Photography – Flash system responsive to focal length or distance – Illumination angle responds to focal length or distance
Reexamination Certificate
2001-01-22
2003-02-11
Adams, Russell (Department: 2851)
Photography
Flash system responsive to focal length or distance
Illumination angle responds to focal length or distance
C396S175000
Reexamination Certificate
active
06519418
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a flash light emitting part arranged to vary the luminous intensity distribution angle thereof in association with a magnification varying action of a photo-taking lens.
2. Description of Related Art
Compact and lightweight cameras having built-in flash devices have been popularly in use. Most of the so-called compact cameras which are designed mainly for taking snapshots have built-in flash devices.
In these days, many of such compact cameras are provided also with zoom lenses for the purpose of improving the function thereof. As a result, many of the built-in flash devices of such cameras have come to be arranged to emit a large quantity of light to make light emission reachable a farther distance. For this purpose, either the size of the capacitor of a light emission circuit is increased or the flash device is arranged to be zoomed to make the light quantity distribution apposite to each of variable focal lengths of the photo-taking lens. The flash device of this type hereinafter will be called a built-in zoom flash device.
For example, a camera having a built-in zoom flash device in combination with a zoom lens, as disclosed in Japanese Patent No. 2662969, is provided with a magnification varying lens group to enable a photo-taking lens to perform a zooming action. When the magnification varying lens group is driven by a zoom motor, a cam plate is driven to the right or left in association with the movement of a gear provided at the magnification varying lens group. Then, the flash device is caused to perform a zooming action along a cam surface formed on the cam plate.
Another camera of the kind having a built-in zoom flash device, as disclosed in Japanese Laid-Open Patent Application No. Hei 11-212143, has a lens driving gear formed integrally with the driving tube of a zoom photo-taking lens and disposed at the last stage of a driving system gear train for the zoom photo-taking lens. In combination with the lens driving gear, a cylindrical cam is provided for driving an illumination angle varying member of the zoom flash device and is arranged at the last stage of a driving system gear train for the flash device. These gear trains are arranged to be driven respectively by driving motors.
In each of these cameras as mentioned above, the lens barrel mechanism is composed of a zoom mechanism part and a focusing mechanism part which are arranged separately from each other. Therefore, the flash device can be zoomed to obtain a light quantity distribution apposite to each focal length without any problem by simply interlocking the flash device with the zoom mechanism part.
However, in order to have the zoom mechanism part separately arranged from the focusing mechanism part, it is necessary in general to provide a lens group for a focusing action within the zoom mechanism part and to arrange the focusing mechanism part to drive the focusing lens group with a drive source which is provided solely for that purpose. This arrangement makes the lens barrel mechanism complex to cause an increase in cost. In addition to that, since the focusing mechanism part is disposed within the lens barrel, the size of the lens barrel is caused to increase.
To solve the above problem, the so-called stepped zoom lens barrel has recently been developed for reduction in size and simplification of the structure of cameras. The zoom lens barrel of this kind includes a stepped cam formed to have zoom driving cam areas and focus driving cam areas alternately arranged. This cam arrangement forms a lens driving mechanism which causes a photo-taking lens to perform stepwise zooming and to perform focusing at each zooming step.
However, the stepped zoom lens barrel has the following problem. Since the zoom mechanism and the focusing mechanism are arranged in one body, the above-stated arrangement for simply interlocking a flash device with the lens barrel would causes the flash device to be driven also in focusing. In the event of such driving, the distribution of light quantity and the guide number of the flash device would vary to cause differences in finished photographs.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a stepped zoom type camera simply arranged to be capable of giving always an optimum luminous intensity distribution angle of a flash device.
To attain the above object, in accordance with an aspect of the invention, there is provided a camera, which comprises a lens barrel having a cam part in which a plurality of magnification varying cam areas for varying magnification and a plurality of focusing cam areas for focusing are alternately formed in a continuous manner, a flash light emitting part arranged to be capable of varying a luminous intensity distribution angle, driving means for causing the lens barrel to move along an optical axis while rotating around the optical axis, the lens barrel having a lens thereof driven along the cam part to perform a magnification varying action or a focusing action, and control means for controlling the luminous intensity distribution angle of the flash light emitting part in association with the rotation of the lens barrel in such a way as to cause the luminous intensity distribution angle of the flash light emitting part to vary when the lens is driven to move along one of the plurality of magnification varying cam areas and to cause the luminous intensity distribution angle of the flash light emitting part not to vary when the lens is driven to move along one of the plurality of focusing cam areas.
In particular, in the camera, the flash light emitting part includes a light source and a Fresnel lens, and the control means causes a relative interval between the light source and the Fresnel lens to vary.
Further, in the camera, the control means has a rotary cam in which a cam part where an amount of lift varies in one of the plurality of magnification varying areas and a cam part where the amount of lift remains constant in one of the plurality of focusing cam areas are formed, and the flash light emitting part is arranged to vary the luminous intensity distribution angle thereof according to the amount of lift of the rotary cam.
Further, in the camera, the rotary cam is arranged to rotate in association with the rotation of the lens barrel.
Further, the camera further comprises a lever arranged to be driven to move by the cam part of the rotary cam, and the luminous intensity distribution angle of the flash light emitting part varies in association with the driven movement of the lever.
Further, in the camera, the flash light emitting part is in a state of being stowed within a body of the camera when the lens barrel is in a state of not being used.
Further, in the camera, the flash light emitting part is in a state of being popped up from the body of the camera when the lens barrel is in a state of being used.
In addition, in accordance with another aspect of the invention, there is provided a camera, which comprises a lens barrel having a cam part in which a plurality of magnification varying cam areas for varying magnification and a plurality of focusing cam areas for focusing are alternately formed in a continuous manner, a flash light emitting part arranged to be capable of varying a luminous intensity distribution angle, driving means for causing the lens barrel to move along an optical axis while rotating around the optical axis, the lens barrel having a lens thereof driven along the cam part to perform a magnification varying action or a focusing action, and a rotary cam member arranged to rotate in association with the rotation of the lens barrel, the rotary cam member having, formed therein, a cam part where an amount of cam lift varies correspondingly with one of the plurality of magnification varying cam areas and a cam part where the amount of cam lift remains constant correspondingly with one of the plurality of focusing cam areas, wherein the flash light emitting part is arranged to vary the
Adams Russell
Robin Blecker & Daley
Smith Arthur A
LandOfFree
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