Optical system and image pickup apparatus

Abstract

[Problem] To provide an optical system that is compact and has high optical performance. [Solution] An optical system (100) comprises, in order from the object side to the image side, a first transmission / reflection surface (HM1), a quarter-wave plate (QWP), and a second transmission / reflection surface (HM2). The optical system is a primary imaging system. Light from the object side is sequentially transmitted through the first transmission-reflection surface and the quarter-wave plate, reflected by the second transmission-reflection surface toward the object side, transmitted through the quarter-wave plate, reflected by the first transmission-reflection surface toward the image side, sequentially transmitted through the quarter-wave plate and the second transmission-reflection surface, and traveling toward the image side. A distance (zm1) on the optical axis from the first transmissive-reflective surface to the image surface and a focal length (f) of the optical system satisfy a predetermined conditional expression.

Description

Technical Field

[0001] The present invention relates to optical systems. Background Art

[0002] Optical systems with reduced size and good optical performance have recently been required for use in imaging devices such as smartphones and mirrorless cameras. Examples of optical systems with reduced total optical length and good optical performance include the periscope optical system disclosed in Patent Document 1 and the catadioptric optical system disclosed in Patent Document 2.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: WO2019 / 156933

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-015712 Summary of the Invention

[0007] Problems to be solved by the present invention

[0008] However, it is difficult to reduce the size of the periscope optical system disclosed in Patent Document 1 in the direction perpendicular to the optical axis. In addition, in the catadioptric optical system disclosed in Patent Document 2, it is difficult to enlarge the light receiving element relative to the transmission hole in the main reflector, and it is difficult to obtain high optical performance relative to the size of the optical system.

[0009] The present invention provides an optical system that is compact and has high optical performance.

[0010] Solutions to this problem

[0011] According to one aspect of the present invention, an optical system includes, in order from the object side to the image side, a first transflective surface, a quarter-wave plate, and a second transflective surface. The optical system is a primary imaging system. Light from the object side sequentially transmits through the first transflective surface and the quarter-wave plate, is reflected toward the object side by the second transflective surface, transmits through the quarter-wave plate, is reflected toward the image side by the first transflective surface, sequentially transmits through the quarter-wave plate and the second transflective surface, and travels toward the image side. The optical system satisfies the following conditional expression:

[0012] 0.10≤zm1 / f≤0.68

[0013] Wherein, zm1 is the distance from the first transflective surface to the image plane on the optical axis, and f is the focal length of the optical system.

[0014] Other objects and features of the present invention will become apparent from the following description of embodiments.

[0015] Effects of the Invention

[0016] The present invention can provide an optical system that is compact and has high optical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram showing the light path in the optical system.

[0018] Figure 2 is a schematic diagram showing the light path in the optical system.

[0019] Figure 3 is a cross-sectional view of an optical system according to Example 1.

[0020] Figure 4 : are aberration diagrams of the optical system according to Example 1.

[0021] Figure 5 is a cross-sectional view of an optical system according to Example 2.

[0022] Figure 6 2 are aberration diagrams of the optical system according to Example 2.

[0023] Figure 7 is a cross-sectional view of an optical system according to Example 3.

[0024] Figure 8 3 are aberration diagrams of the optical system according to Example 3.

[0025] Figure 9 is a cross-sectional view of an optical system according to Example 4.

[0026] Figure 10 4 are aberration diagrams of the optical system according to Example 4.

[0027] Figure 11 is a cross-sectional view of an optical system according to Example 5.

[0028] Figure 12 : are aberration diagrams of the optical system according to Example 5.

[0029] Figure 13 is a cross-sectional view of an optical system according to Example 6.

[0030] Figure 14 : are aberration diagrams of the optical system according to Example 6.

[0031] Figure 15 is a cross-sectional view of an optical system according to Example 7.

[0032] Figure 16 : are aberration diagrams of the optical system according to Example 7.

[0033] Figure 17is a cross-sectional view of an optical system according to Example 8.

[0034] Figure 18 : are aberration diagrams of the optical system according to Example 8.

[0035] Figure 19 is a cross-sectional view of an optical system according to Example 9.

[0036] Figure 20 : are aberration diagrams of the optical system according to Example 9.

[0037] Figure 21 is a cross-sectional view of an optical system according to Example 10.

[0038] Figure 22 1 and 2 are aberration diagrams of the optical system according to Example 10.

[0039] Figure 23 is a cross-sectional view of an optical system according to Example 11.

[0040] Figure 24 2 are aberration diagrams of the optical system according to Example 11.

[0041] Figure 25 is a cross-sectional view of an optical system according to Example 12.

[0042] Figure 26 14 is an aberration diagram of the optical system according to Example 12. DETAILED DESCRIPTION

[0043] Referring now to the accompanying drawings, a detailed description will be given of examples according to the present invention.

[0044] The imaging optical system according to each example is an optical system that forms an image of an object on an image plane and acquires the image using a solid-state image sensor or a photosensitive film arranged on the image plane.

[0045] The imaging optical system according to each example includes a first transflective surface, a quarter-wave plate (QWP), and a second transflective surface, arranged sequentially from the object side to the image side. Light from the object side sequentially transmits through the first transflective surface and the QWP and is reflected by the second transflective surface. The light then transmits through the QWP and is reflected by the first transflective surface, then transmits through the QWP and the second transflective surface and reaches an imaging element such as a solid-state image sensor or a photosensitive film.

[0046] Here, the first transflective surface and the second transflective surface may not have a transmittance of 50% and a reflectance of 50%. The ratio of transmittance to reflectance for randomly polarized light is preferably in the range of 1:3 to 3:1. Randomly polarized light is light with Stokes parameters S0 = 1 and S1 = S2 = S3 = 0. The first transflective surface and the second transflective surface may absorb light.

[0047] Lenses may be formed or bonded on both sides or one side of each transflective surface.

[0048] For example, birefringent polymer films or liquid crystal alignment layers can be used as QWPs. Laminates of such polymer films or liquid crystal alignment layers can also be used as QWPs. Properly laminating these can provide a phase shift close to a quarter wavelength over a wide wavelength range. In addition to the above, inorganic wave plates from Dexerials can also be used as QWPs.

[0049] A QWP can be configured by bonding it to a first transflective surface or a second transflective surface. The QWP can also be configured as a separate component from these transflective surfaces. For example, the film can be inserted directly into the optical path, or the film can be bonded to a glass sheet and then inserted into the optical path. Lenses can be formed or bonded to one or both sides of the QWP. For example, lenses can be formed on one or both sides of an inorganic wave plate as a substrate using wafer-level optics technology.

[0050] The imaging optical system according to each example satisfies the following conditional expression (1), where zm1 is the distance on the optical axis from the first transflective surface to the image plane, and f is the focal length of the imaging optical system.

[0051] 0.10≤zm1 / f≤0.68 (1)

[0052] In the case where zm1 / f becomes lower than the lower limit of conditional expression (1), the optical path length of the return portion of the light is not sufficiently ensured, and the total length of the imaging optical system increases. In the case where zm1 / f becomes higher than the upper limit of conditional expression (1), the focal length (refractive power) of the first transflective surface and the second transflective surface cannot be increased. The small focal length of these transflective surfaces increases the focal length ratio due to refraction. Therefore, chromatic aberration increases and image quality deteriorates. In addition, due to the small focal length of these transflective surfaces, it becomes difficult to significantly bend light incident from outside the axis. Therefore, the imaging circle becomes smaller, and it becomes difficult for the imaging system to achieve a wide angle and high image quality.

[0053] As described in Yoshiya Matsui's "Basics of Imaging Optics" (Japan Photonics Association, 1988, pp. 45-48), the focal length is defined as the ratio of the height of an incident ray parallel to the optical axis from infinity in the paraxial region to the angle of incidence of the ray when it exits the optical system. As defined in this document, the focal length of an optical system that forms an intermediate image (i.e., a secondary imaging system) has a negative sign.

[0054] To achieve both high performance and reduced size of the imaging optical system, the size of the entire imaging optical system can be minimized. Aberrations other than distortion also decrease in proportion to the size reduction, making it possible to achieve an imaging optical system with reduced size and high optical performance. However, in such an imaging optical system, the size of the imaging surface is also reduced, and the imaging system as a whole cannot achieve high optical performance. This is because, although a solid-state image sensor or photosensitive film is arranged on the imaging surface, the pixel density of the solid-state image sensor and the resolution per unit area of ​​the photosensitive film are technically limited. In addition, the diffraction limit determines the minimum pixel size that makes sense. Therefore, in order to achieve high image quality for the imaging system, the imaging optical system preferably has low aberrations while supporting a large imaging circle.

[0055] The imaging optical system according to each example preferably satisfies the following conditional expression (2), where La is the total length of the imaging optical system excluding the aperture stop, h is the image circle radius, and Fno is the F number of the imaging optical system.

[0056] 0.0≤La×h×Fno / f 2 ≤2.6 (2)

[0057] The total length of the imaging optical system excluding the aperture stop is the total length of the imaging optical system excluding the aperture stop in imaging optical systems that have an aperture stop or a fixed-diameter aperture used as a light-shielding mask positioned closest to the object. In other imaging optical systems, it is the total length of the imaging optical system. The total length of the imaging optical system is the distance on the optical axis from the optical surface closest to the object to the image plane. In other words, the total length of the imaging optical system excluding the aperture stop can be the distance on the optical axis from the lens surface closest to the object to the image plane.

