Optical system, display device, and image capturing device

Abstract

To provide an optical system which offers high optical performance and high reliability.SOLUTION: An optical system (10a) for guiding an image being displayed on a display element (1) to an eyeball of an observer is provided. The optical system comprises: a resin lens (P); and UV light reduction means (S) disposed on the observer side of the resin lens and reducing transmittance for UV light, in which the conditional expressions: 0<Tuv<10, 0<Rir<10 are satisfied where Tuv [%] represents an average transmittance of the UV light reduction means for a wavelength of 300-360 nm and Rir [%] represents an average transmittance for a wavelength of 700-1000 nm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical system, a display device, and an imaging device. [Background technology]

[0002] Conventionally, there is known a gaze detection optical system that detects the direction of the observer's gaze. The gaze detection optical system detects the gaze by irradiating an infrared light source that is not visible to the observer and capturing the reflected image so as not to cause discomfort to the observer. Therefore, in order to achieve good gaze detection performance, it is necessary to reduce reflected light in the infrared wavelength band.

[0003] In addition, it has been widely known that high dispersion resin lenses are used in optical systems for observing display elements such as liquid crystal panels to achieve high optical performance. However, high dispersion resin lenses are inferior to glass lenses in terms of light resistance to ultraviolet light, and therefore require protection by ultraviolet light reduction means to achieve high reliability. Patent Document 1 and Patent Document 2 disclose optical systems in which the light resistance of resin lenses is improved by using ultraviolet light reduction means. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-215389 A [Patent Document 2] JP 2017-26962 A Summary of the Invention [Problem to be solved by the invention]

[0005] The ultraviolet light reduction means disclosed in Patent Document 1 and Patent Document 2 are intended for use only in the ultraviolet and visible light regions, and either have a high reflectance in the infrared region or are not intended for use in the infrared region. In a viewfinder optical system with a gaze detection function using infrared rays, increasing the reflectance in the infrared region is not preferable because it reduces the detection accuracy. In addition, generally, if a steep cutoff wavelength is set in the ultraviolet region, the reflectance in the infrared region tends to increase, so it is necessary to appropriately configure the viewfinder optical system with a gaze detection function.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an optical system having high optical performance and high reliability. [Means for solving the problem]

[0007] An optical system according to one aspect of the present invention is an optical system that guides an image displayed on a display element to an eyeball of an observer, the optical system comprising a resin lens and an ultraviolet ray reduction means that is disposed closer to the observer than the resin lens and reduces transmittance of ultraviolet ray, wherein the average transmittance of the ultraviolet ray reduction means for wavelengths of 300 to 360 nm is Tuv [%] and the average transmittance of the ultraviolet ray reduction means for wavelengths of 700 to 1000 nm is Rir [%], 0 <Tuv<10 0 <Rir<10 The following condition is satisfied.

[0008] Other objects and features of the present invention are illustrated in the following examples. Effect of the Invention

[0009] According to the present invention, it is possible to provide an optical system having high optical performance and high reliability. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of an optical system in the first embodiment. [Diagram 2] 3A to 3C are aberration diagrams of the optical system in Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of an optical system in Example 2. [Figure 4] 11A to 11C are aberration diagrams of the optical system in Example 2. [Diagram 5] FIG. 11 is a cross-sectional view of an optical system according to a third embodiment. [Figure 6] 11A to 11C are aberration diagrams of the optical system in Example 3. [Figure 7] FIG. 11 is a transmittance characteristic diagram of an ultraviolet ray reduction means in Example 4. [Figure 8] FIG. 11 is a reflectance characteristic diagram of an ultraviolet ray reducing means in the fourth embodiment. [Figure 9] FIG. 2 is a schematic diagram of an imaging device including an optical system in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] The optical system (finder optical system) in each embodiment has a plurality of lenses arranged in order from the object side (display surface side) to the observation side (pupil surface side), and has a resin lens P and an ultraviolet ray reduction means S. Note that the resin lens P is a lens made of a resin material, and is not limited to a lens made only of resin, and may contain other materials as long as the lens contains resin as the main material.

[0013] FIG. 1 is a cross-sectional view of an optical system 10a of Example 1 (Numerical Example 1) at a diopter of −1.0 (standard diopter). FIG. 2 is an aberration diagram of the optical system 10a in a reference state. FIG. 3 is a cross-sectional view of an optical system 10b of Example 2 at a diopter of −1.0 (standard diopter). FIG. 4 is an aberration diagram of the optical system 10b at the standard diopter. FIG. 5 is a cross-sectional view of an optical system 10c of Example 3 at a diopter of −1.0 (standard diopter). FIG. 6 is an aberration diagram of the optical system 10c at the standard diopter.

