JPH0616133B2 - Waterproof camera focus adjuster - Google Patents

Description

The present invention relates to a focus adjustment device for a waterproof camera capable of shooting underwater.

<Prior Art> A waterproof camera provided with an automatic focusing device is known.
Such a waterproof camera has the following problems. That is, as is well known, the amount of light from the subject decreases due to the absorption of sunlight in water, and the brightness of the subject becomes uniform due to the scattering of light, which also reduces the contrast of the subject. Detection and in-focus state determination are very difficult. In order to improve this, a method of projecting a spot-like visible ray on the subject to increase the contrast of the subject can be considered,
The amount of light reaching the subject is attenuated due to the presence of many floating substances in water between the camera and the subject and the above-mentioned light absorption, and it is difficult to obtain the contrast necessary for distance detection. Also, in an infrared light projection type distance measuring circuit, infrared light is absorbed in water and the reflected light is not obtained very much by the camera, and the object is located at infinity beyond a certain distance. Be misunderstood. When the visible light or the infrared light is projected onto the subject, the reflected light from the underwater floating matter may be received or the contrast thereof may be increased to obtain false distance information. Thus, in underwater photography, the distance measuring circuit and the focus state determination circuit cannot operate normally, and therefore,
It has the drawback of getting out-of-focus photographs by focusing on the wrong position.

Therefore, in addition to the automatic focus adjustment by the above-described automatic focus adjustment device, manual focus adjustment to a predetermined distance by manual operation can be performed, and one of these focus adjustments is selected. A switch is provided for automatic selection, and during normal shooting in air, this switch is set to the automatic side for automatic focus adjustment, and when shooting underwater, it is switched to the manual side for manual focus. It is conceivable to make adjustments. However, it is easy to forget to operate such a switching switch, and if underwater photography is performed with the switching switch being on the automatic side, the probability that an out-of-focus photograph will be obtained increases. Conversely, the same applies to the case where image pickup is performed in the air with the switching switch kept on the manual side.

As a solution to these drawbacks, JP-A-59-53
819 has been proposed.

This is based on one of the first signal and the second signal for controlling the lens position for the focus adjustment control member to focus the photographing lens automatically on the desired subject and at the predetermined distance. The camera is configured to perform focus adjustment, and which of the above focus adjustments is performed is controlled by a detection signal from a detection member that automatically detects whether the camera is in water or in air. The focus is adjusted based on the second signal when photographing underwater and based on the first signal when photographing in air.

This detection member is as shown in FIG. That is,
When the camera is in the air, the refractive index is 1 because the air above the detection window 21 is air. On the other hand, since the detection window 21 is made of methacrylic resin, its refractive index is 1.49.
Therefore, the critical angle α of methacrylic resin to air is The luminous flux of the light emitting element 22 that has entered the upper plane of the detection window 21 at an incident angle of 50 ° is totally reflected by the plane as shown by the solid line in the figure and enters the light receiving element 23. Next, when the camera is underwater, water is above the detection window 21 and its refractive index is usually about 1.33. Therefore, the critical angle β of water for methacrylic resin is The light flux of the light emitting element 22 that has entered the upper plane of the detection window 21 at an incident angle of 50 ° exits the camera as shown by the broken line in the figure, and the light of the light emitting element 22 enters the light receiving element 23. do not do. In any case, natural light may enter the light receiving element 23 from the outside of the camera, but the amount of incident light is negligible with respect to the amount of light emitted from the light emitting element 22. The member shall not be operable. In this way, it is detected that the camera is in the air when the light receiving element 23 receives the light from the light emitting element 22 and the camera is in the water when the light is not received.

Such a conventional waterproof camera requires a detection member for detecting whether water is in the air, which requires a light emitting element 22, a light receiving element 23, and a circuit for driving the light emitting element 22 and the light receiving element 23. It is expensive and will greatly increase the cost of the camera.

However, these are, in essence, those that operate only when the camera is submerged in water, and are completely unnecessary when shooting in the general air.For those who usually shoot underwater only a few times a year, It is very useless. Further, it is necessary to waterproof the dial for switching between automatic focus adjustment and manual focus adjustment and the detection window 21. For this reason, the number of waterproof parts is increased, which leads to a cost increase and a decrease in reliability of waterproofing. In addition, the dial allows you to set the distance by turning it, which seems convenient at first glance, but it is a contradiction that it is necessary to adjust the focus in the water even though the AF does not require the focus adjustment in the air. There is a feeling that I was feeling that, when the dial is set to the AF position, it is said that it will be fixed at a certain specific distance,
This may cause the user to feel that the AF is operating even in water. Further, with this dial, the user may make a mistake in determining that the focus can be manually set on land.

