JP4873996B2 - Optical element - Google Patents

Description

  The present invention relates to an optical element in which a plurality of lenses of an optical system including a plurality of lenses and a holding frame for the lenses are integrated.

  Conventionally, in a lens included in an optical system applied to an imaging device, an observation device, etc., a light beam that is refracted by being incident within the maximum incident aperture of a light beam that contributes to image formation and reflected by the outer peripheral surface of the lens is used as a contrast of the image In order to prevent unnecessary light rays that cause flare, which is a cause of lowering of light, a light absorbing material is applied to the outer peripheral surface of the lens to attenuate or extinguish stray light reflected on the outer peripheral surface of the lens. I tried not to reach the image plane.

FIG. 4 is a partial cross-sectional view showing an example of a conventional optical element that includes a lens included in an optical system and a holding frame for the lens.
The optical element shown in the figure includes a lens L ₁₀₁ that is a convex meniscus lens, and a matte black lens holding frame K ₁₀₁ that holds the lens L ₁₀₁ . The outer peripheral surface of the lens L ₁₀₁ has a surface accuracy in a rough state of 1 μm to several μm, and the coating film M is coated on the outer peripheral surface with a black paint of a light absorbing material having a thickness of about 0.1 to 0.2 mm. ₁₀₁ is provided.

This configuration, as indicated by an arrow in the figure, light in the lens L ₁₀₁ refracted reaches the outer circumferential surface of the lens L ₁₀₁ with the law of refraction light is incident on the maximum entrance aperture of the lens L ₁₀₁ However, the outer peripheral surface having the rough surface accuracy and the light absorbing material provided on the outer peripheral surface are absorbed or attenuated without reflecting off the outer peripheral surface, so that the light does not enter the optical path to be imaged. It has become.

In addition to the method shown in the figure, as a method for preventing unnecessary rays from reaching the imaging surface, for example, in Patent Document 1, the convex surface of the lens reaches the lens outer shape from the inner side in the radial direction from the edge portion. A photographic lens has been proposed in which the light is shielded by a masking means.
JP-A-2005-77616

  However, in the case of the optical element configured as shown in FIG. 4 in order to prevent the harmful light rays that do not contribute to the image formation to reach the image formation surface, the light applied to the outer peripheral surface of the lens The coating material, which is an absorbent material, requires a film thickness that exceeds the dimensional accuracy to ensure optical performance in order to shield the inside of the optical system, the film thickness is non-uniform, and the lens holding frame and other optical elements. Since the lens is inclined or biased at the fitting part or the contact part, it is not easy to ensure the required dimensional accuracy.

  In view of the above circumstances, the present invention reduces harmful and unnecessary stray light that does not contribute to image formation in an optical element including a lens and a lens holding frame without providing a light shielding unit or a light absorbing unit. An object of the present invention is to provide an optical element that can be used.

In order to achieve the above object, an optical element according to a first aspect of the present invention is an optical element in which a plurality of lenses of an optical system including a plurality of lenses and a holding frame of the lens are integrated. The lens of the optical element has a positive refracting power whose convex surface on the incident surface side is convex, and in the lens of the optical element, the radius of curvature of the curved surface on the incident surface side at the incident position of the light beam is set. R _{1 is} the maximum incidence of light rays that contribute to imaging, where φd ₁ is the aperture whose radius is the distance between the incident position and the optical axis, φd _{2 is} the outer diameter of the lens, and n is the refractive index of the lens. Within the caliber,
arcsin (1 / n) ≦ arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}) (1),
and,
d ₁ <d ₂ (2),
Have a position of incidence of satisfying beam, said light beam incident on the incident position is characterized in that it is not irradiated to the holding frame for holding the lens in the optical element directly.

According to this optical element, on the incident surface side curved surface within the maximum incident aperture of the lens, firstly,
arcsin (1 / n) = arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}) (1a),
And an angle (formula (1a) formed by the ray in the lens that is refracted by being incident on the incident position and the normal of the curved surface at the incident position. ) And the angle formed by the normal of the curved surface at the incident position (the angle represented by the right side of equation (1a)) is the same. That is, the light beam incident on the incident position satisfying the above expressions (1a) and (2) passes through the lens parallel to the optical axis after refraction.

Second, when the light beam is incident on a position outside the incident position that satisfies the above equations (1a) and (2) and within the maximum incident aperture,
arcsin (1 / n) <arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}) (1b),
And the above formula (2), and the angle formed by the ray in the lens incident and refracted at this position and the normal of the curved surface at the incident position (the angle represented by the left side of formula (1a)) Is smaller than the angle formed by the optical axis and the normal of the curved surface at the incident position (the angle represented by the right side of equation (1a)). That is, the light beam that has entered the incident position satisfying the above expressions (1b) and (2) passes through the lens in a direction that converges on the optical axis after refraction.

