JPH06250274A - Amphibian camera - Google Patents

Abstract

PURPOSE:To provide the camera with which photographing is possible both in the water and in the air by constituting a photographic optical system in such a manner that a negative distortion aberration is generated at the time of use in the air so as to generate a negative magnification chromatic aberration forming an image at a point nearer the optical axis with the shorter wavelength light with respect to offaxial luminous fluxes. CONSTITUTION:A camera body 1 is housed in a waterproof case 3 integral with a waterproof plate 2 on the front face of the lens. The photographic optical system is composed, successively from an object side, of the plate 2, a diaphragm 6 and a positive mechanical lens 4, the concave face of which is directed to the object side. The radius of curvature on the object side face of the mechanical lens, defined as r, the focal length, as f, the distance between the diaphragm and the lens, as x, and the axial thickness of the mechanical lens, as t, are so set as to satisfy 0.3<¦r¦/f<1.5; 0.05<x/f<0.2; 0.02<t/f<0.1. The one face of the mechanical lens is preferably formed as an aspherical face so that the refracting power of the lens is stronger toward the outer peripheral part of the lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera which can be used both in water and in the air, and a construction of a photographing optical system thereof.
Particularly, the present invention relates to a lens system having a simple structure used for a film with a lens or the like.

[0002]

2. Description of the Related Art Conventionally, what is called an underwater camera includes one made exclusively for underwater photography and one used with an ordinary camera put in a waterproof case. An underwater camera using a film with a lens or the like has the latter structure because of the structure of the product, and a normal product used in the air is put in a special waterproof case so that it can be used in the water. However, the taking lens used in a normal product is a rear diaphragm lens as shown in FIG. If you put this in a waterproof case and use it in water, the waterproof plate will be positioned in front of the lens system, but when shooting in water, unlike in air, the refractive index before and after the waterproof plate is different, The oblique rays emitted from are refracted. Therefore, the positive distortion becomes large during underwater photography. Also, due to the dispersion of water, the shorter the wavelength of light, the greater the refraction,
The shorter the wavelength of light, the greater the positive chromatic aberration of magnification that forms an image at a position farther from the optical axis. As a result, as shown in FIGS. 10 and 11, lateral chromatic aberration and positive distortion become large, which is not preferable. Such a tendency is a drawback that occurs not only in a taking lens composed of a single lens but also in a taking lens having a simple structure.

[0003]

SUMMARY OF THE INVENTION The present invention is a camera and a lens for a camera which can be photographed both in water and in the air, and have good performance in both usage conditions, and particularly chromatic aberration of magnification and distortion are corrected well. To provide what was done. In particular, it is to provide an inexpensive amphibious camera such as a film with a lens.

[0004]

A camera according to the present invention is an airtight camera in which a waterproof plate having almost no refracting power is arranged on the most object side of a photographing optical system, and the photographing optical system is It is characterized in that negative distortion occurs when it is used in air, and negative lateral chromatic aberration occurs in which an off-axis light beam forms an image at a position closer to the optical axis for shorter wavelength light.

When the image forming system is a single lens, the photographing optics are sequentially arranged from the object side to the waterproof plate, the diaphragm, and
It is composed of a positive meniscus lens with a concave surface facing the object side. When the radius of curvature of the object side surface of the positive meniscus lens is r and the focal length is f, the following conditions are satisfied. 0.3 <| r | / f <1.5 (1) Further, when the distance between the diaphragm and the lens is x, the following condition is satisfied. 0.05 <x / f <0.2 (2) Further, when the axial thickness of the meniscus lens is t, the following condition is satisfied. 0.02 <t / f <0.1 (3)

Further, it is desirable that at least one surface of the meniscus lens is an aspherical surface, and the refracting power of the lens becomes stronger as it goes from the optical axis to the outer peripheral portion of the lens. Specifically, when the object side surface of the meniscus lens is an aspherical surface, the aspherical surface is such that the absolute value of the radius of curvature increases from the optical axis of the first surface toward the lens outer periphery, and the image side surface When is an aspherical surface, the aspherical surface is such that the absolute value of the radius of curvature becomes smaller from the optical axis toward the lens outer circumference.

