Photography – Underwater – waterproof – or water-resistant camera – Having illumination device
Reexamination Certificate
2001-07-25
2003-01-28
Perkey, W. B. (Department: 2851)
Photography
Underwater, waterproof, or water-resistant camera
Having illumination device
C396S267000, C396S431000
Reexamination Certificate
active
06512887
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a flash lamp for underwater photography provided with a so-called target light (to be defined more precisely below), as well as methods and devices for controlling the emission of light from such a target light.
For underwater photography, divers have been carrying along a single-lens reflex camera inside a water-proof housing together with a group of exchange lenses, but a flash lamp is nearly indispensable in underwater photography both because red light is more easily absorbed by water to cause a color imbalance and because there is usually not enough natural light available. As shown in
FIG. 1
, an underwater flash lamp
90
is usually attached to a camera
91
by means of a flexible arm
92
and is positioned away from the camera
91
. One of the reasons for this is that the axis of emitted light from the flash lamp
90
must be displaced (both in terms of position and angle) from the optical axis of the camera
91
because there are usually many small objects such as plankton and grains of same floating inside the water around the underwater photographer. If the flash lamp
90
were set near the camera
91
, its light would be strongly reflected by these small objects in front of the target object intended to be photographed and the resulting picture would look like that of a snow scene. Another reason is that underwater photography depends nearly entirely on the light from the flash lamp and hence the position and orientation of the flash lamp should be freely changeable, depending on the desired light condition as well as that of the target object to be photographed.
In underwater photography, the position and orientation of the flash lamp
90
at the end of the flexible arm
92
are adjusted after each exposure in order to get ready for the next opportunity. At the same time, the photographer must check whether the flash lamp
90
is indeed pointing in the direction of the target object to be photographed. Since the visual sense of distance is different in the underwater condition from that in the above-water condition, it is a troublesome work to adjust and check the direction of the optical axis of an underwater flash lamp.
Experienced underwater photographers have learned to attach a penlight
94
, as shown in
FIG. 1
, in order to make this work somewhat easier. Since the penlight
94
is preliminarily attached to the flash lamp
90
such that their optical axes coincide approximately, the underwater photographer can predict the reach of the optical axis of the flash lamp
90
by switching on the penlight
94
. This method of attaching a penlight, however, has the following problems:
(1) With the penlight attached, the underwater camera system as a whole becomes bulkier and heavier;
(2) The flux of light emitted from the penlight tends to expand and is likely to be sensed by the fish, which will react and swim away;
(3) Since the flux of light emitted from the penlight expands, it becomes weak by the time it reaches the neighborhood of the target object to be photographed and its direction cannot be ascertained easily by the photographer wearing a goggle;
(4) The penlight requires a bulb with a large output power so as to be effective in the underwater environment and this adversely affects the useful lifetime of the batteries;
(5) Since the batteries for the penlight and for the flash lamp have different lifetimes, it is troublesome to dependably manage them of both; and
(6) It is troublesome to control its operation because it must be switched off before the camera is clicked so as to prevent the light from the penlight from entering the camera.
Although underwater flash lamps incorporating a small light source inside are coming to be available, they can merely serve to simplify the management of batteries somewhat and the problems listed above are mostly unsolved.
Since the underwater photographer usually remains in one position and waits for a right moment to click the shutter while looking into the finder through the goggle, it is desirable to be able to ascertain the condition of the flash lamp without changing the body position and while continuing to look through the finder. In general, the condition of the camera of an underwater photography system (say, a single-lens reflex camera) can be ascertained by means of a display marker which is made visible inside its finder. Since the condition of the flash lamp cannot generally be ascertained merely by looking into the finder, the photographer will have to change the body position, even if temporarily, in order to turn around the system as a whole for checking the display of an LED, for example, on the side surface of the flash lamp for displaying the charge condition, etc. There is usually a current at the site of underwater photography, and the ground condition may not be convenient for the photographer to stand up comfortably or to keep the body in balance. Thus, a heavy labor is involved in moving around the equipment and changing the body position, and an extreme care must be taken.
When a digital cameral placed inside a waterproof housing is used for underwater photography, a flash lamp is sometimes attached to the exterior of the housing because such a housing is likely to interfere with the light from an internally provided flash lamp and the amount of effective light may be thereby diminished. In such a case, a light source, not the flash lamp itself, is sometimes used for assisting the user in focussing the camera because a digital camera is sometime more difficult to focus that a single-lens reflex camera. Such a light source may also serve the purpose of allowing the user to ascertain the position of the target object to be photographed or of illuminating the target object to be photographed for making its image on a liquid crystal display device brighter. Throughout herein, such a light source, not a flash lamp, provided for these and other purposes are referred to, in a broad sense of the expression, as a target light.
FIG. 2
shows an example of timing chart for the control of light emission from such a light source (the target light) for a flash lamp adapted to emit flash light preliminarily first and then for the second time as the main emission. When the shutter button is clicked, the flash lamp undergoes a preliminarily light emission before the shutter is opened and the reflected light is instantaneously measured for determining the quantity of light to be projected by the main emission. In this example, the target light remains turned on until the shutter is opened and is switched off in synchronism with the signal through the so-called X-contact (that is, the point where a signal for opening the shutter is transmitted), that is, simultaneously with the starting of the main emission of the flash lamp. If the flash lamp is of the type which undergoes only the main light emission (or the so-called “auto-stroboscopic” or “flashmatic-type”), there is no preliminary emission and the main emission is adapted to be carried out with a suitable exposure. In this case, too, the target light is switched off in synchronism with a signal through the X-contact.
This prior art method of controlling the timing for switching off a target light has the following problem. Since the shutter for a digital camera operates more slowly than that of an ordinary single-lens reflex camera (indicated by the slope of the curve for the shutter position in FIG.
2
), digital cameras are designed, in view of the fluctuations in the time required for the shutter to open completely, such that the X-contact will be switched on slightly after the shutter is completely opened. As a result, it sometimes happens that the target light stays switched on even after the shutter has begun to open until the main emission from the flash lamp is started (shown as time period t
a
in FIG.
2
), allowing its light to enter the camera through its lens and adversely affecting the quality of the picture taken.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an im
Inoue Akihide
Takematsu Yoshiyuki
Beyer Weaver & Thomas LLP
Perkey W. B.
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