In addition, the light emitting element of the detection member may cause light emission failure, or the detection window 21 may be damaged, and the light of the light emitting diode may be detected by the detection window 2.
If the light is scattered on the upper plane of 1, the light receiving element 23 cannot receive the light, so it is determined that the camera is underwater and A
There was a risk that F would stop working.

<Objects of the Invention> The present invention has been made in view of the above circumstances, and shows a state of a light flux that passes through two optical paths that intersect with each other in front of a camera with a subject position as an apex and whose apex angle changes according to the subject distance. A focus adjustment device for a camera, which forms a focus adjustment signal by detecting, is disposed in at least one of the two optical paths, and does not substantially refract the optical path in air,
In water, there are provided optical means for refracting the two optical paths so that they do not intersect in front of the camera, and focus setting means for setting the focus state of the photographing optical means to a predetermined state in response to the fact that the state of the light flux cannot be detected. Thus, it is intended to provide a focus adjustment device for a waterproof camera which has a simple configuration and enables appropriate focus adjustment both in air and underwater.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire camera, where 1 is the camera body and 2
Is a camera back cover, 3 is a locking mechanism, 4 is a photographing lens window, 5
Is a relays lever, 6 is a strobe light emitting window, 7 is a finder window, 8 is a light projecting window for distance measurement, and 9 is a light receiving window.

The optical system of such a camera is as shown in FIG. 2 and FIG. That is, 10 is a taking lens, and 11 is a film surface. Reference numeral 12 denotes a light projecting lens for applying the light of the light emitting element 13 for distance measurement to the subject, and 14 denotes a light receiving lens for condensing the light of the light emitting element 13 returning to the subject on the light receiving element 15. The light projecting window 8 has its normal line inclined upward when viewed from the front of the camera. The normal line of the light receiving window 9 is parallel to the optical axis of the taking lens 10. Reference numeral 16 is a waterproof packing for the back cover 2.

The taking lens window 4 is formed in a concave surface, and the taking lens window 4 and the taking lens 10 form a taking optical system. This allows the shooting lens to focus when shooting underwater.
It is designed to shift toward the front compared to in the air.

That is, the photographing optical system is a first group of the first surface on the object side, a second group is the second surface and thereafter, the radius of curvature of the first surface is R ₁ , the radius of curvature of the second surface is R ₂ , and If the focal length of the second group is fII, (a) -90fII <R ₁ <-2.5fII (b) 0 <R ₁ > / R ₂ <23.4 The lens focus can be pulled closer to the front than the land lens focus (for example, a lens with a focus of 3 m on land can be 1.5 m in water).

Here, FIGS. 4 and 5 show the principle of the distance measuring system of the camera shown in FIGS. 1 to 3. In FIG. 4, the light emitted from the light emitting section G is a condensing lens for projecting light. The light passes through PL and is reflected by the object M, and the reflected near-infrared ray is received by the light receiving section R through the light receiving condenser lens RL. These lenses PL and RL are arranged apart from each other by a fixed base line length. The light receiving part R is fixed with the distance measuring zone in between.
The light emitting portion G is swung as shown by an arrow so that scanning is performed from the near side to the far side. Therefore, according to the principle of triangulation, the light emitting part G
The deflection angle and the distance to the object uniquely correspond to each other. The light beam projected by the optical system scans the distance measuring zone on the object plane in the base line direction. In this case, the distance-measuring zone may be considered to be the surface of the light-receiving unit R facing the object surface. The light receiving unit input has a curve as shown in FIG. 5 which has a peak at the time of combined distance measurement in which the zones of light projection and light reception match, so that the object distance can be measured by detecting this peak.

It is assumed that such a distance measuring system is incorporated in the camera. A window portion for distance measurement is provided for each of the light projecting lens PL and the light receiving lens RL.

Next, the operation of the above configuration will be described.
When it is in the air as shown in the figure, the autofocus mechanism works in exactly the same way as a normal camera, that is, the optical system for projecting and receiving light works in the same way as in FIG.

When the camera is underwater as shown in FIG. 2, the light emitted from the light projecting element 13 is refracted by the inclined light projecting window 8 and projected upward in the drawing, and the light is emitted to the light receiving element 15. Since the light receiving element 15 cannot receive the reflected light of the projected light because it does not hit the subject in the optical path of the collecting lens 14, an AF circuit (not shown) determines that the subject is at infinity, and the lens 10 Is released at a position where it focuses at infinity. At this time, the first surface of the taking lens window 4 in front of the lens 10 is a concave surface as described above, and when the lens 10 is at the infinite position, the best focus is obtained near 1.5 m in water.

