JPS6365402A - Photographing lens for underwater camera - Google Patents

Abstract

PURPOSE:To automatically attain proximity setting with a simple structure at the time of underwater photographing by arranging a transparent flexible member in front of a lens so that the member is deflected by water pressure at the time of underwater photographing. CONSTITUTION:The transparent flexible member 2 is arranged in front of the photographing lens 1, the front face 2a side of the member 2a is exposed and the rear face 2b side is water-proofed so that the member 2 is deflected like a recessed surface by water pressure at the time of underwater photographing. Since water pressure is applied to the front face 2a of the member 2 and the rear face 2b is water-proofed at the time of underwater photographing, the front face 2a is deflected to the object side so as to be recessed by the pressure difference. Thereby, proximity setting can be automatically attained under water. Since the water pressure is increased in accordance with deeper dive, the deflection of the member 2 is also increased and the radius of curvature of the recessed surface is reduced, so that the degree of proximity setting is increased at a deep position to which light can not be easily projected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photographing lens for an underwater camera that automatically sets the proximity setting during underwater photographing.

(Prior Art) In general, in an amphibious camera, the focusing distance is longer in water than in the air due to the difference in refractive index between water and air in front of the photographic lens. In response to this, it has been proposed to make the front surface of the photographing lens concave (Japanese Patent Laid-Open No. 60-2971
Publication No. 7, JP-A-60-150039, JP-A No. 4
7-42173), this allows the focusing distance in water to be closer than in the air for a range farther than the center of curvature of the concave surface.

(Problem to be solved by the invention) With amphibious cameras, the AF function does not work when taking pictures underwater, and the shooting lens is set to position ■, but since visibility is poor underwater, it is difficult to take pictures at long distances. Therefore, it is more convenient to set the camera at a suitable short distance (for example, one or two wheels).Therefore, as in the prior art described above, underwater photography takes advantage of the difference in the refractive index of water and air. Sometimes automatic proximity settings are proposed. However, in this conventional technique, since the curvature of the concave surface on the front surface of the photographing lens is fixed, there is a problem in that the degree of proximity setting during underwater photography cannot be changed.

In other words, when shooting underwater, the deeper you dive to -a, the harder it is for the light to reach you, so it would be better to increase the close-up setting. However, the degree of proximity setting is the same in both cases, and there is a problem that the degree of proximity setting cannot be increased depending on the water depth. Furthermore, since the field of view during underwater photography changes depending on the transparency of the water and the strength of sunlight, it is preferable to be able to adjust the degree of close-up setting when taking underwater photographs. It was difficult to change.

The present invention has been made in view of these points, and its purpose is to provide a simple structure for underwater photography by arranging a transparent flexible member on the front surface of the lens and bending it under water pressure during underwater photography. Proximity can be set automatically when shooting,
Another object of the present invention is to provide a photographic lens for an underwater camera that can automatically increase the degree of proximity setting depending on the depth of the water.

(Means for Solving the Problems) In the photographing lens for an underwater camera according to the present invention, as shown in the attached drawing, a transparent flexible member 2 is disposed in front of the photographing lens 1, and during underwater photography, The front surface 2a of the transparent flexible member 2 is configured such that the transparent flexible member 2 is bent into a concave surface under water pressure.
The side is exposed and the rear surface 2b side is waterproof.

(Function) In the present invention, during underwater photography, the front surface 2a of the transparent flexible member 2 receives water pressure, and the rear surface 2b is waterproof. Therefore, due to this pressure difference, the front surface 2a is bent so as to be concave toward the subject, and therefore, the front surface 2a can be automatically set close to the subject underwater. Furthermore, as the water pressure increases as you dive deeper, the deflection of the transparent flexible member 2 also increases and the radius of curvature of the concave surface becomes smaller. Therefore, in deep water where it is difficult for light to reach, the proximity setting is automatically performed. The degree of

(Example) Examples of the present invention will be described below.