  As a result, the light beam that has entered the incident position satisfying the above formulas (1) ((1a) or (1b)) and (2) does not go directly to the outer peripheral surface after refraction, but is reflected by the outer peripheral surface. Things will disappear. Therefore, generation of harmful light rays that travel in the imaging optical path and cause flare due to reflection is eliminated, and it is not necessary to provide light shielding means and light absorption means in the optical element.

An optical element according to a second aspect of the present invention is the lens according to the first aspect, in the first aspect, in the formula (1),
arcsin (1 / n) = arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}),
And an aperture whose diameter is the distance between the incident position of the light beam on the incident surface side curved surface and the optical axis, which is inside the aperture φd ₁ when satisfying the expression (2), is φd ₃ , Where R _{2 is} the radius of curvature at the incident position where the distance is the radius of the aperture φd ₃ , and t is the thickness in the optical axis direction at the outer periphery of the lens.
arcsin (1 / n)> arctan ((d 3/2) / √ {R 2 ^ 2- (d 3/2) ^ 2}) (3),
and,
_{arctan [{(d 2 -d 3} ) / 2} / (t + √ {R 2 ^ 2- (d 3/2) ^ 2} -√ {R 2 ^ 2- (d 2/2) ^ 2}) _{] + arcsin {(d 3/} 2) / R 2}> arcsin (1 / n) (4),
It has the incident position of the light beam which satisfies the following.

  According to this optical element, the light ray in the lens refracted by being incident on the incident position satisfying the above equations (1b), (2), (3) and (4), and the normal of the curved surface at the incident position (The angle represented by the left side of the expression (3)) satisfies the above expression (3), so that the angle between the optical axis and the normal of the curved surface at the incident position (the expression (3)) The angle of the light beam in the lens after refraction travels in the lens in a direction away from the optical axis, but satisfies the above equation (4). The light rays in the lens after refraction are emitted from the optical surface having surface accuracy that satisfies the optical performance of the optical system.

  As a result, the light beam that has entered the incident position satisfying the above equations (1b), (2), (3), and (4) does not go directly to the outer peripheral surface after refraction, but is reflected by the outer peripheral surface. Will disappear. Therefore, generation of harmful light rays that travel in the imaging optical path and cause flare due to reflection is eliminated, and it is not necessary to provide light shielding means and light absorption means in the optical element.

  The optical element according to a third aspect of the present invention is incident on the lens of the optical element in the first aspect within the maximum incident aperture when the expressions (1) and (2) are satisfied. The light emission position is within an optical surface having surface accuracy that satisfies the optical performance of the optical system.

  According to this optical element, a light beam incident on an incident position within the maximum incident aperture satisfying the above expressions (1) and (2) does not go directly to the outer peripheral surface after refraction but is reflected by the outer peripheral surface. Things will disappear. Therefore, generation of harmful light rays that travel in the imaging optical path and cause flare due to reflection is eliminated, and it is not necessary to provide light shielding means and light absorption means in the optical element.

  According to the present invention, in an optical element configured by integrating a lens and a lens holding frame, harmful and unnecessary stray light that does not contribute to image formation can be reduced without providing a light shielding unit or a light absorbing unit. Therefore, flare is reduced and image performance can be improved.

Further, since the surface treatment of the lens holding frame and the coating of the optical element are not required, the dimensional accuracy is stabilized and the optical performance can be improved.
Furthermore, since there is no light beam that travels directly from the curved surface on the incident surface side to the lens outer peripheral surface and is reflected, the influence of the color and gloss of the lens holding frame material on the optical system is reduced, and any material or color can be adopted. Thus, the degree of freedom of selection can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial cross-sectional view of an optical element according to Example 1 of the present invention.
The optical element 1 shown in the figure includes a plurality of lenses L _{0 of} an optical system (not shown) composed of a plurality of lenses, and a holding frame (hereinafter referred to as “lens holding frame”) K _{0 of the} lens L _0. Is an integrated optical element.