[0058] By definition, La×h×Fno / f 2 will not become lower than the lower limit of conditional expression (2). 2When the upper limit of conditional expression (2) is exceeded, the incident angle of off-axis light on the image plane increases, the size of the exit pupil for the off-axis area decreases, and the resolution decreases due to diffraction, or the total length increases, which is not preferable. In addition, as the incident angle on the image plane increases, when a solid-state image sensor is used as an image sensor, optical crosstalk is likely to occur undesirably in the surrounding pixels.

[0059] The imaging optical system according to each example preferably satisfies the following conditional expression (3), where zp is the distance on the optical axis from the aperture stop to the image plane.

[0060] 0.1≤zp / f≤1.2 (3)

[0061] In the case where the imaging optical system does not have an aperture stop, the surface that limits the diameter of the light is the surface closest to the object, and zp is the distance on the optical axis from this surface closest to the object to the image plane. The aperture stop here is an aperture that can change the light transmission area (such as an iris stop or Waterhouse stop). The aperture stop does not necessarily need to be physically shielded and can be a type that controls the color density distribution by applying a voltage, for example, using an electrochromic element.

[0062] When zp / f becomes lower than the lower limit of conditional expression (3) and the imaging optical system has an aperture stop, the upper light rays are likely to be undesirably shielded due to the aperture stop. In the case where the imaging optical system does not have an aperture stop, the outer diameter of the lens tends to undesirably cause shielding of the upper light rays. When zp / f becomes higher than the upper limit of conditional expression (3) and the imaging optical system has an aperture stop, the lower light rays are likely to be undesirably shielded due to the aperture stop. In the case where the imaging optical system does not have an aperture stop, the lower light rays are likely to be undesirably shielded due to the outer diameter of the lens. Light shielding can be reduced by increasing the diameter of the imaging optical system, but taking such a measure will increase the size of the entire imaging optical system. This shielding of light rays has the disadvantages of reducing the amount of peripheral light and narrowing the imaging circle. In addition, since the area of ​​the exit pupil is reduced, the frequency characteristics in the meridional direction deteriorate due to diffraction phenomena and the image quality is reduced.

[0063] The imaging optical system according to each example preferably satisfies the following conditional expression (4), wherein Φm1 is the diameter of the first transflective surface, and Φm2 is the diameter of the second transflective surface. Here, "diameter" refers to the diameter of the effective area of ​​the transflective surface (the area through which effective light that contributes to imaging passes).

[0064] 0.50≤Φm1 / Φm2≤1.25 (4)

[0065] In the case where Φm1 / Φm2 becomes lower than the lower limit of conditional expression (4), the incident angle of off-axis light on the image plane increases, the size of the exit pupil for the off-axis area decreases, and the resolution decreases due to diffraction, which is not preferable. In addition, as the incident angle to the image plane increases, when a solid-state image sensor is used as an image sensor, optical crosstalk is likely to occur undesirably in the surrounding pixels. In the case where Φm1 / Φm2 becomes higher than the upper limit of conditional expression (4), the second transflective surface may block off-axis light, the size of the exit pupil for the off-axis area may decrease, and the resolution may decrease undesirably due to diffraction. In the case where Φm1 / Φm2 becomes higher than the upper limit of conditional expression (4), the size of the imaging circle decreases, and the image quality of the imaging system may deteriorate undesirably.

[0066] The imaging optical system according to each example preferably satisfies the following conditional expression (5).

[0067] 0.1≤h / (Φm2 / 2) / Fno≤1.2 (5)

[0068] In the case where h / (Φm2 / 2) / Fno becomes lower than the lower limit of conditional expression (5), the lens diameter is reduced with respect to the size of the imaging surface, and although the size of the imaging optical system is increased, it becomes undesirably difficult to improve the optical performance of the imaging system. In addition, in order to try to achieve high image quality within the possible range using a small imaging unit, the sensitivity of each surface increases, and the yield during manufacturing is reduced, which is not preferable. In the case where h / (Φm2 / 2) / Fno becomes higher than the upper limit of conditional expression (5), the incident angle of off-axis light on the image surface increases, the size of the exit pupil for the off-axis area is reduced, and the resolution is reduced due to diffraction or the total length is undesirably increased. In addition, as the incident angle on the image surface increases, when a solid-state image sensor is used as an image sensor, optical crosstalk is likely to occur undesirably in peripheral pixels.

[0069] The imaging optical system according to each example preferably satisfies the following conditional expression (6), where zm2 is the distance on the optical axis from the second transflective surface to the image plane.

[0070] 0.0≤zm2 / La≤0.5 (6)

[0071] By definition, zm2 / La does not become lower than the lower limit of conditional expression (6). In the case where zm2 / La becomes higher than the upper limit of conditional expression (6), the optical path length for folding the light decreases, and the total length increases undesirably.

[0072] The imaging optical system according to each example preferably satisfies the following conditional expression (7), where Φm1L is the absolute value of the refractive power of the lens including the second transflective surface.

[0073] 0.0≤Φm1L×f≤1.0 (7)

[0074] By definition, Φm1L×f does not become lower than the lower limit of conditional expression (7). In the case where Φm1L×f becomes higher than the upper limit of conditional expression (7), the refractive power at high ray height positions increases, which causes large longitudinal chromatic aberration and undesirably deteriorates image quality.

[0075] The imaging optical system according to each example preferably satisfies the following conditional expression (8), wherein AΦr is the average value of the absolute values ​​of the refractive powers of the plurality of lenses included in the imaging optical system, and AΦm is the average value of the absolute values ​​of the power (refractive power) of the first transflective surface and the second transflective surface. The power (reflection power) of the reflection surface corresponds to the reciprocal of the paraxial focal length of the reflection surface, and for example, if the surface is spherical, it is the reciprocal of the paraxial curvature radius multiplied by -2. Even when the reflection surface is used as a back reflector, the reflection component of the power (for example, if the shape is spherical) is the reciprocal of the paraxial curvature radius multiplied by -2, and therefore this value is used to calculate AΦr.

[0076] 0.0≤AΦr / AΦm≤0.5 (8)

[0077] In the lens disposed between the first transflective surface and the second transflective surface, light transmits through the lens three times, but when calculating AΦr, it is assumed that light transmits through the lens only once.

[0078] By definition, AΦr / AΦm will not become lower than the lower limit of conditional expression (8). In the case where AΦr / AΦm becomes higher than the upper limit of conditional expression (8), in the entire imaging optical system, the refractive power becomes more dominant than the reflective power. Essentially, the reflective surface does not produce chromatic aberration during reflection. On the other hand, the refraction of the lens causes chromatic aberration. Therefore, in the case where the refractive power in the entire system increases, longitudinal and lateral chromatic aberrations occur, and the image quality deteriorates undesirably. In addition, by satisfying conditional expression (8), chromatic aberration is less likely to occur for the above reasons, so the imaging optical system can be an optical system that can perform imaging from the visible range to the infrared range, or an optical system that can perform imaging over a wide infrared wavelength range. In this case, the quarter-wave plate or the transmissive reflective surface is preferably a quarter-wave plate or a transmissive reflective surface that can fully exert its corresponding function within the wavelength range of use.

[0079] The imaging optical system according to each example preferably satisfies the following conditional expression (9).

[0080] 0.0≤La×h / f 2 ≤2.0 (9)

[0081] By definition, La×h / f 2 will not become lower than the lower limit of conditional expression (9). 2 When the upper limit of conditional expression (9) is exceeded, the incident angle of off-axis light on the image plane increases, the size of the exit pupil for the off-axis area decreases, and the resolution decreases due to diffraction or the total length increases undesirably. When the incident angle on the image plane increases, when a solid-state image sensor is used as an image sensor, optical crosstalk is likely to occur undesirably in the surrounding pixels.

[0082] In the imaging optical systems according to each example, light loss occurs due to the first transflective surface and the second transflective surface. Therefore, when the F-number increases, the amount of light reaching the image sensor decreases. Therefore, the imaging optical systems according to each example preferably satisfy the following conditional expression (10).

[0083] 0.5≤Fno≤8.0 (10)

[0084] In the imaging optical system according to each example, one or both of the first transflective surface and the second transflective surface may not be undesirably flat. Therefore, the imaging optical system can be easily manufactured.

[0085] The numerical range in the conditional expressions (1) to (10) is preferably the range of the following conditional expressions (1a) to (10a).

[0086] 0.10≤zm1 / f≤0.67(1a)

[0087] 0.0≤La×h×Fno / f 2 ≤2.5(2a)

[0088] 0.1≤zp / f≤1.0(3a)

[0089] 0.60≤Φm1 / Φm2≤1.20(4a)

[0090] 0.1≤h / (Φm2 / 2) / Fno≤1.1(5a)

[0091] 0.00≤zm2 / La≤0.48(6a)

[0092] 0.0≤Φm1L×f≤0.7(7a)

[0093] 0.0≤AΦr / AΦm≤0.3(8a)

[0094] 0.0≤La×h / f 2 ≤1.8(9a)

[0095] 0.8≤Fno≤6.0(10a)

[0096] The numerical range in the conditional expressions (1) to (10) is preferably the range of the following conditional expressions (1b) to (10b).

[0097] 0.10≤zm1 / f≤0.65(1b)

[0098] 0.0≤La×h×Fno / f 2 ≤2.4(2b)

[0099] 0.1≤zp / f≤0.95(3b)

[0100] 0.60≤Φm1 / Φm2≤1.10(4b)

[0101] 0.1≤h / (Φm2 / 2) / Fno≤1.0(5b)

[0102] 0.00≤zm2 / La≤0.46(6b)

[0103] 0.0≤Φm1L×f≤0.5(7b)

[0104] 0.00≤AΦr / AΦm≤0.25(8b)

[0105] 0.0≤La×h / f 2 ≤1.7(9b)

[0106] 1.0≤Fno≤4.0(10b)

[0107] The numerical range in the conditional expressions (1) to (10) is preferably the range of the following conditional expressions (1c) to (10c).

