Single use camera with built-in electronic flash

Details Single use camera with built-in electronic flash Single use camera with built-in electronic flash

1998-10-29

2002-01-15

Gray, David M. (Department: 2851)

Photography

Disposable or recyclable camera

C396S176000, C396S179000

Reexamination Certificate

active

06339679

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a single use camera with built-in electronic flash.
In the conventional single use camera with built-in electronic flash, in the stroboscopic photographing, there is a problem in which a main object in a distance of 2-3 m is a little overly exposed into a rather white image, and, on the other hand, its background is a little under-exposed into a rather dark image, resulting in unbalance as a total image.
Further, recently, in the single use camera, due to its increasing competition in the market, requirements for the unit are to design it to be more compact, and to manufacture it to be more inexpensive. Specifically, in the single use camera with built-in electronic flash, the influence of the electronic flash on the reduction of size or cost is extremely great.
As a type of electronic flash switch actuator, there is an automatic-return type which is turned ON when only operated by the operator, and which is returned to an OFF-state when the operator does not touch it, and which also opens a main switch in the electronic flash circuit, and a state holding type such as a slide type, seesaw type, or standing-up type, which holds the ON-state even when the operator stops touching it, and which maintains a main switch in the electronic flash circuit to be closed.
When the electronic flash switch actuator is the type of state holding type, there is an advantage that no charging operation is required for each continuous stroboscopic photographing, however, when the operator forgets to turn OFF the electronic flash switch actuator, and an ON state continues, the electronic flash charging operation is continued, resulting in useless consumption, and therefore, there is a possibility that stroboscopic photographing comes to be impossible before the entire exposures of a film roll are exposed.
For example, as an example of the single use camera with built-in electronic flash now in the market, an alkaline dry battery of 1.5 volts is used as its power source. When resistance of a step-up circuit of the electronic flash circuit is 220 &OHgr;, the holding time of the dry battery voltage more than 1 v by which the electronic flash unit can be charged, is about 6 hours (refer to FIG.
14
). Accordingly, when a night is over while the operator forgets turning OFF the electronic flash switch actuator, there is a case where, on the next day, the battery is exhausted up and no stroboscopic photographing can be done.
Further, in an electronic flash circuit of the conventional electronic flash unit, two switches are required one of which is a main switch to charge the electronic flash unit when it is used, and the other of which is a light emission stop switch to turn OFF a neon tube and to stop the light emission of the electronic flash unit even when the main capacitor is charged. Thereby, it results in cost-up, and further, there is a case where an electronic flash unit failure caused by these switches occurs.
Herein, the conventional electronic flash unit will be detailed below. The conventional electronic flash circuit is shown in FIG.
2
.
In
FIG. 2
, BT is a battery consists of a SUM-3 type (or AA type) or SUM-4 type (or AAA type) dry battery, and when stroboscopic photographing is carried out, a main switch SW
1
and a light emission stop switch SW
2
are turned ON by operating an external operation member. Then, DC current is supplied from the battery BT to an oscillation transistor Q, oscillation transformer T
1
, and a resistor R
1
through the main switch SW
1
, and an oscillation operation is carried out so that low DC voltage is converted into AC high voltage.
The AC high voltage outputted from the oscillation transformer T
1
is rectified by a diode D, and charges the main capacitor C
1
. Further, a trigger capacitor C
2
is charged through a resistor R
2
. When the voltage of the trigger capacitor C
2
reaches a predetermined voltage value, the voltage is applied to a resistor R
3
and a neon tube Ne, and the neon tube Ne starts discharging, that is, it is turned ON.
As described above, after the neon tube Ne is turned ON, when a release button, not shown, is pressed, a shutter blade is opened, and when the blade is fully opened, a trigger switch TSW is turned ON. When the trigger switch TSW is turned ON, electric charges, which are charged in the trigger capacitor C
2
, are discharged onto a primary winding T
21
of a trigger coil T
2
, high voltage is generated in a secondary winding T
22
and the voltage is applied to a trigger electrode G of a discharge tube Xe. As the result, ionized xenon atoms in the discharge tube Xe collide with electrons sprung out from a cathode and are excited, and thereby, the discharge tube Xe is lit.
Further, while the main capacitor C
1
is charged and the neon tube Ne is lit, when the main switch SW
1
is turned OFF by operating the external operation member, the oscillating operation is stopped. Further, the light emission stop switch SW
2
is also simultaneously turned OFF, thereby, the neon tube Ne is turned OFF, and even when the release button is further pressed and the trigger switch TSW is turned ON, the trigger capacitor C
2
does not discharge, thereby, the discharge tube Xe does not emit light.
Next, as an alternative means for cost reduction, it is also considered that, as an indicator lamp, an expensive neon tube is not used, but an inexpensive light emitting diode is used, and the description relating to this is disclosed in Japanese Patent Publication Open to Public Inspection No. 115796/1996. However, when the neon tube is not used but the light emitting diode is used, there is a problem that the trigger voltage outputted from the trigger transformer becomes too high. Further, when the light emitting diode is used as the indicator lamp, an amount of light emission or lighting timing can be adjusted using characteristics of the light emitting diode, however, in the structure stated above, in which the tertiary winding of the oscillating transformer is used also for a lighting circuit of the light emitting diode, there are disadvantages that the number of windings of the tertiary winding is set for the control of the oscillating transistor, therefore, when the number of windings of the tertiary winding is increased or decreased for, for example, the light amount adjustment of the light emitting diode, the discharging voltage is lowered, thereby, the charging characteristics are also changed like that, for example, a long period of time is necessary for charging.
In this connection, a detail of the conventional electronic flash circuit in which the light emitting diode is used as the indicator lamp, is shown in FIG.
25
. An electronic flash circuit
301
is largely divided into a step-up circuit
302
to step up the power source such as a dry battery BT, and a flash light emitting circuit
303
to make the electronic flash light emitting tube Xe emit light. In the step-up circuit
302
, an oscillating transformer TR
1
and oscillating transistor Q, and further, a light emitting diode LED as an indicator lamp are provided, and in the flash light emitting circuit
303
, an electronic flash light emitting tube Xe, a main capacitor MC, and a trigger switch TSW are provided.
The oscillating transformer TR
1
in the step-up circuit
302
has a primary winding W
1
, a secondary winding W
2
, and a tertiary winding W
3
as a feed back winding. The AC high voltage is generated in the secondary winding corresponding to a turns ratio of primary winding to secondary winding, and the tertiary winding W
3
controls to stabilize the base potential voltage of the oscillating transistor Q, and the light emitting diode LED is connected to both ends of the tertiary winding W
3
of the oscillating transformer TR
1
, and thus, a light emitting diode lighting circuit
304
(hereinafter, referred to as LED lighting circuit) is structured.
The high voltage generated by the oscillating transformer TR
1
by turning ON the main switch MSW, charges the main capacitor MC in the flash light emitting cir

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