[0014] In each cross-sectional view, 1 is an image display element (display element), 2 is a first lens of each optical system, 3 is a second lens of each optical system, 4 is a third lens of each optical system, 5 is a fourth lens of each optical system, and 6 is a fifth lens of each optical system. In each cross-sectional view, P is a resin lens, S is an ultraviolet light reduction means, and EP is an eye point position (pupil surface) on the observation side. Although not shown in each cross-sectional view, each optical system is equipped with an imaging unit (see FIG. 9) that uses infrared rays to capture an image of the observer's eyeball, and has a gaze detection function that detects the direction of the observer's gaze and uses it for autofocus or automatic exposure setting.

[0015] In each aberration diagram, the spherical aberration diagram shows spherical aberration for the d-line (wavelength 587.56 nm). In the astigmatism diagram, S shows the field curvature for the d-line on the sagittal image plane, and M shows the field curvature for the d-line on the meridional image plane. Distortion aberration is shown for the d-line. The chromatic aberration diagram shows chromatic aberration for the F-line (wavelength 486.13 nm).

[0016] In order to improve visibility, have a sufficiently wide field of view (high magnification), a long eye relief, and to satisfactorily correct various aberrations, it is necessary to appropriately arrange multiple lenses, including a resin lens P. In addition, since the resin lens P deteriorates due to ultraviolet rays and its transmittance and the like change, it is necessary to improve reliability by using an ultraviolet ray reduction means S. On the other hand, to achieve good gaze detection performance, it is necessary to suppress reflected infrared light.

[0017] Therefore, the optical system of each embodiment is an optical system (finder optical system) that guides an image displayed on the image display element 1 to the viewer's eyeball, and has a resin lens P and an ultraviolet ray reduction means S that is arranged on the viewer side of the resin lens P and reduces the transmittance of ultraviolet rays. Furthermore, in each embodiment, when the average transmittance of the ultraviolet ray reduction means S for wavelengths of 300 to 360 nm is Tuv [%] and the average transmittance of the ultraviolet ray reduction means S for wavelengths of 700 to 1000 nm is Rir [%], the following conditional expressions (1) and (2) are satisfied.

[0018] 0 <Tuv<10 ···(1) 0 <Rir<10 ···(2) As a result, the optical system of each embodiment has a good gaze detection function and achieves high optical performance and high reliability. Conditional formula (1) is a conditional formula for improving the environmental resistance of the resin lens P. If the conditional formula (1) is out of the range, the transmittance of the resin lens P will vary, etc., and the visibility of the viewfinder optical system will decrease, which is not preferable. Conditional formula (2) is a conditional formula for achieving a good gaze detection function. If the conditional formula (2) is out of the range, ghost light will be generated in the infrared region, which will reduce the accuracy of the gaze detection function, which is not preferable.

[0019] Preferably, at least one of the numerical ranges of conditional expressions (1) and (2) is set as shown in the following conditional expressions (1a) and (2a), respectively.

[0020] 0 <Tuv<9 ···(1a) 0 <Rir<9 ···(2a) More preferably, at least one of the numerical ranges of the conditional expressions (1) and (2) is set to satisfy the following conditional expressions (1b) and (2b), respectively.

[0021] 0 <Tuv<8 ···(1b) 0 <Rir<8 ···(2b) In each embodiment, it is preferable to satisfy at least one of the following conditional expressions (3) to (7).

[0022] 0 <Tvl<10 ···(3) -1.00 <h*EP / (Re*f)<0.50 ···(4) 0.5 <fuv / f<10.0 ···(5) 1.60 <ndp<1.75 ···(6) 15.0<νdp<25.0 (7) Here, the average reflectance of the ultraviolet ray reduction means S for wavelengths of 400 to 700 nm is Tvl [%]. The curvature of the surface on which the ultraviolet ray reduction means S is provided is Re, the focal length of the entire optical system is f, the diagonal length of the display surface of the image display element 1 is h, the eye point distance of the optical system is EP, and the focal length of the optical member on which the ultraviolet ray reduction means S is provided is fuv. The refractive index of the resin lens P at the d line is ndp, and the Abbe number of the resin lens P at the d line is νdp.

