Photography – With object illumination for exposure – Having artificial illumination termination control
Reexamination Certificate
1999-04-29
2001-01-16
Adams, Russell (Department: 2851)
Photography
With object illumination for exposure
Having artificial illumination termination control
C396S198000
Reexamination Certificate
active
06175695
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to flashlights, and more particularly to a manually operable flashlight unit having a foot part fitting a finder shoe on a camera, standard contacts for chassis ground and flash release being arranged in the foot part.
2. Description of the Related Art
In flashlight units of this type, the flash is released by the camera via the so-called X contact, and the flash is switched off by a photodiode incorporated in the flashlight unit together with an evaluation electronic system as soon as a sufficient light intensity is reached. The adaptation to different lens diaphragms (apertures) and film speeds is performed via a change-over switch fitted on the flashlight unit.
The internal automatic switch-off device of the flashlight unit can also be disconnected so that the flash always shines with its full intensity. In the case of this so-called manual mode, the diaphragm must then be set manually at the lens in accordance with the desired range and film speed, in order to achieve the suitable brightening up from the flash.
Flashlight units integrated in compact cameras generally operate only in manual mode. The automatically setting diaphragm is calculated from the fixed guide number of the integrated flash and the measured range. The flash intensity and the flash duration are not controlled.
It is also known, for example from DE 32 21 856 A1, to arrange further contacts in the foot part of the flashlight unit and in the finder shoe of the camera in addition to the X contact. The available space is very restricted, with the result that at most two further contacts are provided in general. The position and importance of these contacts are usually specific to the company, while the shape of the foot part and finder shoe as well as the position of the contacts for the chassis ground in the respective outer molded part, and of the X contact in the central position, are fixed by an international standard. It is possible, for example, for the mounted flashlight unit to be switched on and a flash-ready signal to be sent to the camera via the further contacts.
When the flashlight unit is switched on, the flash capacitor integrated in the unit is charged in a certain time. When the necessary charge is reached, the flashlight unit transmits a signal to the camera via the flash-ready contact. Normally, the signal comprises a voltage level of a few volts with respect to ground, which, for example, is used for a display in the camera or triggers the shutter release. The designation AX contact has become established for this contact.
The flash power of separate flashlight units which can be mounted on the camera is substantially higher than that of a flashlight unit integrated in the camera, since the power supply via batteries and the installation space for charging capacitors in the camera are restricted. It is therefore desired also to be able to mount an external flashlight unit on cameras with an integrated flashlight unit. However, the problem arises in this case, on the one hand, of being able to disconnect the integrated flashlight unit as automatically as possible and, on the other hand, of switching the external flashlight unit into the same operating mode as the integrated flashlight unit. Given the multiplicity of already existing contact arrangements and dimensions, standardized overall, of the finder shoe, it is not possible in a technically sensible way to fit further contacts or switches. Moreover, additional contacts in the foot part of the flashlight unit would restrict its usefulness on different cameras.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.
SUMMARY OF THE INVENTION
The present invention is directed to creating a flashlight unit which can be mounted on different camera models and by means of which it is also possible to realize particular requirements in the case of individual camera models.
According to an embodiment of the invention, in the case of a flashlight unit of the type mentioned in the beginning, in addition to the two standard contacts, a single further contact is provided for bidirectional information exchange between circuit arrangements in the flashlight unit and in the camera. This contact is advantageously an AX contact. In this case, inside the flashlight unit the further contact is assigned a circuit arrangement by means of which, firstly, a flash-ready signal to be transmitted to the camera is generated, and which generates a flash-mode control signal from a signal triggered by the camera as a function of said flash-ready signal. The flash-ready signal can comprise a specific signal voltage level which, in the event of shutter release by the circuit arrangement in the camera, can be varied to a lower signal voltage level which can be detected by the circuit arrangement in the flashlight unit. The flash-mode control signal can effect the manual mode setting through which the camera exerts control.
Using only one further contact, whose function is primarily controlled by the flashlight unit, the flashlight unit can be used on all cameras which contain only the standard contacts in their finder shoe. The further contact then has no counter pole. The camera can therefore not react to the flash-ready signal provided, with the result that in the event of flash release via the X contact, the operating mode respectively set on the flashlight unit comes into effect. The flash readiness must be observed via a display on the flashlight unit.
In the case of cameras having an AX contact which makes contact with the further contact in the foot part of the flashlight unit, the flash-ready signal can, furthermore, be used to display and/or to trigger the shutter release. To the extent that no additional change signal is generated by the camera, the flashlight unit can likewise be used in the respectively set operating mode via the shutter release and the X contact.
In addition, however, it is also possible, for example, to equip compact cameras with a finder shoe and suitable AX contact, and to provide inside the camera a circuit arrangement which, as a function of the flash-ready signal, on the one hand switches off an integrated flashlight unit and, on the other hand, undertakes to change the signal voltage level at the AX contact so that the flashlight unit is switched by its circuit arrangement into an operating mode which is matched to the integrated flashlight unit.
In the case of cameras with further contacts, for example for automatically switching on the flashlight unit, the flashlight unit according to the invention can likewise be used, but only after being switched on manually.
Briefly, according to one aspect of the present invention, there is provided a manually operable flashlight unit having a foot part fitting a finder shoe on a camera. Standard contacts for chassis ground and for flash release are arranged in the foot part. A single further contact is provided in the foot part for bidirectional information exchange between a circuit arrangement contained in the flashlight unit and a circuit arrangement arranged in the camera.
Briefly, according to another aspect of the present invention, there is provided a flashlight unit for use with a camera. The flashlight unit includes a bidirectional information exchange contact and a flashlight circuit. The flashlight circuit is electrically coupled to the bidirectional information exchange contact. The bidirectional information exchange contact allows bidirectional communication between the flashlight circuit and a camera circuit on the camera. The flashlight circuit generates communication signals for the camera circuit and is adapted to receive communication signals from the camera circuit via the bidirectional information exchange contact.
Briefly, according to another aspect of the present invention, there is provided a camera system. The camera system includes a camera and a flashlight unit. The camera includes a camera-side bidirection
Bletz Walter
Schaefer Klaus Dieter
Adams Russell
Foley & Lardner
Leica Camera AG
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