In the figure, x ₀ x ₀ ′ is the optical axis of the lens L ₀ .
The lens L ₀ is a convex meniscus lens having a convex surface on the incident surface side.
In the lens L ₀ , the aperture φd ₀₁ is smaller than the maximum incident aperture that contributes to the image formation of incident light rays. The incident position Q of the light beam is an incident position on the incident aperture diameter φd ₀₁ on the incident surface side curved surface of the lens L ₀ . The curvature radius R ₀₁ is the curvature radius of the curved surface at the incident position Q. The angle θ ₀ is an angle formed between the normal line of the curved surface (curved surface having the curvature radius R ₀₁ ) at the incident position Q and the optical axis x ₀ x ₀ ′. The aperture φd ₀₂ is the outer diameter of the lens L ₀ (that is, φd ₀₁ <φd ₀₂ ). t ₀ is the thickness in the optical axis direction on the outer periphery of the lens L ₀ . The refractive index of the lens L ₀ is n ₀ .

In this embodiment, the entrance aperture .phi.d ₀₁ = 10 mm, an outer diameter .phi.d ₀₂ = 11 mm, the curvature of the curved surface at the incident position Q radius R ₀₁ = 9.0305mm, the optical axis direction thickness t ₀ of the outer periphery of the lens L ₀ of the lens L ₀ = 1.8 mm, and a refractive index n ₀ = 1.80610 lens L ₀ to.

Lens holding frame K ₀ is the lens L ₀ holds, fitted with the outer peripheral surface of the lens L _0, is constructed integrally with the lens L _0.
In the optical element 1 having such a configuration, the angle θ ₀ formed by the normal line of the curved surface (curved surface having the curvature radius R ₀₁ ) at the incident position Q of the light beam and the optical axis x ₀ x ₀ ′ is expressed by the above equation (1). It can be obtained from the right side of

theta ₀ = right side of equation (1) = arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2})
= Arctan ((10/2) / √ {9.0305 ^ 2- (10/2) ^ 2})
= 33.6198 °
(Where d ₁ = d ₀₁ , R ₁ = R ₀₁ ).

Further, the maximum incident angle i ₀ at which the angle formed between the light ray incident on the incident position Q and entering the direction away from the optical axis and the normal line of the curved surface at the incident position Q is the maximum is the law of refraction. From the critical angle. That is, the maximum incident angle i ₀ = 90 °. Therefore, (the angle between the normal line of the curved surface in the light incident position Q in the lens L ₀ refracted incident on the incident position Q) refraction angle alpha ₀ in the lens L ₀ at an incident position Q in this case is , From the left side of the above equation (1). That is,
sin90 ° / sinα ₀ = n
1 / sinα ₀ = n
α ₀ = arcsin (1 / n) = left side of equation (1)
α ₀ = arcsin (1 / 1.80610) = 33.6198 °
(Where n = n ₀ ). Than this,
α ₀ = θ ₀ = 33.6198 °
It becomes.

That is, since the refraction angle α ₀ and the angle θ ₀ are the same, the light ray that has entered the incident position Q and is refracted travels in the lens L ₀ parallel to the optical axis x ₀ x ₀ ′. Therefore, the exit aperture whose radius is the distance between the exit position of the exit surface side curved surface of the lens L ₀ and the optical axis x ₀ x ₀ ′ is the radius between the incident position Q and the optical axis x ₀ x ₀ ′. It is the same as the entrance aperture and is 10mm.

In the optical element 1 shown in the figure, when the incident position of the light beam is larger than the incident aperture diameter φd _{01 and} on the incident aperture diameter φd ₀₄ = 10.4 mm within the maximum incident aperture diameter, When the left side and the right side of the above equation (1) are obtained,
Left side of equation (1) = arcsin (1 / n)
= Arcsin (1 / 1.80610)
= 33.6198 °
(Where n = n ₀ ). The right side of the above equation (1) is
Right = arctan of formula _{(1) ((d 1/} 2) / √ {R 1 ^ 2- (d 1/2) ^ 2})
= Arctan ((10.4 / 2) / √ {9.0305 ^ 2- (10.4 / 2) ^ 2})
= 35.l58 °
(Where d ₁ = d ₀₄ , R ₁ = R ₀₁ ).

Therefore, the left side is less than the right side, and the angle formed between the ray in the lens L ₀ that is incident and refracted on the incident position on the incident aperture φd ₀₄ and the normal of the curved surface at the incident position is the optical axis x ₀ x ₀ ′ and its angle It becomes smaller than the angle formed by the normal of the curved surface at the incident position. That is, the light beam that has entered the incident position passes through the lens L ₀ in a direction that converges on the optical axis x ₀ x ₀ ′ after refraction.