[0108] 0.10≤zm1 / f≤0.55(1c)

[0109] 0.0≤La×h×Fno / f 2 ≤2.0(2c)

[0110] 0.1≤zp / f≤0.65(3c)

[0111] 0.60≤Φm1 / Φm2≤1.05(4c)

[0112] 0.1≤h / (Φm2 / 2) / Fno≤0.8(5c)

[0113] 0.00≤zm2 / La≤0.15(6c)

[0114] 0.0≤Φm1L×f≤0.35(7c)

[0115] 0.00≤AΦr / AΦm≤0.15(8c)

[0116] 0.0≤La×h / f 2 ≤1.0(9c)

[0117] 1.0≤Fno≤2.5(10c)

[0118] The first transflective surface or the second transflective surface is preferably a surface that separates incident light into reflected light and transmitted light according to the polarization state. More specifically, as described below, a polarization-selective transflective element is preferably used as the first transflective surface or the second transflective surface. Examples of polarization-selective transflective elements include those manufactured by Asahi Kasei Corporation under the product name "WGF," those manufactured by 3M under the product name "IQPE," and those manufactured by MOXTEK under the product name "ProFlux." The other transflective surface may be, for example, a half mirror. When a half mirror is used, the amount of randomly polarized light incident from the object side is reduced to less than 12.5% ​​before it reaches the image plane.

[0119] Cholesteric liquid crystals and holographic optical elements can also be used as transflective surfaces.

[0120] In the imaging optical system according to various examples, the polarization selective transflective element may be an optical element produced by forming a grid on a lens reflective surface during lens molding and then evaporating, printing, or photolithographically etching a metal or dielectric on the grid.

[0121] The shapes of the effective areas of the multiple lens surfaces included in the imaging optical system according to each example are preferably rotationally symmetric relative to the optical axis. When the imaging optical system is rotationally symmetric in the effective areas of the individual optical surfaces, the positioning of the individual optical elements can be simplified. When the imaging optical system, including the external shapes of the individual optical elements, is rotationally symmetric, manufacturing ease can be further improved.

[0122] In the imaging optical systems according to various examples, for example, the following structure can suppress a decrease in the amount of light in the normal imaging optical path while reducing ghost light (unnecessary light leakage) from the optical path that is transmitted through the transmissive reflective surface without being reflected even once.

[0123] Structure 1 using polarization

[0124] Now refer to Figure 1, a description will be given of a structure utilizing polarization. The imaging optical system using this structure has two transflective surfaces. Here, the transflective surface located on the object side of the imaging optical system using this structure is a polarization-selective transflective element (PBS): A. The transflective surface located on the image plane side of the imaging optical system using this structure is a half mirror (HM): C. A first quarter-wave plate (QWP1): B is arranged between the polarization-selective transflective element PBS and the half mirror HM. A second quarter-wave plate (QWP2): D and a linear polarizer (POL): E are arranged in order from the object side to the image side between the half mirror HM and the imaging plane IM.

[0125] Here, the polarization-selective transflective element A is configured to reflect linearly polarized light polarized in the same direction as when transmitted through the linear polarizer E, and to transmit linearly polarized light orthogonal to the linear polarizer. The polarization-selective transflective element A is, for example, a wire grid polarizer or a reflective polarizer having a laminated retardation film structure. In this case, the wire grid-forming surface or retardation film surface of the polarization-selective transflective element A serves as the transflective surface. A wire grid polarizer does not necessarily need to be a polarizer with aligned metal wires; it can be used as a polarization-selective transflective element as long as it has thin metal or dielectric layers at a specified distance. For example, an element in which the metal or dielectric layers are aligned by vapor deposition can be used.

[0126] The first quarter-wave plate B and the second quarter-wave plate D are arranged so that their slow axes are tilted 45° relative to the polarization transmission axis of the linear polarizer E. The first quarter-wave plate B and the second quarter-wave plate D are preferably arranged so that their slow axes are tilted 90°. This arrangement cancels out the wavelength dispersion characteristics of the wavelength plates when light is transmitted through the first quarter-wave plate B and the second quarter-wave plate D.

[0127] The half mirror C is a half mirror formed by, for example, dielectric multilayer film or metal deposition, and a reflective mirror surface of the half mirror C functions as a transflective surface. The linear polarizer E is, for example, an absorbing linear polarizer.

[0128] Next is a description of optical path selection and operation in the polarization-utilizing structure.

[0129] Light incident on the imaging optical system from the object side is converted into linearly polarized light by the polarization-selective transflective element A, converted into circularly polarized light by the first quarter-wave plate B, and enters the half mirror C. Part of the light reaching the half mirror C is reflected and converted into circularly polarized light in the opposite direction, and returns to the first quarter-wave plate B.

[0130] The reverse circularly polarized light that has returned to the first quarter-wave plate B is returned to the polarization selective transflective element A as linearly polarized light polarized in a direction orthogonal to the direction when the light first passed through the polarization selective transflective element A by the first quarter-wave plate B. The light that has returned to the polarization selective transflective element A is reflected by the polarization selective transflective element A. Here, due to the polarization selectivity of the polarization selective transflective element A, the linearly polarized light polarized in a direction orthogonal to the direction when the light first passed through the polarization selective transflective element A is reflected.

[0131] On the other hand, a portion of the light that has reached the half-mirror C is transmitted through the half-mirror C and becomes linearly polarized by the second quarter-wave plate D in the same direction as when the light passes through the polarization-selective transflective element A, and enters the linear polarizer E and is absorbed by the linear polarizer E.

[0132] Light reflected by the polarization-selective transflective element A is circularly polarized by the first quarter-wave plate B and enters the half-mirror C. A portion of the light reaching the half-mirror C is transmitted through the half-mirror C and enters the second quarter-wave plate D. The second quarter-wave plate D converts the incident light into linearly polarized light parallel to the linearly polarized light reflected by the polarization-selective transflective element A. The light that has passed through the second quarter-wave plate D enters the linear polarizer E. Here, the polarization of the light coincides with the transmission axis of the linear polarizer E, so most of the light is transmitted through it and guided toward the imaging plane IM.

[0133] Due to the above-described operation, only light that has transmitted through the polarization selective transflective element PBS, reflected by the half mirror C, reflected by the polarization selective transflective element PBS, and transmitted through the half mirror C is guided to the imaging plane IM.

[0134] Solid-state image sensors and charge-coupled devices (CCDs) that can be used as the imaging surface IM typically have high surface reflectivity. In this configuration, light reflected by the imaging surface IM is transmitted again through the linear polarizer E and converted into circularly polarized light by the second quarter-wave plate D. Thereafter, light emitted from the second quarter-wave plate D is reflected by the half-mirror C, becoming circularly polarized light in the opposite direction, and is transmitted again through the second quarter-wave plate D. At this point, the circularly polarized light is converted by the second quarter-wave plate D into linearly polarized light in a direction orthogonal to the direction of the light immediately before passing through the linear polarizer E. Because the direction of this linearly polarized light is orthogonal to the transmission axis of the linear polarizer E, most of the light is absorbed by the linear polarizer E. In this manner, in this configuration, most of the light reflected sequentially by the imaging surface IM and the half-mirror C is blocked, and ghosting and glare associated with the imaging surface IM are less noticeable. To achieve this reflection-reducing effect, a birefringent optical low-pass filter is preferably not present between the imaging surface IM and the linear polarizer E. This is because an optical low-pass filter causes the polarization state to shift from the desired polarization state.

[0135] In this configuration, a quarter-wave plate can be placed between the polarization-selective transflective element A and the object. In this case, the quarter-wave plate is positioned so that either its fast or slow axis forms a 45° angle with the transmission axis of the polarization-selective transflective element A. Therefore, even if the light incident from the object side is linearly polarized, imaging can be performed regardless of its polarization direction. Furthermore, a depolarizing element can be placed in place of the quarter-wave plate. For example, the "Cosmoshine SRF" from Toyobo Co., Ltd. can be used as a depolarizing element.

[0136] Structure 2 using polarization

[0137] Now refer to Figure 2 , a description will be given of a structure utilizing polarization. The imaging optical system using this structure includes two transflective surfaces. Here, the transflective surface arranged on the object side of the imaging optical system using this structure is a half mirror (HM): C. The transflective surface arranged on the imaging plane side of the imaging optical system using this structure is a polarization selective transflective element (PBS): A. A first quarter wave plate (QWP1): B is arranged between the polarization selective transflective element PBS and the half mirror HM. A linear polarizer (POL): E and a second quarter wave plate (QWP2): D are arranged between the half mirror HM and the object plane in sequence from the object side to the image side.

[0138] Here, the structure of each polarization element and the preferred arrangement of the optical axis orientation are the same as those of Structure 1 utilizing polarization.

[0139] What follows is a description of optical path selection and operation in a structure utilizing polarization.

[0140] Light entering the imaging optical system from the object side is converted into linearly polarized light by the linear polarizer E, converted into circularly polarized light by the second quarter-wave plate D, and enters the half mirror C. Part of the light reaching the half mirror C is reflected and converted into circularly polarized light in the opposite direction, and returns to the second quarter-wave plate D.

[0141] The light that has reached and reflected the half mirror C becomes circularly polarized light in the direction opposite to that when incident. This light is converted by the second quarter-wave plate D into linearly polarized light in a direction orthogonal to the direction when passing through the linear polarizer E, enters the linear polarizer E, and is absorbed by it.