[0023] The technical meanings of conditional expressions (3) to (7) are explained below. Conditional expression (3) is a conditional expression for ensuring good visibility of the optical system. If the upper limit value of conditional expression (3) is exceeded, ghosts in the field of view will increase, and the visibility of the optical system will decrease, which is not preferable.

[0024] Conditional formula (4) is a conditional formula for achieving both good optical performance of the optical system and the characteristics of the ultraviolet ray reduction means S. If the upper limit of conditional formula (4) is exceeded, the curvature of the surface on which the ultraviolet ray reduction means S is provided becomes stronger in the concave direction, which is undesirable as it shortens the effective eyepoint distance. On the other hand, if the lower limit of conditional formula (4) is exceeded, the curvature of the surface on which the ultraviolet ray reduction means S is provided becomes stronger in the convex direction, which increases the exit angle of the light beam from the lens surface, which is undesirable as it becomes difficult to maintain the characteristics of the ultraviolet ray reduction means S.

[0025] Conditional formula (5) is a conditional formula that specifies the ratio of the focal length of the lens provided with the ultraviolet ray reduction means S to the focal length of the entire optical system. Exceeding the upper limit of conditional formula (5) is undesirable because the power of the lens provided with the ultraviolet ray reduction means S becomes weak, resulting in unnecessary design of the optical system. On the other hand, exceeding the lower limit of conditional formula (5) is undesirable because the power of the lens provided with the ultraviolet ray reduction means S becomes strong, which increases the lens curvature and increases the light exit angle with respect to the curved surface, making it difficult to maintain the characteristics of the ultraviolet ray reduction means.

[0026] Conditional formula (6) is a conditional formula that specifies the refractive index at the d-line of the resin lens P. If the upper limit of conditional formula (6) is exceeded, it becomes difficult to correct the Petzval sum of the optical system, and optical performance such as curvature of field or astigmatism deteriorates, which is undesirable. On the other hand, if the lower limit of conditional formula (6) is exceeded, the lens curvature becomes too sharp, which increases spherical aberration, which is undesirable.

[0027] Conditional formula (7) defines the Abbe number at the d-line of the resin lens P. Exceeding the upper limit of conditional formula (7) is undesirable because it becomes difficult to correct chromatic aberration in the optical system due to weak dispersion in the resin lens P. On the other hand, exceeding the lower limit of conditional formula (7) is undesirable because chromatic aberration is overcorrected.

[0028] More preferably, at least one of the numerical ranges of the conditional expressions (3) to (7) is set as in the following conditional expressions (3a) to (7a), respectively.

[0029] 0 <Tvl<8 ···(3a) -1.00 <h*EP / (Re*f)<0.30 ···(4a) 0.5 <fuv / f<8.0 ···(5a) 1.60 <ndp<1.70 ···(6a) 17.0<νdp<25.0 (7a) More preferably, at least one of the numerical ranges of conditional expressions (3) to (7) is set as in the following conditional expressions (3b) to (7b), respectively.

[0030] 0 <Tvl<3 ···(3b) -0.70 <h*EP / (Re*f)<0.10 ···(4b) 0.5 <fuv / f<5.0 ···(5b) 1.62 <ndp<1.70 ···(6b) 19.0<νdp<25.0 (7b) Furthermore, it is preferable that the imaging unit for line of sight detection has an optical axis (optical path) at a different angle from the optical system (finder optical system), and that the imaging unit and the finder optical system do not share lenses in each optical path (see FIG. 9). This is to avoid design waste and reduced optical performance due to unnecessary space being generated in the optical path of the finder optical system when the finder optical system and the imaging unit share an optical axis and optical path. In particular, the higher the magnification of the finder optical system, the shorter the focal length of the entire system becomes, and so it is necessary to shorten the overall length of the optical system.

[0031] The ultraviolet ray reduction means S is a deposition film containing a dielectric or a metal oxide, and the total number of layers of the deposition film is preferably 17 or less. The ultraviolet ray reduction means S may be a deposition film or a material absorption film. When the material absorption is used, the degree of freedom of characteristics is almost eliminated, but the use of the deposition film makes it easier to obtain the desired characteristics. The greater the total number of layers of the deposition film, the easier it is to obtain the desired characteristics in terms of design. On the other hand, since the increase in the number of layers makes the film more susceptible to cracks and makes it difficult to suppress the sensitivity in manufacturing, it is preferable to form the film with the minimum total number required. In addition, the ultraviolet ray reduction means S by the deposition film may be realized by an ultraviolet ray reflecting film or an ultraviolet ray absorbing film.