Further, in the optical element 1 shown in the figure, when the incident position of the light beam is on the incident aperture diameter φd ₀₃ smaller than the incident aperture diameter φd ₀₁ , and in this embodiment, φd ₀₃ = 8 mm, the above formula (3) The left side is
Left side of equation (3) = arcsin (1 / n)
= Arcsin (1 / 1.80610)
= 33.6198 °
(Where n = n ₀ ). The right side of the above equation (3) is
Right side of equation (3) = arctan ((d 3/2) / √ {R 2 ^ 2- (d 1/2) ^ 2})
= Arctan ((8/2) / √ {9.0305 ^ 2- (8/2) ^ 2})
= 26.292 °
(Where d ₃ = d ₀₃ , R ₂ = R ₀₁ , d ₁ = d ₀₁ ).

Therefore, the left side is greater than the right side, and the above formula (3) is satisfied. Therefore, in this case, the light beam incident on the lens L ₀ , that is, the light beam incident on the incident aperture φd ₀₃ travels in the lens L ₀ in a direction away from the optical axis x ₀ x ₀ ′ after refraction. .

In the above formula (4), the left side is
Left = arctan of formula _{(4) [{(d 2} -d 3) / 2} / (t + √ {R 2 ^ 2- (d 3/2) ^ 2} -√ {R 2 ^ 2- (d 2 / 2) ^ 2})] + arcsin {(d 3/2) / R 2}
= Arctan [{(11-8) / 2} / (1.8 + √ {9.0305 ^ 2- (8/2) ^ 2} -√ {9.0305 ^ 2- (11/2) ^ 2})] + arcsin { (8/2) /9.0305}
= 55.044 °
(Where d ₂ = d ₀₂ , d ₃ = d ₀₃ , t = t ₀ , R ₂ = R ₀₁ ). The right side of the above equation (4) is
Right side of equation (4) = arcsin (1 / n)
= Arcsin (1 / 1.80610)
= 33.620 °
(Where n = n ₀ ). Therefore, the left side is greater than the right side, and the above formula (4) is satisfied. Therefore, in this case, the light beam incident on the lens L ₀ , that is, the light beam incident on the incident aperture φd ₀₃ travels in the lens L ₀ in a direction away from the optical axis x ₀ x ₀ ′, and exits from the lens L ₀ . The light is emitted from the surface of the optical surface having a surface accuracy that satisfies the optical performance of the optical system including the lens L ₀ .

As described above, according to the optical element 1 according to this embodiment, light incident on the incident position to satisfy the above equation in the lens L ₀ is not proceed directly to the outer peripheral surface of the lens L _0, reflected by the outer peripheral surface There is no need to do it. Therefore, such a surface treatment or coating or the like for anti-reflection of the lens holding frame K _0, without providing the shielding means and the light absorbing means, harmful and unwanted stray light not contributing to imaging can be reduced. This also reduces flare and improves image performance.

Further, since the surface treatment of the lens holding frame K ₀ and the coating of the optical element 1 are not required, the dimensional accuracy is stabilized and the optical performance can be improved.
Further, since there is no light beam that travels directly from the incident surface side curved surface of the lens L ₀ to the lens outer peripheral surface and is reflected, the influence of the color and gloss of the material of the lens holding frame K _{0 on} the optical system is reduced, and any material can be used. Or a color can be adopted and the freedom degree of selection can be increased.

  FIG. 2A is a cross-sectional view of a photographic lens having an optical system including an optical element according to Example 2 of the present invention, and also shows a part of light rays contributing to image formation. FIG. 2B is a cross-sectional view of the optical element according to the present example. FIG. 3 is a cross-sectional view of a photographic lens having an optical system including an optical element according to the present embodiment, and is a view also showing a part of light rays passing through the optical element.

2A, 2 </ b> B, and 3, x ₁ x ₁ ′ is the optical axis of the photographing lens 2.
In the photographing lens 2 shown in FIGS. 2 (a) and 3, the matte black lens frame K ₁ holds the first lens L ₁ and the second lens L ₂ and does not require the third lens L ₃ . such imaged has a portion S ₃ for blocking the light rays do not contribute, matte-like black ring s ₁ holding the first lens L _1, securing the second lens L ₂ in caulking portion s _2. Further, the lens frame K ₁ holds the optical element 3 shown in FIG. 2B in which the third lens L ₃ and the lens holding frame K ₂ that holds the third lens L ₃ are integrated.

The optical element 3 is fixed to the lens frame K ₁ with a fastening member (not shown) in the vicinity of the imaging side of the part s ₃ that blocks the light beam that does not contribute to unnecessary imaging.
The matte-shaped black lens frame K ₃ that holds the fourth lens L ₄ has an iris diaphragm function, and has a portion s ₄ that blocks unnecessary rays, and is held by the lens frame K ₁ .