[0142] On the other hand, the light that has been transmitted through the half mirror C is converted by the first quarter wave plate B into linearly polarized light in the same direction as the light polarized immediately after being transmitted through the linear polarizer E. This linearly polarized light is reflected by the polarization-selective transflective element A and returns to the first quarter wave plate B. Thereafter, the light is converted into circularly polarized light by the first quarter wave plate B, and a portion of the light is reflected by the half mirror C. The light reflected by the half mirror C enters the first quarter wave plate B again and is converted into linearly polarized light whose polarization direction is orthogonal to the polarization direction when reflected by the polarization-selective transflective element A. This linearly polarized light is transmitted through the polarization-selective transflective element A and is guided to the imaging surface IM.

[0143] Due to the above-described operation, only light that has transmitted through the half mirror C, reflected by the polarization selective transflective element PBS, reflected by the half mirror C, and transmitted through the polarization selective transflective element PBS is guided to the imaging plane IM.

[0144] In this arrangement, a linear polarizer A' can be disposed between the polarization-selective transflective element A and the imaging surface IM. In this case, the transmission axes of the linear polarizer A' and the polarization-selective transflective element A coincide with each other. Therefore, light that is reflected by the imaging surface IM, further reflected by the polarization-selective transflective element A, and then re-enters the imaging surface IM to cause ghost images and flare can be absorbed.

[0145] In this configuration, a quarter-wave plate can be placed between the linear polarizer E and the object. In this case, the quarter-wave plate is positioned so that its fast or slow axis forms a 45° angle with the transmission axis of the linear polarizer E. Therefore, even if the light incident from the object side is linearly polarized, imaging can be performed regardless of its polarization direction. A depolarizing element can be used in place of the quarter-wave plate. For example, the "Cosmoshine SRF" from Toyobo Co., Ltd. can be used as a depolarizing element.

[0146] In the above description of the structure, terms such as orthogonal, parallel, and 45° are used, but they do not have to be strictly 90°, 0°, and 45°. However, they should be within ±5° of the set angle, preferably within ±2°, or more preferably within ±1°.

[0147] In the imaging optical system according to various examples, the lens may be made of a polymer material or a glass material. However, the lens disposed between the first transflective surface and the second transflective surface may have low birefringence.

[0148] In the above two structures, the quarter-wave plate can be, for example, a polymer film such as "WA-140T" manufactured by Nippon Kayaku Co., Ltd., "CP3" manufactured by ColorLink Japan Co., Ltd., or "ZEONORFILM" manufactured by Zeon Co., Ltd. In addition, for example, products named "APAW", "APSAW-5", and "APSAW-7" by Astropribor and products named "Super Achromatic Waveplate" (models: SAQWP05M-700, SAQWP05M-1700, etc.) and "Achromatic Waveplate" (models: AQWP05M-600, AQWP05M-580, AQWP10M-580, etc.) by Thorlabs can be used.

[0149] Regarding the quarter-wave plate placed between two transmissive reflective surfaces, if its characteristics are insufficient (i.e., it deviates from the ideal characteristics of providing only a quarter-wavelength of retardation and provides too large or too small a phase difference, or has a component that acts as a depolarizer or optical rotator), ghost flare increases. More specifically, for example, if the phase difference deviates from a quarter-wavelength, light reflected twice by each of the two transmissive reflective surfaces will reach the image plane as ghost flare. For light incident on the optical axis, when the phase difference provided by the quarter-wave plate is δ (degrees), the intensity of the ghost light is expressed as {(1-cos(2δ))^2}×(1+cos(2δ))×a / 64 (where a is a constant that summarizes the absorption, reflection, and other elements of each lens in the optical system). The calculations here assume the ideal characteristics of the polarizer (i.e., it absorbs all polarized light in the absorption axis direction and transmits all polarized light in the transmission axis direction). This ghost light is temporarily referred to as five-pass ghost.

[0150] Since the amount of light on the normal optical path explained in the above structural description (which can be an optical path through which light can be transmitted in this manner) is (1-cos(2δ))^2}×a / 16, the ratio of the light amounts of normal light and the five-way ghost optical path is 4 / (1+cos(2δ)). Therefore, when the phase difference provided by the quarter-wave plate deviates from 90°, the light amount of the five-way ghost rapidly increases relative to the normal light, and strong ghosting occurs.

[0151] Therefore, in the used wavelength band (mainly used wavelength band), the following conditional expressions (11a) and (12a) can be satisfied, where a22 is a 2×2 element of the Mueller matrix corresponding to the quarter-wave plate configured between the two transmission and reflection surfaces, and a32 is a 3×2 element of the Mueller matrix.

[0152] -0.25≤a22≤0.25(11a)

[0153] -0.25≤a32≤0.25(12a)

[0154] Therefore, five-way ghosting can be fully suppressed. The Mueller matrix is ​​the matrix when observing the quarter-wave plate from the incident side with linearly polarized light perpendicularly incident on it. It is expressed when the angle between the axis corresponding to the fast axis (or slow axis) and the incident polarized light is 45°. The wavelength range used primarily is the area where the light receiver, such as an image sensor or photosensitive film, has sufficient sensitivity and where reflection and absorption in the optical system are sufficiently low. In addition, when the wavelength of the incident light is limited, the spectral spectrum of the incident light is also considered. More specifically, the wavelength range to be used is the area where the product of the light receiver sensitivity, the efficiency of the optical system, and the spectrum of the incident light is at least 10% or 20% of the peak value.

[0155] Conditional expressions (11a) and (12a) are preferably replaced by the following conditional expressions (11b) and (12b), or more preferably by the following conditional expressions (11c) and (12c), or most preferably by the following conditional expressions (11d) and (12d).

[0156] -0.20≤a22≤0.20(11b)

[0157] -0.20≤a32≤0.20(12b)

[0158] -0.10≤a22≤0.10(11c)

[0159] -0.10≤a32≤0.10(12c)

[0160] -0.05≤a22≤0.05(11d)

[0161] -0.05≤a32≤0.05(12d)

[0162] Examples of quarter-wave plate structures that satisfy these conditional expressions over the entire visible range (e.g., 420 nm to 680 nm) can include an HQ-type quarter-wave plate made by stacking a half-wave plate whose optical axis is tilted by approximately 15° relative to the incident polarization direction, a quarter-wave plate whose optical axis is tilted by approximately 75°, and a Pancharatnam-type quarter-wave plate that combines two half-wave plates and one quarter-wave plate at predetermined angles (such as typically with the optical axis at 6.5°, 34.57°, and 101.13° relative to the incident polarization direction), and they are preferably used in the present invention.

[0163] The above-mentioned "CP3", "APSAW-5", "APSAW-7" and "Super Achromatic Wave Plate" are such Pancharatnam type wave plates.

[0164] A quarter wave plate having characteristics close to those of the above wave plate is preferably used for the other quarter wave plate (ie, Figure 1 and Figure 2 (D in FIG). Each of the two quarter-wave plates acts on light that has not been reflected even once by the two transmissive reflective surfaces to cancel it out, thereby preventing the light from reaching the image plane. Therefore, the characteristics of the two quarter-wave plates are preferably as nearly identical as possible, so that the cancellation of the characteristics is almost complete.

[0165] The optical system according to each example can be an optical system that does not form an intermediate image (i.e., a primary imaging system). In a primary imaging system, an image plane is formed at the location where the incident light is first focused. This structure can reduce the overall length of the optical system. Compared to an optical system that forms an intermediate image (i.e., a secondary imaging system), a primary imaging system does not require the focal length of each lens to be increased, and therefore can more easily correct aberrations than using a secondary imaging system.

[0166] The structures of imaging optical systems according to various examples will be described below.

[0167] Example 1

[0168] Will refer to Figure 3 An imaging optical system 100 according to Example 1 is described. Figure 3 : is a cross-sectional view of the imaging optical system 100. The imaging optical system 100 includes, in order from the object side to the image side, a first lens 101 having a first transflective surface HM1, a second lens 102, a third lens 103 having a second transflective surface HM2, and a sensor protection glass GB. The first lens 101 has a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0169] Figure 4 1 and 2 are aberration diagrams when the imaging optical system 100 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0170] This imaging optical system 100 performs focusing by moving a first lens 101 , a second lens 102 , and a third lens 103 as an integrated unit in the optical axis direction.

[0171] Example 2

[0172] Will refer to Figure 5 An imaging optical system 200 according to Example 2 is described. Figure 52 is a cross-sectional view of an imaging optical system 200. The imaging optical system 200 includes, in order from the object side to the image side, a first lens 201 having a first transflective surface HM1, a second lens 202, a third lens 203 having a second transflective surface HM2, and sensor protection glass GB. The first lens 201 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0173] Figure 6 1 and 2 are aberration diagrams when the imaging optical system 200 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0174] This imaging optical system 200 performs focusing by moving a first lens 201 , a second lens 202 , and a third lens 203 as an integrated unit in the optical axis direction.

[0175] Example 3

[0176] Will refer to Figure 7 An imaging optical system 300 according to Example 3 is described. Figure 7 : is a cross-sectional view of the imaging optical system 300. The imaging optical system 300 includes, in order from the object side to the image side, a first lens 301, an aperture stop SP, a second lens 302 having a first transflective surface HM1, a third lens 303, a fourth lens 304 having a second transflective surface HM2, and a sensor protection glass GB. The second lens 302 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0177] Figure 8 1 and 2 are aberration diagrams when the imaging optical system 300 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0178] This imaging optical system 300 performs focusing by moving a first lens 301 , a second lens 302 , a third lens 303 , and a fourth lens 304 as an integrated unit in the optical axis direction.