[0007]

[Function] When aberration correction is performed so that negative distortion occurs when used in air and negative lateral chromatic aberration occurs for light of short wavelength, positive distortion generated when used in water The positive chromatic aberration of magnification can be canceled out to prevent the deterioration of the aberration during use in water, and the lateral chromatic aberration and the distortion in air can be balanced. If a positive lens is arranged behind the diaphragm, negative distortion will occur, and negative lateral chromatic aberration will occur with respect to light of a short wavelength. If the lens is a meniscus lens with a concave surface facing the object side, the outward coma aberration can be reduced and the meridional image plane can be prevented from becoming too underexposed.

Next, the conditional expression will be described. Conditional expression (1) is a condition for determining the shape of the meniscus lens, and if the lower limit of the conditional expression is not reached, spherical aberration becomes large and inward coma becomes large. On the contrary, when the value exceeds the upper limit, the outward coma becomes large and the field curvature becomes under. If the lower limit of conditional expression (2) is exceeded, the outward coma will be large and the field curvature will be under. When the value exceeds the upper limit, inward coma becomes large and the meridional image plane becomes over, resulting in an increase in astigmatism. If the lower limit of conditional expression (3) is exceeded, negative chromatic aberration of magnification and negative distortion will be small in the air, but positive lateral chromatic aberration and positive distortion will be too large during use in water, which is not preferable. Conversely, conditional expression (3)
If the upper limit of the above is exceeded, negative lateral chromatic aberration in the air becomes too large, which is not preferable.

If at least one surface of the meniscus lens is an aspherical surface and the positive refracting power becomes stronger from the optical axis of the lens toward the outer peripheral portion, the astigmatism is corrected while the coma aberration is corrected well. Can be made smaller. Even if the object-side surface of the meniscus lens is an aspherical surface whose absolute value of the radius of curvature increases as it goes from the optical axis to the lens outer peripheral portion,
Even if the image-side surface of the meniscus lens is an aspherical surface in which the absolute value of the radius of curvature becomes smaller as it goes from the optical axis toward the outer peripheral portion of the lens, the same effect can be obtained.

[0010]

EXAMPLES Examples of the present invention will be shown below. The symbols in the table indicate the following. r: radius of curvature of refraction surface d: distance between refraction surfaces nd: refractive index of lens material νd: Abbe number of lens material F: F number ω: half angle of view Further, the aspherical surface shape of the present invention is X in the optical axis direction. When the direction perpendicular to the axis and the optical axis is the Y axis, it is expressed by Equation 1.

[Equation 1] Here, r is a paraxial radius of curvature, and K and A ₂ i are aspherical coefficients. In the table, "*" is attached to the aspherical surface.

Example 1 f = 30 F = 9.5 ω = 38 ° (in air) Surface No. rd nd vd 1 ∞ 1.50 1.492 57 2 ∞ 1.00 3 (diaphragm) ∞ 3. 50 * 4 −16.000 1.50 1.492 575 −7.915 4th surface aspherical coefficient K = −1.8 A ₂ i = 0 (i = 2, 3, 4 ...) | r | /F=0.53 x / f = 0.12 t / f = 0.05

Example 2 f = 30 F = 9.5 ω = 38 ° (in air) Surface No. rd nd νd 1 ∞ 1.50 1.492 57 2 ∞ 1.00 3 (aperture) ∞ 4. 00 4 -20.000 1.50 1.492 57 * 5 -8.703 5th surface aspherical surface coefficient K = 0.15 A ₂ i = 0 (i = 2, 3, 4 ...) | r | / f = 0.67 x / f = 0.13 t / f = 0.05

Example 3 f = 30 F = 9.5 ω = 38 ° (in air) Surface No. rd nd νd 1 ∞ 1.50 1.492 57 2 ∞ 1.00 3 (aperture) ∞ 3. 50 4 -20.000 1.50 1.492 575-8.703 | r | /f=0.67 x / f = 0.12 t / f = 0.05

In the above embodiments, good performance can be obtained by curving the image plane toward the lens side in the long side direction of the screen like a cylindrical shape. In the case of a cylindrical structure, a radius of curvature of about 100 is suitable in this embodiment. Further, in the above-mentioned embodiments, the waterproof plate is a plane-parallel plate having two flat surfaces, but it may be bent into a meniscus shape if the refracting power is substantially zero. FIG. 8 shows a configuration example of the camera. In this embodiment, the camera body 1
Is contained in a waterproof case 3 integrated with the waterproof plate 2 on the front surface of the lens. The taking lens 4 may be any one of the above-mentioned embodiments, and the image forming surface 5 is curved in the long side direction of the screen in a cylindrical manner. Reference numeral 6 is a diaphragm, and 7 is a shutter plate.