The fifth lens L ₅ and the sixth lens L ₆ are cemented lenses, and the matte black lens frame K ₄ that holds the cemented lenses has a portion s ₅ that blocks unwanted light rays. It held in the lens frame K ₁ and.

The matte black lens frame K ₅ that holds the seventh lens L ₇ has a portion s ₆ that blocks unnecessary light and is held by the lens frame K ₁ .
A matte black mirror frame K ₆ that holds the filter L ₈ and the filter L ₉ is fixed together with the lens frame K ₁ to a camera unit that holds an imager (not shown) that is the imaging plane I. Has been.

In this embodiment, the lens data of the taking lens 2 is as follows.
r ₁ = 16.9916 d ₁ = 2.5081 n ₁ = 1.65160 ν ₁ = 58.55
r ₂ = 267.3736 d ₂ = 0.5000
r ₃ = -386.8516 d ₃ = 0.8000 n ₃ = 1.72916 ν ₃ = 54.68
r ₄ = 4.6000 d ₄ = 0.8500
r ₅ = 5.0500 d ₅ = 1.6500 n ₅ = 1.83917 ν ₅ = 23.86
r ₆ = 6.7896 d ₆ = 8.8657
r ₇ = ∞ (aperture) d ₇ = 0.5000
r ₈ = 4.9793 d ₈ = 1.2011 n ₈ = 1.69350 ν ₈ = 53.21
r ₉ = 44.9996 d ₉ = 0.4000
r ₁₀ = 6.8040 d ₁₀ = 1.3489 n ₁₀ = 1.68893 ν ₁₀ = 31.16
r ₁₁ = 60.0000 d ₁₁ = 0.2500 n ₁₁ = 1.70200 ν ₁₁ = 40.20
r ₁₂ = 3.6512 d ₁₂ = 2.3919
r ₁₃ = 11.0558 d ₁₃ = 1.0000 n ₁₃ = 1.79950 ν ₁₃ = 42.34
r ₁₄ = -62.0049 d ₁₄ = 4.2148
r ₁₅ = ∞ d ₁₅ = 0.7600 n ₁₅ = 1.60625 ν ₁₅ = 63.71
r ₁₆ = ∞ d ₁₆ = 0.5000
r ₁₇ = ∞ d ₁₇ = 0.5556 n ₁₇ = 1.51633 ν ₁₇ = 64.14
r ₁₈ = ∞ d ₁₈ = 0.5000
I ₁ (imaging plane)
F number = 4.0, IH (imaging surface height) = 3.6mm, f (focal length) = 7.326mm
However, in the above lens data, r _{1 to} r ₁₈ each indicate a radius of curvature (mm). That is, r ₁ and r ₂ are the curvature radii of the incident side and the exit side of the first lens L ₁ . r ₃ and r ₄ are the radii of curvature of the incident side and the exit side of the second lens L ₂ . r ₅ and r ₆ are the radii of curvature of the entrance side and the exit side of the third lens L ₃ . r ₇ is a radius of curvature of a diaphragm (not shown). r ₈ and r ₉ are the radii of curvature of the entrance side and exit side of the fourth lens L ₄ . r ₁₀ is the radius of curvature of the fifth lens L _{5 on} the incident side. r ₁₁ is the radius of curvature on the exit side of the fifth lens L _{5 and} the radius of curvature on the incident side of the sixth lens L ₆ . r ₁₂ is the radius of curvature on the exit side of the sixth lens L ₆ . r ₁₃ and r ₁₄ are the curvature radii of the seventh lens L _{7 on} the incident side and the emission side. r ₁₅ and r ₁₆ are the radii of curvature of the entrance side and the exit side of the filter L ₈ . r ₁₇ and r ₁₈ are the curvature radii of the incident side and the outgoing side of the filter L ₉ .

D _{1 to} d ₁₈ indicate distances (mm) on the optical axis of the photographing lens 2, respectively. That is, d ₁ is the thickness of the first lens L ₁ . d ₂ is the distance of the space between the first lens L ₁ and the second lens L ₂ . d ₃ is the thickness of the second lens L ₂ . d ₄ is the distance of the space between the second lens L ₂ and the third lens L ₃ . d ₅ is the thickness of the third lens L ₃ . d ₆ is the distance of the space between the third lens L ₃ and a diaphragm (not shown). d ₇ is the distance of the space between the diaphragm (not shown) and the fourth lens L ₄ . d ₈ is the thickness of the fourth lens L ₄ . d ₉ is the distance of the space between the fourth lens L ₄ and the fifth lens L ₅ . d ₁₀ is the thickness of the fifth lens L ₅ . d ₁₁ is the thickness of the sixth lens L ₆ . d ₁₂ is the distance of the space between the sixth lens L ₆ and the seventh lens L ₇ . d ₁₃ is the thickness of the seventh lens L ₇ . d ₁₄ is the distance of the space between the seventh lens L ₇ and filter L _8. d ₁₅ is the thickness of the filter L ₈ . d ₁₆ is the distance of the space between the filters L ₈ and L ₉ . d ₁₇ is the thickness of the filter L ₉ . d ₁₈ is the distance of the space between the filter L ₉ and the imaging plane I ₁ .