[0179] Example 4

[0180] Will refer to Figure 9 An imaging optical system 400 according to Example 4 is described. Figure 9 : is a cross-sectional view of an imaging optical system 400. The imaging optical system 400 includes, in order from the object side to the image side, a first lens 401, an aperture stop SP, a second lens 402 having a first transflective surface HM1, a third lens 403, a fourth lens 404 having a second transflective surface HM2, and a sensor protection glass GB. The second lens 402 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0181] Figure 10 4 are aberration diagrams when the imaging optical system 400 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0182] This imaging optical system 400 performs focusing by moving a first lens 401 , a second lens 402 , a third lens 403 , and a fourth lens 404 as an integrated unit in the optical axis direction.

[0183] Example 5

[0184] Will refer to Figure 11 An imaging optical system 500 according to Example 5 is described. Figure 11 : is a cross-sectional view of an imaging optical system 500. The imaging optical system 500 includes, in order from the object side to the image side, a first lens 501, an aperture stop SP, a second lens 502 having a first transflective surface HM1, a third lens 503, a fourth lens 504 having a second transflective surface HM2, and sensor protection glass GB. The second lens 502 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0185] Figure 12 Aberration diagrams are shown when the imaging optical system 500 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0186] This imaging optical system 500 performs focusing by moving a first lens 501 , a second lens 502 , a third lens 503 , and a fourth lens 504 as an integrated unit in the optical axis direction.

[0187] Example 6

[0188] Will refer to Figure 13 An imaging optical system 600 according to Example 6 is described. Figure 13 : is a cross-sectional view of an imaging optical system 600. The imaging optical system 600 includes, in order from the object side to the image side, a first lens 601, an aperture stop SP, a second lens 602, a third lens 603 having a first transflective surface HM1, a fourth lens 604, a fifth lens 605 having a second transflective surface HM2, and sensor protection glass GB. The third lens 603 further includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0189] Figure 14 1 and 2 are aberration diagrams when the imaging optical system 600 is in a focused state at infinity at wavelengths for the d-line, F-line, C-line, and g-line.

[0190] This imaging optical system 600 performs focusing by moving a first lens 601 , a second lens 602 , a third lens 603 , a fourth lens 604 , and a fifth lens 605 as an integrated unit in the optical axis direction.

[0191] Example 7

[0192] Will refer to Figure 15 An imaging optical system 700 according to Example 7 is described. Figure 15 : is a cross-sectional view of an imaging optical system 700. The imaging optical system 700 includes, in order from the object side to the image side, a first lens 701 having a first transflective surface HM1, a second lens 702, a third lens 703 having a second transflective surface HM2, and sensor protection glass GB. The first lens 701 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0193] Figure 16 1 and 2 are aberration diagrams when the imaging optical system 700 is in a focused state at infinity at wavelengths for the d-line, F-line, C-line, and g-line.

[0194] This imaging optical system 700 performs focusing by moving a first lens 701, a second lens 702, and a third lens 703 as an integrated unit in the optical axis direction. Focusing can also be performed by moving the third lens 703.

[0195] Example 8

[0196] Will refer to Figure 17 An imaging optical system 800 according to Example 8 is described. Figure 17 : This is a cross-sectional view of an imaging optical system 800. The imaging optical system 800 includes, in order from the object side to the image side, a cemented lens integrating a first lens 801 having a first transflective surface HM1 and a second lens 802, a third lens 803, a fourth lens 804 having a second transflective surface HM2, and sensor protection glass GB. The first lens 801 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0197] Figure 18 1 and 2 are aberration diagrams when the imaging optical system 800 is in a focused state at infinity at wavelengths for the d-line, F-line, C-line, and g-line.

[0198] This imaging optical system 800 performs focusing by moving a first lens 801 , a second lens 802 , a third lens 803 , and a fourth lens 804 as an integrated unit in the optical axis direction.

[0199] Example 9

[0200] Will refer to Figure 19An imaging optical system 900 according to Example 9 is described. Figure 19 : is a cross-sectional view of an imaging optical system 900. The imaging optical system 900 includes, in order from the object side to the image side, a first lens 901, a second lens 902 having a first transflective surface HM1, a third lens 903, an aperture stop SP, and a fourth lens 904 having a second transflective surface HM2. The second lens 902 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0201] Figure 20 1 and 2 are aberration diagrams when the imaging optical system 900 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0202] This imaging optical system 900 performs focusing by moving a first lens 901 , a second lens 902 , a third lens 903 , and a fourth lens 904 as an integrated unit in the optical axis direction.

[0203] Example 10

[0204] Will refer to Figure 21 An imaging optical system 1000 according to Example 10 is described. Figure 21 1 is a cross-sectional view of an imaging optical system 1000. The imaging optical system 1000 includes, in order from the object side to the image side, a first lens 1001 having a first transflective surface HM1, an aperture stop SP, a second lens 1002, and a third lens 1003 having a second transflective surface HM2. The first lens 1001 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0205] Figure 22 1 and 2 are aberration diagrams when the imaging optical system 1000 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0206] This imaging optical system 1000 performs focusing by moving a first lens 1001 , a second lens 1002 , and a third lens 1003 as an integrated unit in the optical axis direction.

[0207] Example 11

[0208] Will refer to Figure 23 An imaging optical system 1100 according to Example 11 is described. Figure 23 1 is a cross-sectional view of an imaging optical system 1100. The imaging optical system 1100 includes, in order from the object side to the image side, a first lens 1101 having a first transflective surface HM1, an aperture stop SP, a second lens 1102 having a second transflective surface HM2, and a sensor protection glass GB. The first lens 1101 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0209] Figure 24 Aberration diagrams are shown when the imaging optical system 1100 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0210] This imaging optical system 1100 performs focusing by moving a first lens 1101 and a second lens 1102 as an integrated unit in the optical axis direction.

[0211] Example 12

[0212] Will refer to Figure 25 An imaging optical system 1200 according to Example 12 is described. Figure 25 1 is a cross-sectional view of an imaging optical system 1200. The imaging optical system 1200 includes, in order from the object side to the image side, a first lens 1201, a second lens 1202 having a first transflective surface HM1, an aperture stop SP, a third lens 1203, and a fourth lens 1204 having a second transflective surface HM2. The second lens 1202 includes a quarter-wave plate QWP on the image side of the first transflective surface HM1.

[0213] Figure 26 Aberration diagrams are shown when the imaging optical system 1200 is in a focused state at infinity at the wavelengths of the d-line, F-line, C-line, and g-line.

[0214] This imaging optical system 1200 performs focusing by moving a first lens 1201 , a second lens 1202 , a third lens 1203 , and a fourth lens 1204 as an integrated unit in the optical axis direction.

[0215] Numerical Examples 1 to 12 corresponding to Examples 1 to 12, respectively, are shown below. In the surface data of each numerical example, the surface number i indicates the i-th surface along the optical path counted from the object side. r represents the radius of curvature of the i-th surface (mm), d represents the lens thickness or air space (mm) between the i-th and (i+1)-th surfaces, and nd is the refractive index of the material of the i-th optical component for the d-line. νd is the Abbe number of the material of the i-th optical component based on the d-line. The Abbe number νd is expressed as:

[0216] νd=(Nd-1) / (NF-NC)

[0217] 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) in the Fraunhofer line. For regions where the medium is air, the refractive index and Abbe number are omitted.

[0218] An asterisk "*" following a surface number means that the surface has an aspherical shape. The aspherical shape is expressed by the following equation, where x is the displacement of the surface vertex in the direction of the optical axis at a height h relative to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and Ai (i = 2, 4, 6, 8, ...) is the aspherical coefficient of each order.

[0219]

[0220] Each of the first transflective surface and the second transflective surface has an effective diameter, and although these transflective surfaces act on the light multiple times, the diameter having the largest effective diameter among them is provided.

[0221] Various data also indicate focal length (mm), F number, half angle of view (°), image height (mm), etc. The total lens length here refers to the total length of the optical path before and after reflection by the optical surface. The "distance on the optical axis" in each of the above conditional expressions does not show the optical path length including the reflected optical path, but rather shows the physical distance on the optical axis.