[0015]

As shown in the sectional view and the aberration diagram of the embodiment, the amphibious camera of the present invention has a simple structure, and even in the case where the aspherical surface is not used, not only the normal photographing in the air but also the underwater photographing is performed. Even in the case of photographing at 1, the distortion and the chromatic aberration of magnification are corrected to be small, and other aberrations are sufficiently corrected, so that the imaging performance is excellent. Further, since no special operation or mechanism is required for photographing in air and photographing in water, the structure is simple, the reliability and durability are high, and the film can be provided at low cost, which is suitable for a lens-equipped film or the like. Further, although the waterproof case is used in the embodiment, it is easy to make the box body of the film with lens have a waterproof structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical system of an amphibious camera of the present invention.

FIG. 2 is an aberration diagram of Example 1 of the optical system of the amphibious camera of the present invention, showing in air.

FIG. 3 is an aberration diagram of Example 1 of the optical system of the amphibious camera of the present invention, which shows underwater.

FIG. 4 is an aberration diagram of Example 2 of the optical system of the amphibious camera of the present invention, showing the state in the air.

FIG. 5 is an aberration diagram of Example 2 of the optical system of the amphibious camera of the present invention, which shows underwater.

FIG. 6 is an aberration diagram of Example 3 of the optical system of the amphibious camera of the present invention, showing in the air.

FIG. 7 is an aberration diagram of Example 3 of the optical system of the amphibious camera of the present invention, which shows underwater.

FIG. 8 is a cross-sectional view showing an example of the configuration of the amphibious camera of the present invention.

FIG. 9 is a cross-sectional view of a conventional film optical system with a waterproof lens.

FIG. 10 is an aberration diagram of a configuration example of a conventional film optical system with a waterproof lens, showing in the air.

FIG. 11 is an aberration diagram of a configuration example of a conventional film optical system with a waterproof lens, showing underwater.

[Explanation of symbols]

1 Camera body 2 Waterproof plate 3 Waterproof case 4 Photographing lens 5 Image plane 6 Aperture 7 Shutter plate

Claims (8)

[Claims] 1. A camera having an airtightness in which a waterproof plate having almost no refracting power is disposed on the most object side of the photographing optical system, and the photographing optical system causes negative distortion when used in air. In addition, the amphibious camera is characterized in that, with respect to the off-axis light flux, negative wavelength chromatic aberration is formed so that light having a shorter wavelength is imaged closer to the optical axis. 2. A camera having airtightness in which a waterproof plate having almost no refracting power is arranged on the most object side of the photographing optical system, and the photographing optical system has the waterproof plate, a diaphragm, and an aperture in order from the object side. The amphibious camera according to claim 1, wherein the amphibious camera has a positive meniscus lens having a concave surface facing the object side. 3. The amphibious camera according to claim 2, wherein the following conditions are satisfied, where r is a radius of curvature of the object side surface of the meniscus lens, and f is a focal length thereof. 0.3 <| r | / f <1.5 4. The following conditional expression is satisfied, where x is the distance between the diaphragm and the lens.
Amphibious camera described. 0.05 <x / f <0.2 5. The amphibious camera according to claim 4, wherein the following condition is satisfied, where t is the axial thickness of the meniscus lens. 0.02 <t / f <0.1 6. The meniscus lens has at least one surface that is an aspherical surface, and the aspherical shape has a positive refractive power that increases from the optical axis portion of the lens toward the outer peripheral portion. Amphibious camera described in 5. 7. The object-side surface of the meniscus lens,
The amphibious camera according to claim 5, wherein the amphibious camera has an aspherical surface such that the absolute value of the radius of curvature increases from the optical axis toward the outer peripheral portion of the lens. 8. The image-side surface of the meniscus lens is an aspherical surface such that the absolute value of the radius of curvature becomes smaller as it goes from the optical axis to the outer peripheral portion of the lens.
Amphibious camera described.