[0032] Next, Tables 1A, 1B, 2A, 2B, 3A, and 3B show Numerical Examples 1 to 3 corresponding to Examples 1 to 3. Tables 1A and 1B show Numerical Example 1, Tables 2A and 2B show Numerical Example 2, and Tables 3A and 3B show Numerical Example 3. In each Numerical Example, r is the radius of curvature, d is the surface spacing, nd and νd are the refractive index and Abbe number for the d-line, respectively. In addition, when the order from the object side to the observation side is i, di is the surface spacing of the i-th surface. In each Numerical Example, the surfaces with values ​​written in the aspherical data column have an aspherical shape defined by the following formula.

[0033]

number

[0034] In the above formula, x is the distance from the vertex of the lens surface in the optical axis direction, h is the height in the direction perpendicular to the optical axis, r is the paraxial radius of curvature at the vertex of the lens surface, K is the conic constant, and A2, A4, A6, A8, A10, and A12 are polynomial coefficients.

[0035] Table 4 shows the values ​​of conditional expressions (4) and (5) in Numerical Examples 1 to 3.

[0036] Next, a fourth embodiment of the present invention will be described with reference to Figs. 7 and 8. In this embodiment, the ultraviolet ray reduction means S is realized by a multilayer film. Fig. 7 is a transmittance characteristic diagram of the ultraviolet ray reduction means S in this embodiment. In Fig. 7, the horizontal axis indicates wavelength [nm], and the vertical axis indicates transmittance [%]. Fig. 8 is a reflectance characteristic diagram of the ultraviolet ray reduction means S in this embodiment. In Fig. 8, the horizontal axis indicates wavelength [nm], and the vertical axis indicates reflectance [%]. Table 5 shows a numerical embodiment 4 corresponding to this embodiment.

[0037] Next, an imaging device 100 equipped with the optical system (finder optical system) of each embodiment will be described with reference to Fig. 9. Fig. 9 is a schematic diagram of the imaging device 100 equipped with the optical system of each embodiment. The imaging device 100 has an imaging optical system 101, an imaging element 102, an image processing circuit 103, a recording medium 104, and an observation device (display device) 105.

[0038] An object image formed by the imaging optical system 101 is converted into an electrical signal by the imaging element 102. The imaging element 102 is a photoelectric conversion element such as a CCD sensor or a CMOS sensor. The image processing circuit 103 processes the electrical signal output from the imaging element 102 to generate an image (image data). The recording medium 104 is a semiconductor memory, a magnetic tape, an optical disk, or the like, and records the image generated by the image processing circuit 103. The image generated by the image processing circuit 103 is displayed on an observation device 105 equipped with the optical system of each embodiment.

[0039] The observation device 105 includes an image display element 1051 and a finder optical system 1052 (corresponding to the optical system in each embodiment), an illumination system 1053 for illuminating the observer's eyeball 106, and an imaging unit 1054 for imaging the observer's eyeball. The image display element 1051 is a liquid crystal display element or an organic EL, etc. The illumination system 1053 is disposed to illuminate the observer's eyeball and is an LED, etc. It is preferable to use near-infrared light as the illumination wavelength of the illumination system 1053 so that the observer does not feel uncomfortable. The imaging sensor 1055 is a CCD sensor or a CMOS sensor. The imaging optical system 101 for imaging the observer's eyeball 106 can be disposed at any position outside the optical path of the finder optical system 1052. It is preferable to dispose it below the imaging device 100 while avoiding interference with other components, since this can prevent the height of the imaging device 100 from increasing.

[0040] As shown in FIG. 9, preferably, the optical axis OA2 of the imaging unit 1054 and the optical axis OA1 of the viewfinder optical system 1052 are at different angles to each other, and the imaging unit 1054 and the viewfinder optical system 1052 do not share a lens with each other.

[0041] In this way, in each embodiment, the observation device 105 equipped with the viewfinder optical system 1052 can be applied to the imaging device 100 such as a digital camera or video camera. This makes it possible to provide an optical system that has a line of sight detection function, a wide viewing angle as a viewfinder, a long eye point, and high optical performance. Therefore, according to each embodiment, it is possible to provide an optical system, a display device, and an imaging device that have high optical performance and high reliability.