[0222] Numerical Example 1

[0223] Unit: mm

[0224] Polygon data

[0225]

[0226] Aspheric surface data

[0227] Page 1

[0228] K=0.00000e+00A2=2.93156e-02A4=-2.44711e-04A6=-9.53633e-05A8=3.71660e-07

[0229] Page 2

[0230] K=0.00000e+00A4=-1.19829e-03A6=-1.21820e-04A8=6.09483e-06A10=-1.20923e-07

[0231] Page 3

[0232] K=0.00000e+00A4=-4.35935e-03A6=-6.60834e-05A8=-1.18728e-06A10=1.31629e-06A12=-4.73569e-08Page 4

[0233] K=0.00000e+00A4=-3.41190e-03A6=1.89881e-05A8=-2.44660e-06A10=6.47853e-07

[0234] Page 5

[0235] K=0.00000e+00A4=1.93169e-05A6=-1.00030e-05A8=4.60648e-06A10=-4.74183e-07A12=8.23996e-09Page 6

[0236] K=0.00000e+00A4=-3.41190e-03A6=1.89881e-05A8=-2.44660e-06A10=6.47853e-07

[0237] Page 7

[0238] K=0.00000e+00A4=-4.35935e-03A6=-6.60834e-05A8=-1.18728e-06A10=1.31629e-06A12=-4.73569e-08Page 8

[0239] K=0.00000e+00A4=-1.19829e-03A6=-1.21820e-04A8=6.09483e-06A10=-1.20923e-07

[0240] Page 9

[0241] K=0.00000e+00A4=-4.35935e-03A6=-6.60834e-05A8=-1.18728e-06A10=1.31629e-06A12=-4.73569e-08Page 10

[0242] K=0.00000e+00A4=-3.41190e-03A6=1.89881e-05A8=-2.44660e-06A10=6.47853e-07

[0243] Page 11

[0244] K=0.00000e+00A4=1.93169e-05A6=-1.00030e-05A8=4.60648e-06A10=-4.74183e-07A12=8.23996e-09 Page 12

[0245] K=0.00000e+00A2=-6.31717e-02A4=-2.01465e-02A6=3.87149e-03A8=-2.23890e-04

[0246] Various data

[0247]

[0248] Single lens data

[0249]

[0250]

[0251] Numerical example 2 Unit: mm Surface data

[0252] Aspheric surface data: Surface 1: K = 0.00000e + 00A2 = 6.44766e - 03A4 = -2.00927e - 03A6 = -3.97094e - 05A8 = -3.63375e -10

[0253] Page 2

[0254] K=0.00000e+00A2=5.44285e-03A4=-1.31498e-03A6=-5.55271e-05A8=1.13341e-06A10=-1.84643e-08Page 3

[0255] K=0.00000e+00A4=7.82567e-04A6=-1.40770e-04A8=3.13547e-06A10=-1.31494e-07A12=3.12347e-10Page 4

[0256] K=0.00000e+00A4=3.11322e-04A6=-1.02677e-04A8=1.74990e-06A10=-1.75766e-08

[0257] Page 5

[0258] K=0.00000e+00A2=-2.02253e-02A4=-1.15206e-04A6=-2.11799e-06A8=5.06262e-07A10=-3.28619e-08A12=5.43529e-10

[0259] Page 6

[0260] K=0.00000e+00A4=3.11322e-04A6=-1.02677e-04A8=1.74990e-06A10=-1.75766e-08

[0261] Page 7

[0262] K=0.00000e+00A4=7.82567e-04A6=-1.40770e-04A8=3.13547e-06A10=-1.31494e-07A12=3.12347e-10Page 8

[0263] K=0.00000e+00A2=5.44285e-03A4=-1.31498e-03A6=-5.55271e-05A8=1.13341e-06A10=-1.84643e-08Page 9

[0264] K=0.00000e+00A4=7.82567e-04A6=-1.40770e-04A8=3.13547e-06A10=-1.31494e-07A12=3.12347e-10 Page 10

[0265] K=0.00000e+00A4=3.11322e-04A6=-1.02677e-04A8=1.74990e-06A10=-1.75766e-08

[0266] Page 11

[0267] K=0.00000e+00A2=-2.02253e-02A4=-1.15206e-04A6=-2.11799e-06A8=5.06262e-07A10=-3.28619e-08A12=5.43529e-10

[0268] Page 12

[0269] K=0.00000e+00A2=-2.14048e-01A4=-5.68547e-03A6=1.10815e-03A8=-1.66701e-04

[0270] Various data

[0271]

[0272] Single lens data

[0273] Numerical example 3 Unit: mm surface data

[0274]

[0275] Aspheric surface data

[0276] Page 1

[0277] K=0.00000e+00A2=-9.35147e-02A4=-7.52625e-03A6=-2.21557e-04A8=1.07810e-05

[0278] Page 2

[0279] K=0.00000e+00A4=-5.74115e-03A6=-8.84359e-05A8=1.76716e-05

[0280] Page 4

[0281] K=0.00000e+00A4=4.10588e-04A6=-4.73325e-05A8=4.02713e-06

[0282] Page 6

[0283] K=0.00000e+00A4=-1.03372e-03A6=2.09064e-04A8=2.54380e-06A10=-9.43289e-08A12=-4.31995e-09Page 7

[0284] K=0.00000e+00A4=-5.62087e-04A6=1.60507e-04A8=8.13802e-07A10=-1.76377e-09

[0285] Page 9

[0286] K=0.00000e+00A4=-5.62087e-04A6=1.60507e-04A8=8.13802e-07A10=-1.76377e-09

[0287] Page 10

[0288] K=0.00000e+00A4=-1.03372e-03A6=2.09064e-04A8=2.54380e-06A10=-9.43289e-08A12=-4.31995e-09Page 12

[0289] K=0.00000e+00A4=-1.03372e-03A6=2.09064e-04A8=2.54380e-06A10=-9.43289e-08A12=-4.31995e-09Page 13

[0290] K=0.00000e+00A4=-5.62087e-04A6=1.60507e-04A8=8.13802e-07A10=-1.76377e-09

[0291] Various data

[0292]

[0293] Single lens data

[0294]

[0295] Numerical example 4 Unit: mm surface data

[0296]

[0297] Aspheric surface data

[0298] Page 1

[0299] K=0.00000e+00A2=5.83310e-02A4=-4.68852e-03A6=-7.18937e-04A8=5.20323e-05

[0300] Page 2

[0301] K=0.00000e+00A4=-3.80340e-03A6=-8.66114e-04A8=8.49003e-05

[0302] Page 4

[0303] K=0.00000e+00A4=2.52338e-03A6=-2.59547e-04A8=1.40104e-05

[0304] Page 5

[0305] K=0.00000e+00A4=-4.92829e-04A6=-3.13893e-05A8=-3.08591e-06A10=-5.51250e-07

[0306] Page 6

[0307] K=0.00000e+00A4=-6.93674e-03A6=6.41759e-04A8=-9.88404e-05A10=1.12955e-05A12=-2.96339e-07Page 7

[0308] K=0.00000e+00A4=-5.75763e-03A6=6.07633e-04A8=-7.35934e-05A10=5.38917e-06

[0309] Page 8

[0310] K=0.00000e+00A4=2.32593e-04A6=-4.77838e-05A8=4.51163e-06A10=2.68794e-07A12=-4.53602e-08Page 9

[0311] K=0.00000e+00A4=-5.75763e-03A6=6.07633e-04A8=-7.35934e-05A10=5.38917e-06

[0312] Page 10

[0313] K=0.00000e+00A4=-6.93674e-03A6=6.41759e-04A8=-9.88404e-05A10=1.12955e-05A12=-2.96339e-07 Page 11

[0314] K=0.00000e+00A4=-4.92829e-04A6=-3.13893e-05A8=-3.08591e-06A10=-5.51250e-07

[0315] Page 12

[0316] K=0.00000e+00A4=-6.93674e-03A6=6.41759e-04A8=-9.88404e-05A10=1.12955e-05A12=-2.96339e-07 Page 13

[0317] K=0.00000e+00A4=-5.75763e-03A6=6.07633e-04A8=-7.35934e-05A10=5.38917e-06

[0318] Page 14

[0319] K=0.00000e+00A4=2.32593e-04A6=-4.77838e-05A8=4.51163e-06A10=2.68794e-07A12=-4.53602e-08Page 15

[0320] K=0.00000e+00A2=5.07013e-02A4=9.71519e-03A6=-5.83288e-04A8=2.09748e-05

[0321] Various data

[0322]

[0323]

[0324] Single lens data

[0325] Numerical example 5 Unit: mm surface data

[0326] Aspheric surface data

[0327] Page 1

[0328] K=0.00000e+00A2=-7.03524e-02A4=-1.39437e-02A6=-9.52179e-04A8=-3.90902e-05A10=2.66067e-06A12=1.31574e-08

[0329] Page 2

[0330] K=0.00000e+00A4=-1.49638e-02A6=-8.77799e-04A8=1.03612e-04A10=-1.00467e-05A12=7.47849e-07Page 4

[0331] K=0.00000e+00A4=-6.80839e-03A6=4.69122e-04A8=8.21024e-05

[0332] Page 5

[0333] K=0.00000e+00A4=-2.32860e-03A6=2.20307e-04A8=4.54969e-06A10=-5.17761e-07

[0334] Page 6

[0335] K=0.00000e+00A4=8.72885e-03A6=-6.45244e-04A8=-2.44843e-05A10=5.63144e-06A12=-1.87955e-07Page 7

[0336] K=0.00000e+00A4=5.50577e-03A6=-2.62192e-04A8=-1.37424e-05A10=1.11199e-06

[0337] Page 8

[0338] K=0.00000e+00A4=-3.18341e-05A6=1.78016e-05A8=-4.11465e-06A10=6.26657e-07A12=-1.73006e-08Page 9

[0339] K=0.00000e+00A4=5.50577e-03A6=-2.62192e-04A8=-1.37424e-05A10=1.11199e-06

[0340] Page 10

[0341] K=0.00000e+00A4=8.72885e-03A6=-6.45244e-04A8=-2.44843e-05A10=5.63144e-06A12=-1.87955e-07 Page 11

[0342] K=0.00000e+00A4=-2.32860e-03A6=2.20307e-04A8=4.54969e-06A10=-5.17761e-07

[0343] Page 12

[0344] K=0.00000e+00A4=8.72885e-03A6=-6.45244e-04A8=-2.44843e-05A10=5.63144e-06A12=-1.87955e-07 Page 13

[0345] K=0.00000e+00A4=5.50577e-03A6=-2.62192e-04A8=-1.37424e-05A10=1.11199e-06

[0346] Page 14

[0347] K=0.00000e+00A4=-3.18341e-05A6=1.78016e-05A8=-4.11465e-06A10=6.26657e-07A12=-1.73006e-08Page 15

