Photography – Flash system responsive to focal length or distance – Illumination angle responds to focal length or distance
Reexamination Certificate
2001-03-30
2002-12-10
Perkey, W. B. (Department: 2851)
Photography
Flash system responsive to focal length or distance
Illumination angle responds to focal length or distance
C396S079000
Reexamination Certificate
active
06493510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a zoom flash device. More particularly, the present invention relates to a camera having a zoom flash device including a zoom optical system and a flash emitter, and in which emission of flash light in the flash emitter can be optimized in any zoom position from a wide-angle end to a telephoto end in the zoom optical system.
2. Description Related to the Prior Art
A zoom flash device is known, which has a zoom optical system, in which a zoom motor drives and zooms the zoom optical system, and in which an illuminating angular range of flash light is changed according to zooming. To change the illuminating angular range, angles of portions of a reflector are changed. Also, distances from a Fresnel lens to a flash discharge tube and the reflector are changed.
JP-A 4-235511 discloses the zoom optical system of a type in which one of plural lens groups is a focusing lens group. A zoom position and an object distance are considered to calculate and obtain an in-focus position. The focusing lens group is moved to the in-focus position for focusing. A focusing motor, which is additional to the zoom motor, is driven to move the focusing lens group to the in-focus position. To move the focusing lens group with precision, a rotary encode is combined with the focusing motor, detects a rotational angle of the focusing motor to control a stop of the focusing motor.
When the focusing lens group in the zoom optical system is moved to the in-focus position according to a certain object distance, there is a tendency in that a moving amount of the focusing lens group is higher in zooming to the wide-angle side and smaller in zooming to the telephoto side. According to the prior art, definition of a rotary encoder is predetermined so as to obtain sufficient precision at a wide-angle end.
If the zoom optical system has a high zoom ratio, this tendency becomes more conspicuous. A rotary encoder of a high precision is required for obtaining sufficient precision in focusing at the wide-angle end, and causes a high cost. Furthermore, a moving amount of the focusing lens group at a telephoto end is specifically high. There occurs a problem in taking long time in the focusing operation. So it is conceivable to move all the lens groups together for focusing at the wide-angle end by use of rotation of the zoom motor.
However, there occurs a problem in use of a zoom flash device in a camera in which focusing is effected at the wide-angle end by driving the zoom motor. As the illuminating angular range is changed according to rotation of the zoom motor, the illuminating angular range is changed also in the course of focusing at the wide-angle end. This lowers distribution in emitting flash light when the zoom optical system is set at the wide-angle end.
SUMMARY OF THE INVENTION
In view of the foregoing problems, an object of the present invention is to provide a camera having a zoom flash device including a zoom optical system and a flash emitter, and in which an illuminating angular range of flash light can be determined suitably so that emission of flash light in the flash emitter can be optimized in any zoom position from a wide-angle end to a telephoto end in the zoom optical system.
In order to achieve the above and other objects and advantages of this invention, a camera has a zoom optical system, which includes plural lens groups disposed on an optical axis, for being set at least between a wide-angle end and a telephoto end. A lens moving mechanism is movable in first and second moving regions continuous with each other, for moving the zoom optical system along the optical axis, the first moving region being adapted to zoom the zoom optical system. A flash emitter emits flash light to a photographic field within an illuminating angular range. An illuminating range changer has a transmission section and a non-transmission section, the transmission section operating when the lens moving mechanism is in the first moving region, for changing the illuminating angular range, the non-transmission section operating when the lens moving mechanism is in the second moving region, for keeping the illuminating angular range unchanged.
The second moving region is adapted to focus the zoom optical system.
When the lens moving mechanism is in the first moving region, the transmission section decreases the illuminating angular range according to movement of the zoom optical system to the telephoto end. When the lens moving mechanism is in the second moving region, the non-transmission section maximizes the illuminating angular range.
The transmission section moves the flash emitter in a direction along the optical axis.
The flash emitter includes a flash discharge tube for emitting the flash light. A Fresnel lens or flash emitting window is disposed in front of the flash discharge tube, for passing the flash light from the flash discharge tube. The illuminating range changer adjusts a distance of the flash discharge tube from the flash emitting window in a backward direction, the transmission section increases the distance for the flash emitting window to decrease the illuminating angular range, and the non-transmission section minimizes the distance.
The first moving region corresponds to a section between a predetermined zoom position and the telephoto end, and second moving region corresponds to a section between the wide-angle end and the predetermined zoom position. The predetermined zoom position is defined one zoom step shifted from the wide-angle end toward the telephoto end.
The lens moving mechanism includes a zoom motor. The illuminating range changer includes a transmission plate for moving in response to rotation of the zoom motor. A driving pin is formed to project from the transmission plate, for being in a first stroke when the lens moving mechanism is in the first moving region, and being in a second stroke when the lens moving mechanism is in the second moving region. A transmission lever moves the flash emitter by swinging. A cam groove is formed in the transmission lever, for receiving the driving pin, having the transmission section and the non-transmission section, the transmission section being pushed by the driving pin in the first stroke to swing, the non-transmission section keeping free the driving pin in the second stroke, to disconnect the transmission lever from the driving pin.
The transmission plate slides, and the first and second strokes are collinear with each other.
The transmission plate is a transmission rack. Furthermore, a transmission gear train includes input and output gears, the input gears being driven by the zoom motor, the output gear being meshed with the transmission rack.
The flash emitter further includes a flash case for containing the flash discharge tube and for being moved by the transmission lever.
Furthermore, there is a stationary barrel. The lens moving mechanism further includes at least one intermediate barrel, coupled helically with an inside of the stationary barrel, rotated relative to the stationary barrel by the zoom motor, for moving along the optical axis. A movable barrel is contained in the intermediate barrel, for supporting the zoom optical system. At least one cam mechanism moves the movable barrel along the optical axis in response to rotation of the intermediate barrel.
REFERENCES:
patent: 4914461 (1990-04-01), Hori
patent: 5819121 (1998-10-01), Tsuboi
patent: 4-235511 (1992-08-01), None
Fuji Photo Optical Co., Ltd.
Perkey W. B.
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