GB2140936A - Electronic flash with remote sensor - Google Patents

Abstract

A flash unit, capable of operating as a remote or slave flash, has a dome 14, which surrounds the flash bulb 20 and is in light conducting relationship with a photodetector 24. On receipt of a predetermined quantity of light the detector triggers the bulb to flash. By using the dome light from a large directional range causes the bulb to flash. In an alternative embodiment the dome is connected to a light pipe which conducts light to the detector. <IMAGE>

Description

SPECIFICATION Electronic flash device with remote sensor The present invention relates to electronic flash devices, and more particularly to a remote or slave-type electronic flash.

A slave flash unit is a device which is used in conjunction with a master flash unit to provide fill-in or background lighting in photography. The slave flash units are located at different points and provide light as required forthe photograph. The slave flash is related to the main flash so that requisite lighting ratios are achieved for optimum lighting effect such as key, fill, highlight and background lighting. A master flash unit is a unit which is directly operated by a camera and, on shutter activation, the master unit fires its flash and conventionally the slave unit operates simultaneously. The slave units are, conventionally, either connected to the master unit by wires or have electronic light sensor means which respond to light from the master flash such that their operation is triggered upon firing of the master flash.

In the operation of an electronic flash unit, the activation of the camera shutter triggers the flash, causing light to be generated. If the flash is of the automatic type, extinction of the flash can occur after a predetermined amount of light is reflected from the scene being photographed and detected by a sensor assocated with the flash.

Various arrangements for master-slave flash units are known in the art. For example, U.S. Patent No.

4,287,453 and No. 3,917,944 disclose slave flash devices. Other slave flash devices or circuits useful therewith are disclosed in U.S. Patent No. 2,776,364, No.3,487,221, No.3,601,652, No.3,288,044, No.

3,196,275, No. 2,486,010, No.3,312,086, No.

3,636,406 and No. 3,944,877.

In accordance with the present invention, a new form of sensing system is provided for a remote or slave type flash incorporating a bare bulb head and wherein the slave light sensor is disposed in an optically conductive relationship with the dome of the head.

Accordingly, a principal object of this invention is to provide an improved form of optical sensor for an electronic flash device.

Another object of this invention is to provide an improved form of slave or remote flash device.

These and other objects and features of the present invention will become better understood through a consideration of the following description taken in conjunction with the accompanying drawings in which: Figure 1 shows an electronic flash device with a bare bulb head which may use the concepts of the present invention; and Figure 2 is a perspective view of a bare bulb head module incorporating the present invention.

Turning now to the drawings, Figure 1 is an elevational view of an essentially conventional form of electronic flash unit 10 having a body 11 and bare bulb head module 12. The body 11 includes, as is known, appropriate electronic circuitry for interfacing with an associated camera (not shown) for causing an electronic flash tube in the module 12 to fire when the camera sync contacts are closed, and to cause the flash of light to be terminated when sufficient light has been received by a light sensor 13 of the body 11. The module 12 includes a flash tube (note flash tube 20 of Figure 2) which is covered by a clear or translucent dome 14. This type module provides natural lighting effects.The head 12 also includes appropriate electrical connections to allow the head 12 to be plugged and unplugged with respect to the body 11 and for transferring the appropriate electrical signals for control of the flash.

The flash unit shown in Figure 1 can be similar to the Model 4600 sold by Vivitar Corporation.

Typically, the light sensor 13 of the flash unit 10 responds to the light reflected from the subject being photographed, and is used to terminate the flash of light from the flash tube of the flash unit 10.

However, this light sensor or another similar light sensor may be used in electronic flash units to respond to the flash from another form of flash unit and to, in turn, cause the flash tube of the unit 10 to trigger and emit light. In this case, the unit 10 functions as a remote or slave type flash device.

In accordance with the present invention, a light sensor is provided optically coupled to the dome 14 of the head 12. Turning to Figure 2, the bare bulb head 12 has a dome 14 which preferably is a clear plastic protective dome. The flash tube 20 is shown within the dome 14. A light sensor 24 is mounted in the upper part of the body 26 of the head 12 and preferably in intimate physical contact with a bottom edge 28 of the dome 14. Placing the sensor 24 in contact with the dome 14 converts a relatively directional sensor to an omni-directional sensor. The sensor 24 is appropriately connected to the trigger circuit of the flash unit, and when sufficient light is received by the sensor 24, the flash tube 20 is triggered to emit light.It is believed that by placing the light sensor 24 in optical contact with the dome 14 light passing through the dome will be transmitted to the light sensor 24 so that the sensor can be activated not only by light directly impinging on the sensor 24, but also by light impinging on the dome 14 and conducted to the sensor 24 by the material of the dome. This is believed to increase the possibility that light, not directed at the sensor but hitting the dome, will reach the sensor to thereby increase the amount of light received by the sensor and thus increase the operating range of the sensor. Accordingly it is believed that the dome 14 and sensor 24 arrangement provides a relatively simple and efficient way of increasing the light gathering or light receiving capability of the sensor 24.It should be noted that as an alternative to placing the edge 28 of the dome 14 in contact with the surface of the light sensor 24 a light pipe can be used to convey light from the dome to the sensor.

The dome 14 may be formed of the usual material from which the domes of bare bulb heads are made, such as acetate. The dome 14 may be affixed to the body 26 of the head 12 in a conventional manner.

The sensor 24 may be a photoresistor or the like. A suitable electronic circuit, indicated by dashed lines, such as of the nature described in U.S. Patent No. 3,917,944, No.3,749,921, No.4,287,453, No.

4,201,934 or the like may be used with the sensor 24 for triggering the flash tube 20.

While a preferred embodiment of the present invention has been illustrated and described, modifications and variations thereof will be apparent to those skilled in the art given the teachings herein, and it is intended that all modifications and variations be encompassed within the scope of the appended claims.

Claims (5)

1. An electronic slave flash device comprising a flash head including an electronic flash tube, a light sensor disposed in said head, and a dome coupled with said head, said dome being formed of a material capable of conducting light from a light flash and being so mounted with respect to said light sensor as to conduct light received by the dome to the light sensor.

2. An electronic slave flash device as claimed in Claim 1 including electronic circuit means, connected between the light sensor and the flash tube, for causing the flash tube to be triggered and emit light when a predetermined amount of light has been received by the light sensor.

3. An electronic slave flash device as claimed in Claim 2 wherein said dome is formed of clear plastics material having a lower edge attached to said head, the lower edge of said dome being in contact with said light sensor.

4. An electronic slave flash device as claimed in Claim 1 including a body for housing electronic circuit means of the flash device, said flash head being removably connected with said body, said dome being so mounted with respect to said light sensor as to conduct light received by the dome through an edge thereof to the light sensor, and electronic circuit means, connected between the light sensor, electronic circuit means and the flash tube, for causing the flash tube to be triggered and emit light when a predetermined amount of light has been received by the light sensor.

5. An electronic flash device substantialy as herein described with reference to both Figures of the accompanying drawings.