1121 and 2 are cross-sectional views of essential parts of an underwater camera photographing lens according to an embodiment of the present invention. In this embodiment, the photographing window 5 in the waterproof case 4 housing camera book #3 A transparent flexible member 2 is attached to the portion. The transparent flexible member 2 is made of a thin film of silicone rubber, and its outer periphery is airtightly attached to the waterproof case 4 by a pressing member 6. Since the transparent flexible member 2 is held in a tight structure with respect to the waterproof case 4, it can also serve as a backing. The transparent flexible member 2 is fixedly held in a planar shape, and maintains the planar shape on land as shown in FIG. A photographing lens 1 made of a combination of a plurality of optical glasses is disposed in a camera body 3 at a position corresponding to a photographing window 5. Photography lens 1
A film chamber 7 is provided at the rear of the camera. The back cover 8 of the waterproof case 4 is attached to the rear of the film chamber 7, and the contact portion between the back 118 and the waterproof case 4 has a waterproof structure.

When taking pictures underwater, water pressure is applied to the waterproof case 4,
As shown in FIG.
In this embodiment, the transparent flexible member 2 is in the form of a thin film;
Surface 2m' and surface 2b' shown in FIG. 2 have approximately the same radius of curvature. Therefore, the front surface 2m' of the transparent flexible member 2
With water in contact with the rear surface 2b' and air in contact with the rear surface 2b', the member 2
A convex lens is formed at this point, and the focusing distance of the photographic lens 1 becomes short.

FIG. 3 is an explanatory diagram for explaining that the focal length of the photographic lens is shorter underwater than on land. On land, the inside and outside of the waterproof case 4 have the same refractive index, and the transparent flexible member 2 is parallel and has no refractive power. 2b undergoes a reverse refraction action, and the light eventually enters the photographic lens 1 at the same angle as the angle of the light ray from the object point C, and is imaged on the film plane F. This relationship holds true even when the light travels backwards from the film surface to the object point. However, in water, the refractive index of water in contact with the front surface 2a1 of the transparent flexible member is
The refractive index is higher than that of the air inside the waterproof case 4 in contact with the rear surface 211', and the transparent flexible member 2 is concave toward the subject. If we consider that the light travels backwards from the film surface F in this state, the light rays emitted from the photographic lens 1 first reach the surface 2b'
The member 2 as a whole receives a positive refraction action, and then receives a negative refraction action at the surface 2a' because the difference in refractive index between the member 2 and water at the surface 2a'' is small. As a result, the reversed light ray reaches a point C' which is closer than the object point C. That is, an image of the point C° is formed on the film plane F.

In areas where the water is deeper, the water pressure applied to the transparent flexible member 2 increases, and as shown in the characteristic diagram of FIG.
Since the radius of curvature of ', 2b' becomes smaller, the focal length becomes even shorter. In Fig. 4, the horizontal axis represents water depth (water pressure), the vertical axis represents the reciprocal of the radius of curvature, and A represents the transparent flexible member 2.
This shows the characteristics when the film thickness is thick and the elastic modulus is small, and the characteristics when the mouth film is thin and the elastic modulus is large. Also,
C. On land, the transparent flexible member 2 is not flat,
This shows the characteristics when the lens has a curvature, and by using such characteristics, it becomes possible to set a desired focal length at a desired water depth.

FIG. 5 is a cross-sectional view of a main part of another embodiment of the present invention. In this embodiment, the front surface 2a and rear surface 2b of the transparent flexible member 2 are convex toward the subject in their natural state. When a predetermined force or more is applied to the front surface 2a of the transparent flexible member 2, the transparent flexible member 2 is held in a snap-action configuration so that the concave side faces the subject. When the above-mentioned force is removed, the elasticity of the blade returns to the state where the convex surface faces the subject. Underwater, the front surface of the transparent flexible member 2 is pushed by water pressure with a force greater than the predetermined value, so the front surface 2a' and the rear surface 2b' are concave toward the subject, and as in the case of the previous embodiment, the front surface of the transparent flexible member 2 is pressed at a close distance. will focus on. In this embodiment, the shape of the transparent flexible member 2 with its convex surface facing the subject and the shape of the concave surface facing the subject are determined by the member 2 itself, and water pressure is more important than determining the shape of the concave surface. Rather, it serves to cause a change in the state of the snap action, and therefore it is easier to determine the shape of the concave surface than if the balance between water pressure and the flexibility of the member 2 creates the shape of the concave surface.