N ₁ and ν ₁ are the refractive index and dispersion of the first lens L ₁ . n ₃ and ν ₃ are the refractive index and dispersion of the second lens L ₂ . n ₅ and ν ₅ are the refractive index and dispersion of the third lens L ₃ . n ₈ and ν ₈ are the refractive index and dispersion of the fourth lens L ₄ . n ₁₀ and ν ₁₀ are the refractive index and dispersion of the fifth lens L ₅ . n ₁₁ and ν ₁₁ are the refractive index and dispersion of the sixth lens L ₆ . n ₁₃ and ν ₁₃ are the refractive index and dispersion of the seventh lens L ₇ . n ₁₅ and ν ₁₅ are the refractive index and dispersion of the filter L ₈ . n ₁₇ and ν ₁₇ are the refractive index and dispersion of the filter L ₉ .

In the photographic lens 2 configured as described above, the optical element 3 formed by integrating the third lens L ₃ and the lens holding frame K ₂ is the third lens as shown in FIG. A light ray in the lens L ₃ refracted by entering L ₃ has an incident position of the light ray parallel to the optical axis x ₁ x ₁ ′, and enters the third lens L ₃ as shown in FIG. The incident position of the light beam traveling in the direction in which the light beam in the lens L ₃ refracted converges on the optical axis x ₁ x ₁ ′, and the incident position of the light beam traveling in the direction away from the optical axis x ₁ x ₁ ′ Have

First, as shown in FIG. 2B, the case where the light beam in the lens L ₃ refracted by being incident on the third lens L ₃ is parallel to the optical axis x ₁ x ₁ ′ will be described.
As shown in FIG. 2A, the light beam incident on the third lens L ₃ is regulated by a portion s ₃ that blocks an unnecessary light beam that does not contribute to the imaging of the lens frame K ₁ . That is, the inner diameter of the part s ₃ matches the maximum diameter of the light beam that can enter the third lens L ₃ .

In this embodiment, the inner diameter φd ₂₁₁ of the part s ₃ is set to 7.876 mm, which is the maximum incident aperture of the third lens L ₃ . Further, from the lens data, in the third lens L ₃ , the refractive index n ₅ = 1.83917 and the curvature radius r ₅ = 5.0500 of the incident surface. In the third lens L ₃ , the thickness t ₁ in the optical axis x ₁ x ₁ ′ direction on the outer periphery is set to 0.661 mm, and the outer diameter φd ₂₁₂ is set to 8.9 mm.

Of the light rays incident on the incident surface side curved surface of the third lens L ₃ , the incident angle of the light ray that can be emitted to the outermost side (the direction away from the optical axis x ₁ x ₁ ′) is 90 °, which is a critical angle for total reflection. It becomes. In this case, if the refraction angle with respect to the normal of the light beam after refraction at the incident position (the normal of the curved surface at the incident position) is α ₁ , α ₁ can be obtained from the left side of the above equation (1).

α ₁ = arcsin (sin90 ° / n)
= Arcsin (1 / n) = left side of equation (1) = arcsin (1 / 1.83917)
= 32.937 °
(However, n = n ₅ )
When the refraction angle α ₁ is equal to the angle θ ₁₀ formed by the normal line and the optical axis x ₁ x ₁ ′, the aperture (incidence) has a radius between the incident position of the light beam and the optical axis x ₁ x ₁ ′. When the aperture is φd ₂₁₃ , the right side of the above formula (1) is
Right = arctan of formula _{(1) ((d 1/} 2) / √ {R 1 ^ 2- (d 1/2) ^ 2})
Because
_{θ 10 = arctan ((d 213} /2) / √ {r 5 ^ 2- (d 213/2) ^ 2})
(Where d ₁ = d ₂₁₃ , R ₁ = r ₅ ). Here, when d ₂₁₃ is solved,
_{d 213 = √ {4 · r} 5 ^ 2 · (tanθ 10) ^ 2} / (1 + tanθ 10)
= √ {4 ・ 5.050 ^ 2 ・ (tan32.937) ^ 2} / (1 + tan32.937)
= 5.492
Accordingly, a light beam incident at an incident angle of 90 ° on an incident aperture diameter φd ₂₁₃ = 5.492 mm within the maximum incident aperture diameter φd ₂₁₁ = 7.876 mm is, after refraction, the third lens L ₃ as shown in FIG. The light travels in parallel with the optical axis x ₁ x ₁ ′.