In general, the refraction state of light when the light goes out of the air through the glass plate into the water will be described. In FIG. 6, n1, n
2 and n3 are the refractive indices of air, glass, and water, respectively, and n1 <n2 <n3 as described above. A ray A obliquely incident from the air is refracted into a ray indicated by A'in the glass plate and A "in water. The normal line of the glass sheet and the angles formed by these rays are α, α ', α", respectively. Then, equations (1) and (2) are established from the law of refraction.

n1sinα = n2sinα ′ (1) n2sinα ′ = n3sinα ″ (2) From the equations (1) and (2), the following equation (3) is established.

n1sinα = n3sinα ″ (3) If the refractive index n3 of water is the same as that n1 of air,
The light rays that emerge from the glass into the water travel at an angle α as shown by the dotted line, and are therefore parallel to the optical path in the air (dashed line). At this time, the optical paths in air and in water deviate by Δl, but since this amount is smaller than the thickness of the glass plate, it is usually negligible with respect to the subject distance. In this specification,
This Δl is ignored. Actually, the refractive index is n1 <n3 <n
Therefore, as shown by the solid line in FIG. 6, the optical path in air and the optical path in water are not parallel, and α> α ″. However, it tends to be closer to the normal direction of the glass plate.

In other words, if the projection window or the reception window for AF is tilted, it works as a normal AF camera in the air, it always measures infinity in water, and the one with the best focus at infinity The curvature of the first surface of the window can bring the best focus to around 1.5 m. However, even if the windows are tilted, if they are tilted so that the normals of these two windows intersect, the light of the light projecting element returns to the light receiving element 15 by being reflected by the suspended matter in the water or bubbles in the vicinity. It is not desirable because it may come.

Although the light projecting window is tilted with respect to the optical axis of the taking lens in the above-described embodiments, the light receiving window may be tilted, or both windows may be tilted. In other words, the normals of the two windows are not parallel and do not change in the front.

Further, when the window 8 is tilted as shown in FIG. 4, the tilted window 8 is likely to be rained, and the projected light rays are scattered by the water accumulated in the window, which may cause erroneous distance measurement. Therefore, in FIG. 7, by tilting the window 8 downward, the probability of erroneous distance measurement in the rain can be reduced.

In addition, the range that an amateur can usually go through is a water depth of 2 to 3 m.
If it is a sunny day in midsummer, it will be about EV14,
Although it depends on the program diagram, it is possible to narrow down considerably, and the camera equipped with a wide-angle lens as a standard has a sufficient depth of field, and it is possible to obtain sufficient shooting results even if it becomes a fixed focus camera underwater. It is a thing.

In the above-mentioned embodiment, both or one of the light projecting window 8 and the light receiving window 9 corresponds to the optical means of the present invention, and the AF circuit and the taking lens window 4 not shown correspond to the setting means of the present invention.

<Effects of the Invention> As described above, according to the present invention, in a focus adjustment device for a waterproof camera, it functions like an ordinary automatic focus adjustment device in the air with a simple configuration, and automatically underwater photography in water. Therefore, it is possible to provide a focus adjustment device for a waterproof camera that can perform a suitable focus adjustment in both air and water at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of a waterproof camera showing one embodiment of the present invention,
2 and 3 show the optical configuration of FIG. 1, FIG. 2 is an explanatory view of optical paths in water, FIG. 3 is an explanatory view of optical paths in air, and FIG. 4 is FIGS. FIG. 3 is a principle diagram of a camera distance measuring system, FIG. 5 is an output curve diagram of FIG. 4, FIG. 6 is a diagram for explaining a refraction state when light goes out from the air into water, and FIG. FIG. 8 is a diagram showing a modified example of FIG. 3, and FIG. 8 is a configuration diagram of a detection means used in a conventional waterproof camera. 1 ... Camera body, 4 ... Shooting lens window, 8 ... Emitter window, 9 ... Light receiving window, 10 ... Shooting lens, 12 ... Emitter lens, 13 ... Light emitting element, 14 ... Light receiving lens , 15
……Light receiving element.

Claims (1)

[Claims] 1. A focus adjustment of a camera which forms a focus adjustment signal by detecting a state of a light flux passing through two optical paths which intersect with each other in front of the camera with a subject position as an apex and whose apex angle changes according to the subject distance. In the device, an optical unit that is disposed in at least one of the two optical paths and that does not substantially refract the optical paths in air and refracts the two optical paths in water so as not to intersect in front of the camera, A focus adjusting device for a waterproof camera, comprising: focus setting means for setting the focus state of the photographing optical means to a predetermined state in response to the state being undetectable.