FIG. 6 is a sectional view of a main part of still another embodiment of the present invention. In the configuration shown in FIG. 6, the transparent flexible member 2 has the function of a concave lens. Further, in this embodiment, the tension state of the transparent flexible member 2 can be changed manually. That is, by rotating the tightening ring 9 screwed onto the photographing window 5 of the waterproof case 4 and adjusting the position W back and forth, the tension state of the transparent flexible member 2 is changed. As a result, the amount of deflection of the member 2 changes even when the same water pressure is applied, so the power at the member 2 underwater can be adjusted. Specifically, when the tightening ring 9 is moved to the side of the waterproof case 4, the outer periphery of the transparent flexible member 2 is pressed by the pressing step 10 of the tightening ring 9, and the tension of the member 2 becomes stronger. , the amount of displacement of surfaces 2a and 2b due to water pressure becomes smaller. This can reduce the degree to which they become close underwater. To increase the degree of proximity, the tightening ring 9 is rotated in the opposite direction to weaken the tension of the member 2 so that the surfaces 2m and 2b are more flexible against the same water pressure.

FIG. 7 is a sectional view of a main part of another embodiment of the present invention. In this embodiment as well, the tension state of the flexible member 2 can be changed manually as in the embodiment of FIG. 6. It is configured so that it can be done. In this FIG. 7 embodiment, the waterproof case 4
A rigid retaining ring 11 is interposed between the tightening ring 9 screwed onto the photographing window 5 and the outer circumference of the transparent flexible member 2, and the surface opposite to the retaining ring 11 is waterproof. A ring-shaped pressing protrusion 12 is provided protruding from the case 4.

When the tightening ring 9 is moved to the side of the waterproof case 4, the outer circumference of the transparent flexible member 2 is compressed by the holding ring 11 that contacts the tightening ring 9 and the pressing protrusion 12 of the waterproof case 4, and the transparent flexible member 2 is pressed. The tension state of the flexible member 2 becomes stronger.

Although not shown, it is also possible to provide the transparent flexible member 2 with a convex lens effect.

In addition, a planar transparent flexible member 2 like the embodiment in FIG.
Even in those that use JJ! Naturally, by weakening the degree of deformation of the transparent flexible member 2 due to water pressure, the degree of deformation of the transparent flexible member 2 due to water pressure can be increased, as in the embodiments of FIGS. 6 and 7, and the degree of proximity setting can be increased. .

(Effects of the Invention) As described above, in the present invention, a transparent flexible member is disposed in front of the photographing lens, and the front surface of the transparent flexible member is bent into a concave surface under water pressure during underwater photography. Since the rear side of the transparent flexible member is waterproofed, during underwater photography, the transparent flexible member bends in a concave manner toward the subject due to water pressure. therefore,
The effect is that you can automatically set the proximity underwater,
In addition, as water pressure increases as you dive deeper, the deflection of the transparent flexible member also increases and the radius of curvature of the concave surface becomes smaller.For this reason, the proximity setting is automatically set in deep water where it is difficult for light to reach. It has the effect of increasing the intensity.

In addition, if the tension of the transparent flexible member is adjustable,
Since the degree of deflection due to water pressure can be adjusted, the degree of underwater proximity setting can be arbitrarily changed.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 and 2 are sectional views of essential parts of a photographic lens according to an embodiment of the present invention, and FIGS. 3 and 4 are explanatory views of the same operation.
FIG. 5 is a sectional view of a main part of another embodiment of the present invention, FIG. 6 is a sectional view of a main part of still another embodiment of the invention, and FIG. 7 is a sectional view of a main part of another embodiment of the invention. It is a diagram. 1 is a photographic lens, 2 is a transparent flexible member, 2a is a front surface, 2
b is the rear surface.

Claims (4)

[Claims] (1) A transparent flexible member is arranged in front of the photographic lens, and the front side of the transparent flexible member is exposed and the rear side is exposed so that the transparent flexible member bends concavely under water pressure during underwater photography. A waterproof lens for underwater cameras. (2) The photographing lens for an underwater camera according to claim 1, wherein the transparent flexible member is in the form of a thin film. (3) The photographing lens for an underwater camera according to claim 1, wherein the transparent flexible member is provided in a photographing window of a waterproof case housing the camera. (4) The photographing lens for an underwater camera according to claim 1, wherein the transparent flexible member has a tension that can be freely adjusted.