In addition, a light beam that is outside the incident aperture diameter φd ₂₁₃ = 5.492 mm and entered within the maximum incident aperture diameter φd ₂₁₁ = 7.876 mm is, after refraction, the third lens L ₃ after being refracted like one of the light beams indicated by the arrows in FIG. It travels in a direction that converges on the optical axis x ₁ x ₁ ′. Next, this case will be described.

As an example, here, a light ray incident on a position on the maximum incident aperture is considered. When the angle between the normal and the optical axis x ₁ x ₁ 'of the curved surface at the position of the maximum entrance aperture and theta _11, theta ₁₁ can be obtained by the right side of the above equation (1).

theta ₁₁ = right side of equation (1) = arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2})
θ ₁₁ = arctan ((7.876 / 2) / √ {5.05 ^ 2- (7.876 / 2) ^ 2})
θ ₁₁ = 51.242 °
(Where d ₁ = d ₂₁₁ , R ₁ = r ₅ ).

Moreover, the left side of said Formula (1) is 32.937 degrees as calculated | required above.
Therefore, the light ray incident on the position where the left side is less than the right side and which is on the maximum entrance aperture is refracted in the third lens L ₃ after being refracted, like one of the light rays indicated by the arrows in FIG. ₃ , and the optical axis x ₁ x ₁ ′. Proceed to converge.

As described above, the angle (θ ₁₀ ) formed by the normal line of the curved surface at the incident position of the third lens L ₃ and the optical axis x ₁ x ₁ ′, and the third lens L ₃ refracted by being incident on the incident position. The angle (α ₁ ) between the light beam and its normal line is the same, and the light beam in the third lens L ₃ and the optical axis x ₁ x ₁ ′ are parallel to each other in the above formula (1) and The presence of an incident position satisfying (2) is outside the aperture (φd ₂₁₃ ) whose radius is the distance between the incident position and the optical axis x ₁ x ₁ ′ and the maximum incident aperture (φd ₂₁₁ ). Since the light beam incident on the inner position travels in the third lens L ₃ in a direction converged on the optical axis x ₁ x ₁ ′ after refraction, there is no direct light beam toward the outer peripheral surface of the third lens L _3. Become. Further, from the above equation (2), there is a certain distance between the outer peripheral surface of the third lens L3 and the incident position of the light beam, and the generation of the light beam reflected by the outer peripheral surface is eliminated.

In addition, a light beam that is within the maximum incident aperture diameter φd ₂₁₁ = 7.876 mm and is incident on the inner side of the incident aperture diameter φd ₂₁₃ = 5.492 is reflected in the third lens L ₃ after refraction as the other light beam indicated by the arrow in FIG. In the direction away from the optical axis x ₁ x ₁ ′. Next, this case will be described.

As an example, here, consider a light ray incident at a position on the incident aperture φd ₂₁₄ = 4.000 mm. At this time, when the left side and the right side of the above equation (3) are obtained, the result is as follows.
Left side of equation (3) = arcsin (1 / n)
= Arcsin (1 / 1.83917)
= 32.937 °
(However, n = n ₅ )
Right side of equation (3) = arctan ((d 3/2) / √ {R 2 ^ 2- (d 3/2) ^ 2})
= Arctan ((4/2) / √ {5.05 ^ 2- (4/2) ^ 2})
= 23.331 °
(Where d ₃ = d ₂₁₄ , R ₂ = r ₅ ).

Therefore, the left side is greater than the right side, and the above formula (3) is satisfied. As a result, the angle formed between the light beam in the third lens L ₃ that is incident and refracted at a position on the incident aperture φd ₂₁₄ = 4.000 mm and the normal line of the curved surface at the incident position is the curved surface at the incident position. of greater than the angle between the normal line, light in the third lens L ₃ after refraction will proceed within the third lens L ₃ toward the direction away from the optical axis x ₁ x ₁ '.