[0348] K=0.00000e+00A2=5.50201e-02A4=9.90886e-03A6=-5.77224e-04A8=1.23735e-05

[0349] Various data

[0350]

[0351] Zoom lens unit data

[0352] Lens unit starting surface focal length Lens composition length Front principal point position Rear principal point position 1 1 6.20 5.40-0.11-6.10 Single lens data

[0353]

[0354] Numerical Example 6

[0355] Unit: mm

[0356] Polygon data

[0357]

[0358]

[0359] Aspheric surface data

[0360] Page 1

[0361] K=0.00000e+00A2=-2.76193e-02A4=-1.48482e-04A6=-3.44041e-07A8=4.05757e-09A10=-1.32702e-10A12=7.47796e-13

[0362] Page 2

[0363] K=0.00000e+00A4=2.35488e-04A6=5.10752e-06A8=-5.19375e-08A10=4.95941e-09A12=-8.12477e-11Page 4

[0364] K=0.00000e+00A4=-1.40363e-03A6=-2.20005e-07A8=-7.57564e-07A10=2.69338e-08

[0365] Page 5

[0366] K=0.00000e+00A4=-8.83456e-04A6=6.59973e-06A8=-6.72884e-07

[0367] Page 6

[0368] K=0.00000e+00A4=-8.94061e-04A6=6.01317e-06A8=-1.92247e-06

[0369] Page 7

[0370] K=0.00000e+00A4=-4.09096e-04A6=2.80743e-06A8=-2.80466e-07A10=1.11480e-08

[0371] Page 8

[0372] K=0.00000e+00A4=2.59434e-04A6=-2.40538e-05A8=8.94418e-07A10=-1.99380e-08A12=9.77907e-11Page 9

[0373] K=0.00000e+00A4=1.36420e-04A6=-2.18568e-05A8=7.88464e-07A10=-1.32052e-08

[0374] Page 10

[0375] K=0.00000e+00A4=-6.16694e-05A6=3.13305e-06A8=-9.19933e-08A10=-9.29122e-10A12=5.19478e-11 Page 11

[0376] K=0.00000e+00A4=1.36420e-04A6=-2.18568e-05A8=7.88464e-07A10=-1.32052e-08

[0377] Page 12

[0378] K=0.00000e+00A4=2.59434e-04A6=-2.40538e-05A8=8.94418e-07A10=-1.99380e-08A12=9.77907e-11 Page 13

[0379] K=0.00000e+00A4=-4.09096e-04A6=2.80743e-06A8=-2.80466e-07A10=1.11480e-08

[0380] Page 14

[0381] K=0.00000e+00A4=2.59434e-04A6=-2.40538e-05A8=8.94418e-07A10=-1.99380e-08A12=9.77907e-11 Page 15

[0382] K=0.00000e+00A4=1.36420e-04A6=-2.18568e-05A8=7.88464e-07A10=-1.32052e-08

[0383] Page 16

[0384] K=0.00000e+00A4=-6.16694e-05A6=3.13305e-06A8=-9.19933e-08A10=-9.29122e-10A12=5.19478e-11 Page 17

[0385] K=0.00000e+00A2=2.20836e-02A4=1.76117e-03A6=-3.85080e-05A8=1.93218e-07

[0386] Various data

[0387]

[0388] Single lens data

[0389] Numerical example 7 Unit: mm surface data

[0390]

[0391] Aspheric surface data

[0392] Page 1

[0393] K=0.00000e+00A2=-7.91546e-02A4=-1.36693e-03A6=-2.46324e-05A8=-2.09970e-06

[0394] Page 2

[0395] K=0.00000e+00A4=-1.07656e-03A6=-3.90324e-05A8=-6.35705e-07A10=-4.59773e-08

[0396] Page 3

[0397] K=0.00000e+00A4=-2.72817e-03A6=-4.29541e-04A8=5.58439e-06A10=9.86298e-07A12=-8.89788e-08Page 4

[0398] K=0.00000e+00A4=-1.98197e-03A6=-5.38358e-04A8=7.88237e-06A10=2.92046e-07

[0399] Page 5

[0400] K=0.00000e+00A2=-4.96450e-02A4=6.33648e-04A6=5.09842e-05A8=-1.67185e-05A10=-9.37608e-07A12=7.64872e-08

[0401] Page 6

[0402] K=0.00000e+00A4=-4.16257e-05A6=3.80574e-05A8=-3.61205e-06

[0403] Page 7

[0404] K=0.00000e+00A2=-4.96450e-02A4=6.33648e-04A6=5.09842e-05A8=-1.67185e-05A10=-9.37608e-07A12=7.64872e-08

[0405] Page 8

[0406] K=0.00000e+00A4=-1.98197e-03A6=-5.38358e-04A8=7.88237e-06A10=2.92046e-07

[0407] Page 9

[0408] K=0.00000e+00A4=-2.72817e-03A6=-4.29541e-04A8=5.58439e-06A10=9.86298e-07A12=-8.89788e-08Page 10

[0409] K=0.00000e+00A4=-1.07656e-03A6=-3.90324e-05A8=-6.35705e-07A10=-4.59773e-08

[0410] Page 11

[0411] K=0.00000e+00A4=-2.72817e-03A6=-4.29541e-04A8=5.58439e-06A10=9.86298e-07A12=-8.89788e-08Page 12

[0412] K=0.00000e+00A4=-1.98197e-03A6=-5.38358e-04A8=7.88237e-06A10=2.92046e-07

[0413] Page 13

[0414] K=0.00000e+00A2=-4.96450e-02A4=6.33648e-04A6=5.09842e-05A8=-1.67185e-05A10=-9.37608e-07A12=7.64872e-08

[0415] Page 14

[0416] K=0.00000e+00A4=-4.16257e-05A6=3.80574e-05A8=-3.61205e-06 Various data

[0417] Single lens data

[0418]

[0419] Numerical example 8 Unit: mm surface data

[0420] Aspheric surface data 1

[0421] K=0.00000e+00A2=2.78605e-03A4=-7.25744e-04A6=-7.51303e-07A8=-1.74988e-07

[0422] Page 2

[0423] K=0.00000e+00A4=-1.43237e-03A6=-4.13680e-05A8=-8.70457e-06A10=5.72952e-07

[0424] Page 3

[0425] K=0.00000e+00A2=-1.04474e-01A4=-1.19801e-03A6=2.88680e-05A8=-1.49038e-06A10=1.78478e-08Page 4

[0426] K=0.00000e+00A4=-3.80060e-03A6=2.50706e-04A8=-1.42146e-05A10=2.21897e-07A12=9.88712e-10Page 5

[0427] K=0.00000e+00A4=-3.70781e-03A6=1.97247e-04A8=-9.83150e-06A10=1.76891e-07

[0428] Page 6

[0429] K=0.00000e+00A4=-5.34069e-05A6=2.02098e-05A8=-2.25255e-06A10=1.01424e-07A12=-1.76046e-09Page 7

[0430] K=0.00000e+00A4=-3.70781e-03A6=1.97247e-04A8=-9.83150e-06A10=1.76891e-07

[0431] Page 8

[0432] K=0.00000e+00A4=-3.80060e-03A6=2.50706e-04A8=-1.42146e-05A10=2.21897e-07A12=9.88712e-10Page 9

[0433] K=0.00000e+00A2=-1.04474e-01A4=-1.19801e-03A6=2.88680e-05A8=-1.49038e-06A10=1.78478e-08Page 10

[0434] K=0.00000e+00A4=-1.43237e-03A6=-4.13680e-05A8=-8.70457e-06A10=5.72952e-07

[0435] Page 11

[0436] K=0.00000e+00A2=-1.04474e-01A4=-1.19801e-03A6=2.88680e-05A8=-1.49038e-06A10=1.78478e-08Page 12

[0437] K=0.00000e+00A4=-3.80060e-03A6=2.50706e-04A8=-1.42146e-05A10=2.21897e-07A12=9.88712e-10 Page 13

[0438] K=0.00000e+00A4=-3.70781e-03A6=1.97247e-04A8=-9.83150e-06A10=1.76891e-07

[0439] Page 14

[0440] K=0.00000e+00A4=-5.34069e-05A6=2.02098e-05A8=-2.25255e-06A10=1.01424e-07A12=-1.76046e-09Page 15

[0441] K=0.00000e+00A2=-2.31030e-01A4=-2.51324e-03A6=4.11608e-04A8=-7.78731e-05

[0442] Various data

[0443]

[0444]

[0445] Single lens data

[0446] Numerical example 9 Unit: mm surface data

[0447]

[0448] Aspheric surface data

[0449] Page 2

[0450] K=0.00000e+00A4=1.69907e-06A6=2.45484e-10A8=9.28970e-14

[0451] Page 3

[0452] K=0.00000e+00A2=4.34450e-03A4=2.18108e-06A6=-7.80950e-10A8=-7.12257e-15A10=7.10332e-17 Page 4

[0453] K=0.00000e+00A4=-4.67132e-07A6=-7.88299e-10A8=-1.27088e-13

[0454] Page 5

[0455] K=0.00000e+00A4=-3.13196e-07A6=5.03601e-10Page 6

[0456] K=0.00000e+00A4=-5.55144e-07A6=5.69192e-10Page 8

[0457] K=0.00000e+00A4=8.19095e-08A6=-1.48267e-10A8=1.14673e-14

[0458] Page 9

[0459] K=0.00000e+00A4=-5.55144e-07A6=5.69192e-10Page 10

[0460] K=0.00000e+00A4=-3.13196e-07A6=5.03601e-10Page 11

[0461] K=0.00000e+00A4=-4.67132e-07A6=-7.88299e-10A8=-1.27088e-13

[0462] Page 12

[0463] K=0.00000e+00A4=-3.13196e-07A6=5.03601e-10Page 13

[0464] K=0.00000e+00A4=-5.55144e-07A6=5.69192e-10Page 14

[0465] K=0.00000e+00A4=8.19095e-08A6=-1.48267e-10A8=1.14673e-14

[0466] Page 15

[0467] K=0.00000e+00A2=1.79319e-02A4=1.06521e-05A6=2.74699e-09A8=1.71134e-11

[0468] Various data

[0469]

