementary Note 5]

[0190] The soft focus filter according to any one of Supplementary Notes 1 to 4, wherein

[0191] the soft focus filter is held in a manner that it can be inserted into and removed from the optical path of the optical system, and

[0192] the following conditional expression (1) is satisfied:

[0193] (1) (d * (Nd - 1)) / D < 0.040,

[0194] wherein

[0195] D: the air gap in the optical path of the optical system, into which and from which the soft focus filter is inserted and removed,

[0196] d: the thickness of the transparent substrate, and

[0197] Nd: the refractive index of the transparent substrate.

[0198] [Supplementary Note 6]

[0199] The soft focus filter according to any one of Supplementary Notes 1 to 5,

[0200] wherein the soft focus filter is held at a position adjacent to the aperture stop in the optical path of the optical system.

[0201] [Supplementary Note 7]

[0202] An optical system comprising the soft focus filter according to any one of Supplementary Notes 1 to 6.

[0203] [Supplementary Note 8]

[0204] An imaging device comprising the soft focus filter according to any one of Supplementary Notes 1 to 6.

[0205] [Supplementary Note 9]

[0206] An information processing device comprising the soft focus filter according to any one of Supplementary Notes 1 to 6.

[0207] The above embodiments are illustrative and do not limit the present invention. Therefore, many additional modifications and variations are possible in view of the above teachings. For example, at least one element of the different illustrative and exemplary embodiments herein can be combined with each other or replaced with each other within the scope of the present disclosure and the appended claims. In addition, the features of the components of the embodiments (such as the quantity, position, and shape) are not limited to the described embodiments and can thus be preferably arranged. Therefore, it should be understood that within the scope of the appended claims, the disclosure of the present invention can be implemented in a manner different from that specifically described herein.

Claims

1. A soft-focus filter, comprising: A transparent substrate; And A plurality of structures formed on the transparent substrate and having a light diffusion function, wherein Multiple structures have multiple target values within an area ranging from 300 μm 2 to 200,000 μm 2 and have multiple target values within the area range of The plurality of structures are arranged at an average pitch of 0.05 mm to 1 mm, and The plurality of structures satisfy at least one of the following: the wavelength range having an absorbance greater than or equal to 0.3 is greater than or equal to 50 nm in the wavelength region of 400 nm to 700 nm, and the average value of the absorbance is greater than or equal to 0.2 in the wavelength region of 400 nm to 700 nm.

2. The soft-focus filter according to claim 1, Wherein the plurality of structures are randomly arranged such that the light transmission amount is locally non-uniform according to the position and arranged such that the dispersion ratio is globally uniform.

3. The soft-focus filter according to claim 1 or 2, wherein The multiple structures have at least three target values within an area ranging from 300 μm 2 to 200000 μm 2 and The value obtained by dividing the maximum value of at least three target values by the minimum value of at least three target values is greater than or equal to 2.

25.

4. The soft-focus filter according to claim 1 or 2, Wherein the plurality of structures are formed of ultraviolet (UV) ink.

5. The soft-focus filter according to claim 1 or 2, wherein The soft-focus filter is held in a manner that can be inserted into and removed from the optical path of the optical system, and Satisfies the following conditional expression (1): (1) (d * (Nd - 1)) / D < 0.040 Wherein D: The air gap in the optical path of the optical system, into which the soft-focus filter is inserted and removed from the air gap, d: The thickness of the transparent substrate, and Nd: The refractive index of the transparent substrate.

6. The soft-focus filter according to claim 1 or 2, Wherein the soft-focus filter is held at a position adjacent to the aperture stop in the optical path of the optical system.

7. An optical system, comprising the soft-focus filter according to claim 1 or 2.

8. An imaging device, comprising the soft-focus filter according to claim 1 or 2.

9. An information processing device, comprising the soft-focus filter according to claim 1 or 2.

Images