[0042] [Table 1A]

[0043] [Table 1B]

[0044] [Table 2A]

[0045] [Table 2B]

[0046] [Table 3A]

[0047] [Table 3B]

[0048] [Table 4]

[0049] [Table 5]

[0050] The disclosure of each embodiment includes the following configuration.

[0051] (Configuration 1) An optical system that guides an image displayed on a display element to an observer's eyeball, A plastic lens, an ultraviolet ray reducing means arranged on the viewer side of the resin lens and configured to reduce transmittance of ultraviolet rays; When the average transmittance of the ultraviolet ray reduction means at wavelengths of 300 to 360 nm is Tuv [%] and the average transmittance of the ultraviolet ray reduction means at wavelengths of 700 to 1000 nm is Rir [%], 0 <Tuv<10 0 <Rir<10 An optical system characterized in that the following condition is satisfied: (Configuration 2) When the average reflectance of the ultraviolet ray reducing means at wavelengths of 400 to 700 nm is Tvl [%], 0 <Tvl<10 2. The optical system according to claim 1, wherein the following condition is satisfied: (Configuration 3) the ultraviolet ray reducing means is provided on an optical surface of the optical system closest to a viewer, Let Re be the curvature of the optical surface, f be the focal length of the optical system, h be the diagonal length of the display surface of the display element, and EP be the eye point distance of the optical system. -1.00 <h*EP / (Re*f)<0.50 3. The optical system according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 4) When the focal length of the optical member in which the ultraviolet ray reduction means is provided is fuv and the focal length of the optical system is f, 0.5 <fuv / f<10.0 4. The optical system according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) 5. The optical system according to any one of configurations 1 to 4, further comprising an imaging unit that images the eyeball using infrared rays. (Configuration 6) an optical axis of the imaging unit and an optical axis of the optical system are at different angles to each other; The optical system according to configuration 5, wherein the imaging unit and the optical system do not share a lens with each other. (Configuration 7) the ultraviolet ray reducing means is a vapor deposition film containing a dielectric or a metal oxide, 7. The optical system according to any one of configurations 1 to 6, wherein the total number of layers of the evaporated films is 17 or less. (Configuration 8) When the refractive index of the resin lens at the d line is ndp and the Abbe number at the d line is νdp, 1.60 <ndp<1.75 15.0<νdp<25.0 8. The optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) A display device comprising the optical system according to any one of configurations 1 to 8 and a display element. (Configuration 10) An imaging device comprising the display device according to configuration 9 and an imaging element.

[0052] 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 are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0053] 1. Image display element (display element) 10a, 10b, 10c optics P resin lens S UV reduction measures

Claims

1. An optical system that guides an image displayed on a display element to an observer's eyeball, A plastic lens, an ultraviolet light reducing means disposed closer to the viewer than the resin lens and reducing the transmittance of ultraviolet light; When the average transmittance of the ultraviolet ray reducing means for wavelengths of 300 to 360 nm is Tuv [%] and the average reflectance of the ultraviolet ray reducing means for wavelengths of 700 to 1000 nm is Rir [%], 0<Tuv<10 0<Rir<10 An optical system characterized by satisfying the following conditional expression:

2. When the average reflectance of the ultraviolet ray reducing means for wavelengths of 400 to 700 nm is Tvl [%], 0<Tvl<10 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. the ultraviolet light reducing means is provided on an optical surface of the optical system closest to the viewer, When the curvature of the optical surface is Re, the focal length of the optical system is f, the diagonal length of the display surface of the display element is h, and the eye point distance of the optical system is EP, -1.00<h*EP / (Re*f)<0.50 2. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the optical member provided with the ultraviolet light reducing means is fuv and the focal length of the optical system is f, 0.5<fuv / f<10.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

5. 2. The optical system according to claim 1, further comprising an imaging unit that images the eyeball using infrared rays.

6. an optical axis of the imaging unit and an optical axis of the optical system are at different angles from each other; The optical system according to claim 5 , wherein the imaging unit and the optical system do not share a lens with each other.

7. the ultraviolet ray reducing means is a vapor-deposited film containing a dielectric or a metal oxide, 2. The optical system according to claim 1, wherein the total number of layers of the evaporated films is 17 or less.

8. When the refractive index of the resin lens at the d line is ndp and the Abbe number at the d line is νdp, 1.60<ndp<1.75 15.0<νdp<25.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

9. A display device comprising the optical system according to claim 1 and a display element.

10. An imaging device comprising: the display device according to claim 9; and an imaging element.

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