Subsequently, the left side and the right side of the above equation (4) are obtained as follows.
Left = arctan of formula _{(4) [{(d 2} -d 3) / 2} / (t + √ {R 2 ^ 2- (d 3/2) ^ 2} -√ {R 2 ^ 2- (d 2 / 2) ^ 2})] + arcsin {(d 3/2) / R 2}
= Arctan [{(7.876-4) / 2} / (0.661 + √ {5.05 ^ 2- (4/2) ^ 2} -√ {5.05 ^ 2- (7.876 / 2) ^ 2})] + arcsin { (4/2) /5.05}
= 65.540 °
(Where d ₂ = d ₂₁₁ , d ₃ = d ₂₁₄ , t = t ₁ , R ₂ = r ₅ ).

Right side of equation (4) = arcsin (1 / n)
= Arcsin (1 / 1.83917)
= 32.937 °
(Where n = n ₅ ).

Therefore, the left side is greater than the right side, and the above formula (4) is satisfied. Thus, rays in the third lens L ₃ refracted incident on a position on the entrance aperture .phi.d ₂₁₄ = 4.000 mm, the progression of the third inner lens L ₃ toward the direction away from the optical axis x ₁ x ₁ ' Then, the inside of the optical surface having surface accuracy that satisfies the optical performance of the optical system on the exit surface of the third lens L ₃ is emitted.

As described above, according to the optical element 3 according to the present embodiment, similarly to Embodiment 1, light incident on the incident position to satisfy the above equation in the third lens L ₃ is an outer peripheral surface of the third lens L ₃ There is no direct travel, and there is no reflection on the outer peripheral surface. Therefore, the optical element 3 according to the present embodiment can achieve the same effects as the optical element 1 according to the first embodiment.

  As described above, the first and second embodiments have been described. In each of the embodiments, an aspherical lens having a positive refractive index having a convex curved surface on the incident surface side can be applied as the lens of the optical element. In this case, the approximate radius of curvature at the incident position may be applied as the radius of curvature of the curved surface at the incident position.

  Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and changes may be made without departing from the gist of the present invention.

1 is a partial cross-sectional view of an optical element according to Example 1. FIG. (a) is sectional drawing of the photographic lens which has an optical system containing the optical element which concerns on Example 2, Comprising: The figure which also showed a part of light ray which contributes to image formation, (b) is the optical It is sectional drawing of an element. It is sectional drawing of the imaging lens which has an optical system containing the optical element which concerns on Example 2, Comprising: It is the figure which also showed a part of light ray which passes the optical element. It is a partial cross section figure which shows an example of the conventional optical element comprised including the lens contained in an optical system, and the holding frame of this lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical element 2 Shooting lens 3 Optical element

Claims (3)

An optical element configured by integrating a plurality of lenses of an optical system composed of a plurality of lenses and a holding frame of the lenses,
The lens of the optical element has a positive refracting power whose convex surface on the incident surface side is convex,
In the lens of the optical element, a radius of curvature of the curved surface on the incident surface side at the incident position of the light beam is R ₁ , a diameter having a radius as a distance between the incident position and the optical axis is φd ₁ , and an outer diameter of the lens is φd _{2. When} the refractive index of the lens is n, within the maximum incident aperture of the light beam contributing to image formation,
arcsin (1 / n) ≦ arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}) (1),
and,
d ₁ <d ₂ (2),
Have a position of incidence of satisfying rays a
The optical element, wherein the light beam incident on the incident position is not irradiated to the holding frame that directly holds the lens of the optical element. In the lens of the optical element, in the formula (1),
arcsin (1 / n) = arctan ((d 1/2) / √ {R 1 ^ 2- (d 1/2) ^ 2}),
And an aperture whose diameter is the distance between the incident position of the light beam on the incident surface side curved surface and the optical axis, which is inside the aperture φd ₁ when satisfying the expression (2), is φd ₃ , Where R _{2 is} the radius of curvature at the incident position where the distance is the radius of the aperture φd ₃ , and t is the thickness in the optical axis direction at the outer periphery of the lens.
arcsin (1 / n)> arctan ((d 3/2) / √ {R 2 ^ 2- (d 3/2) ^ 2}) (3),
and,
_{arctan [{(d 2 -d 3} ) / 2} / (t + √ {R 2 ^ 2- (d 3/2) ^ 2} -√ {R 2 ^ 2- (d 2/2) ^ 2}) _{] + arcsin {(d 3/} 2) / R 2}> arcsin (1 / n) (4),
Having a light incident position satisfying
The optical element according to claim 1. In the lens of the optical element, the emission position of the light beam entering the maximum incident aperture when satisfying the expressions (1) and (2) is an optical surface having surface accuracy that satisfies the optical performance of the optical system. Is within,
The optical element according to claim 1.

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