[0470]

[0471] Single lens data

[0472] Numerical example 10 Unit: mm surface data

[0473] Aspheric surface data

[0474] Page 1

[0475] K=0.00000e+00A4=-3.13162e-05A6=2.05836e-07A8=2.98848e-12

[0476] Page 2

[0477] K=0.00000e+00A4=-3.45367e-05A6=2.43905e-07Page 4

[0478] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07Page 5

[0479] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08Page 6

[0480] K=0.00000e+00A4=-2.25614e-06A6=1.02617e-08A8=-1.71753e-11

[0481] Page 7

[0482] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08Page 8

[0483] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07Page 9

[0484] K=0.00000e+00A4=-3.45367e-05A6=2.43905e-07Page 10

[0485] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07 Page 11

[0486] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08 Page 12

[0487] K=0.00000e+00A4=-2.25614e-06A6=1.02617e-08A8=-1.71753e-11

[0488] Page 13

[0489] K=0.00000e+00A2=9.42718e-02A4=7.17789e-04A6=1.90716e-05A8=6.74039e-07

[0490] Various data

[0491]

[0492]

[0493] Single lens data

[0494] Numerical Example 11 Unit: mm Surface Data

[0495]

[0496] Aspheric surface data

[0497] Page 1

[0498] K=0.00000e+00A4=-3.13162e-05A6=2.05836e-07A8=2.98848e-12

[0499] Page 2

[0500] K=0.00000e+00A4=-3.45367e-05A6=2.43905e-07Page 4

[0501] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07Page 5

[0502] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08Page 6

[0503] K=0.00000e+00A4=-2.25614e-06A6=1.02617e-08A8=-1.71753e-11

[0504] Page 7

[0505] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08Page 8

[0506] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07Page 9

[0507] K=0.00000e+00A4=-3.45367e-05A6=2.43905e-07Page 10

[0508] K=0.00000e+00A4=-4.30902e-05A6=1.64429e-07 Page 11

[0509] K=0.00000e+00A4=-2.24284e-05A6=3.63609e-08 Page 12

[0510] K=0.00000e+00A4=-2.25614e-06A6=1.02617e-08A8=-1.71753e-11

[0511] Page 13

[0512] K=0.00000e+00A2=9.42718e-02A4=7.17789e-04A6=1.90716e-05A8=6.74039e-07

[0513] Various data

[0514]

[0515]

[0516] Single lens data

[0517] Numerical Example 12 Unit: mm Surface Data

[0518]

[0519] Aspheric surface data

[0520] Page 2

[0521] K=0.00000e+00A4=2.62580e-06A6=-1.15117e-10A8=3.59052e-14

[0522] Page 3

[0523] K=0.00000e+00A2=1.28550e-03A4=3.33294e-06A6=-2.69495e-09

[0524] A8=7.26662e-13A10=3.26603e-17

[0525] Page 4

[0526] K=0.00000e+00A4=5.86678e-08A6=-1.43048e-09A8=5.92180e-13

[0527] Page 6

[0528] K=0.00000e+00A4=1.99021e-06A6=5.49028e-10Page 7

[0529] K=0.00000e+00A4=1.52785e-06A6=8.65881e-10Page 8

[0530] K=0.00000e+00A4=1.19765e-07A6=-1.92249e-10A8=-1.57989e-14

[0531] Page 9

[0532] K=0.00000e+00A4=1.52785e-06A6=8.65881e-10Page 10

[0533] K=0.00000e+00A4=1.99021e-06A6=5.49028e-10Page 11

[0534] K=0.00000e+00A4=5.86678e-08A6=-1.43048e-09A8=5.92180e-13

[0535] Page 12

[0536] K=0.00000e+00A4=1.99021e-06A6=5.49028e-10Page 13

[0537] K=0.00000e+00A4=1.52785e-06A6=8.65881e-10Page 14

[0538] K=0.00000e+00A4=1.19765e-07A6=-1.92249e-10A8=-1.57989e-14

[0539] Page 15

[0540] K=0.00000e+00A2=1.57692e-02A4=8.16452e-06A6=1.74427e-09A8=9.01082e-12

[0541] Various data

[0542]

[0543]

[0544] Single lens data

[0545]

[0546] Table 1 summarizes the various values ​​used in the conditional expressions in the examples.

[0547] Table 1

[0548]

[0549] The imaging optical system according to each example can be used in an imaging device having an image sensor that receives an image formed by the imaging optical system, such as a camera for a smartphone, a distance detection camera, a fixed-lens camera, and a disposable film camera. The imaging optical system according to each example can also be used for an interchangeable lens for an interchangeable-lens camera. The imaging optical system according to each example can be used in a viewfinder in a camera and an XR device for purposes such as line of sight detection, biometric recognition, and facial expression recognition. In addition, the imaging optical system according to each example can be used in external recognition applications such as XR devices and autonomous robots.

[0550] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

Claims

1. An optical system comprising, in order from the object side to the image side: a first transflective surface, a quarter wave plate, and a second transflective surface, Characterized in that the optical system is a primary imaging system, wherein light from the object side sequentially transmits through the first transflective surface and the quarter-wave plate, is reflected toward the object side by the second transflective surface, transmits through the quarter-wave plate, is reflected toward the image side by the first transflective surface, sequentially transmits through the quarter-wave plate and the second transflective surface, and proceeds toward the image side, and Wherein, the optical system satisfies the following conditional expression: 0.10≤zm1 / f≤0.68 Wherein, zm1 is the distance from the first transflective surface to the image plane on the optical axis, and f is the focal length of the optical system.

2. The optical system according to claim 1, wherein: Satisfy the conditional expression: 0.0≤La×h×Fno / f2≤2.6 Wherein, La is the distance on the optical axis from the lens surface closest to the object to the image plane, h is the radius of the image circle, and Fno is the F number.

3. The optical system according to claim 1 or 2, characterized in that Satisfy the conditional expression: 0.0≤La×h / f2≤2.0 Wherein, La is the distance on the optical axis from the lens surface closest to the object to the image plane, and h is the radius of the image circle.

4. The optical system according to any one of claims 1 to 3, characterized in that Satisfy the conditional expression: 0.50≤Φm1 / Φm2≤1.25 Wherein, Φm1 is the diameter of the first transflective surface, and Φm2 is the diameter of the second transflective surface.

5. The optical system according to any one of claims 1 to 4, characterized in that Satisfy the conditional expression: 0.1≤h / (Φm2 / 2) / Fno≤1.2 Wherein, h is the radius of the image circle, Fno is the F number, and Φm2 is the diameter of the second transflective surface.

6. The optical system according to any one of claims 1 to 5, characterized in that Satisfy the conditional expression: 0.0≤zm2 / La≤0.5 Here, La is the distance from the lens surface closest to the object to the image plane on the optical axis, and zm2 is the distance from the second transflective surface to the image plane on the optical axis.

7. The optical system according to any one of claims 1 to 6, characterized in that Satisfy the conditional expression: 0.0≤Φm1L×f≤1.0 Here, Φm1L is the absolute value of the refractive power of the lens including the second transflective surface.

8. The optical system according to any one of claims 1 to 7, characterized in that Satisfy the conditional expression: 0.0≤AΦr / AΦm≤0.5 Here, AΦr is an average value of absolute values ​​of refractive powers of lenses included in the optical system, and AΦm is an average value of absolute values ​​of refractive powers of the first transflective surface and the second transflective surface.

9. The optical system according to any one of claims 1 to 8, characterized in that One of the first transflective surface and the second transflective surface separates incident light into reflected light and transmitted light according to a polarization state.

10. The optical system according to claim 9, wherein: The other of the first transflective surface and the second transflective surface is a half mirror.

11. The optical system according to any one of claims 1 to 10, characterized in that The shape of an effective area of ​​each of the plurality of lens surfaces included in the optical system is rotationally symmetric with respect to the optical axis.

12. The optical system according to any one of claims 1 to 11, further comprising an aperture stop.

13. The optical system according to claim 12, wherein: The condition expression is satisfied: 0.1≤zp / f≤1.2 Here, zp is the distance from the aperture stop to the image plane on the optical axis.

14. The optical system according to any one of claims 1 to 13, characterized in that The condition expression is satisfied: 0.5≤Fno≤8.0 Wherein, Fno is the F number.

15. The optical system according to any one of claims 1 to 14, characterized in that At least one of the first transflective surface and the second transflective surface is a plane.

16. The optical system according to any one of claims 1 to 15, characterized in that In the wavelength band used, the conditional expression is satisfied: -0.25≤a22≤0.25 -0.25≤a32≤0.25 Wherein, a22 is a 2×2 element of the Mueller matrix corresponding to the quarter-wave plate, and a32 is a 3×2 element of the Mueller matrix.

17. The optical system according to any one of claims 1 to 16, characterized in that The condition expression is satisfied: 0.10≤zm1 / f≤0.

55.

18. A camera device comprising: The optical system according to any one of claims 1 to 17; and an image sensor configured to receive the image formed by the optical system.

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