Flash photography system

In a flash photography system which controls the amount of flash based on an aperture value of a lens set by detecting reflected light from an object which is preliminarily illuminated prior to main illumination, the angle of illumination coverage of a main light issuing portion is variable, and the amount of light from the preliminary illumination is determined corresponding to that varied angle. The aperture value of the lens is properly set by the preliminary illumination corresponding to that varied angle.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to flash photography systems, and more particularly 
to flash photography systems in which an aperture value is determined by 
preliminary illumination and the amount of main illumination is controlled 
in accordance with that aperture value. 
2. Description of the Prior Art 
The electronic flash device in which the aperture of the photographic lens 
is determined in correspondence to the received amount of the reflection 
of the preliminary illumination, and the main illumination is controlled 
at a corresponding critical level to that aperture value, has already been 
proposed in Laid-Open Patent Application No. SHO 58-102221 in Japan. Also, 
in this kind of electronic flash devices, there have been previous 
proposals for using annular illumination coverage varying means in the 
main flash issuing portion alone, or in combination with another angular 
illumination coverage varying means in the preliminary light issuing 
portion. In the latter case, the angle of illumination coverage by the 
preliminary light issuing portion is made to vary in response to operation 
of varying the angle of illumination coverage of the main flash light 
issuing portion so that the preset aperture value by the preliminary 
illumination always coincides with the electronic flash photographable 
range of the main illumination. Yet, the aforesaid main illumination 
coverage angle varying means and the aforesaid preliminary illumination 
coverage angle varying means of the conventional device each are 
constructed by an optical member such as a lens, or diffusion plate 
provided in front of the light issuing portion, and the optical member of 
the aforesaid preliminary light issuing portion is arranged to move in 
response to the illumination coverage angle varying means when the 
aforesaid optical member of the main light issuing portion moves. 
Meanwhile, the size of the main light issuing portion itself in this kind 
of electronic flash device is very large compared with the preliminary 
light issuing portion. So, the aforesaid movements of the main and 
preliminary light issuing portions are largely different from each other. 
Therefore, a problem arose that there was need to use a very complicated 
linking mechanism between the illumination coverage angle varying means of 
the main light issuing portion and that of the preliminary light issuing 
portion. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an electronic flash device 
which has overcome the above-described problem and which is, despite the 
illumination coverage angle of the main light issuing portion being varied 
by the illumination coverage angle varying means, able to determine the 
amount of light for the preliminary illumination corresponding to that 
varied angle to properly set an aperture value of a lens, while still 
permitting the structure of construction to be simplified. 
Under such an object, the invention of this application is to provide for 
the flash photography system having main light issuing means for producing 
main illumination for exposure and preliminary light issuing means for 
producing preliminary illumination prior to the main illumination to 
obtain information for making the exposure with the main illumination, 
with means for varying the angle of illumination coverage with light from 
the main light issuing means and control means for controlling the amount 
of emitted light from the preliminary light issuing means to vary the 
object light amount in accordance with the angle of illumination coverage 
of said illumination coverage angle varying means. 
Other objects of the invention will become apparent from the following 
description of preferred embodiments thereof by reference to the 
accompanying drawings.

DETAILED DESCRIPTIN OF THE PREFERRED EMBODIMENTS 
In FIG. 1(a) there is shown the electronic flash device of the invention 
usable with a single lens reflex camera, comprising a battery 8, a power 
switch 9, a DC-DC converter 10 for boosting D.C. voltage, diodes 11 and 
12, preliminary illumination energy storage capacitors 13W, 13N and 13T 
selectively usable for firing a preliminary flash discharge tube 14, a 
selector switch SW1 arranged to move in response to movement of an 
illumination coverage angle varying member of the main light issuing 
portion, and a trigger tigger circuit 16. This circuit comprises a 
resistor 17, a transformer 18, a capacitor 19, a thryistor 20 and a 
resistor 21. Another trigger circuit 22 is included for triggering a flash 
discharge tube 23 for main illumination, and comprises a resistor 24, a 
capacitor 25, a transformer 26, a thyristor 27, and a resistor 28. A diode 
29 is connected as reversely biased in series with the discharge tube 23 
for the main illumination and in parallel with an inductor 30. 31 and 32 
are charging resistors for a commutation capacitor 33; 34 is a capacitor 
connected through a resistor 35 to the gate of a main thyristor 36; 37 is 
an auxiliary thyristor; 38 and 39 are resistors; 40 is a light amount 
control circuit; 41 is a main capacitor for firing the discharge tube 23 
for the main illumination with which a flash exposure is made; 42 is a 
switch arranged to turn on when a shutter release buttn (not shown) is 
pushed down to a first stroke; 43 is a synchro switch which turns on in 
synchronism with the actuation of a shutter release as is known in the art 
T1 is a timer circuit for prelimimary illumination; T2 is a timer circuit 
for main illumination; G1 is a gate circuit receptive of a signal of high 
level from the timer circuit T1 or T2 for turning off transistor 44; 45 is 
a photosensitive element arranged to receive the reflected light from an 
object to be photographed; 46 is an integration capacitor to be charged 
with photo-current from the photosensitive element 45; 47-51 are resistors 
of a voltage divider; 52-54 are comparators; M is a memory circuit; 55-57 
are transistors; 58-60 are integration capacitors; G2 is a gate circuit; 
61 is a transistor whose opening-and-closing operation is controlled by 
the output of the gate circuit G2; 62 and 63 are resistors of a voltage 
divider; 64 is a comparator for turning on the auxiliary thyristor 37; OP 
is an aperture control signal forming circuit; 65 is an outlet at which 
the aperture control signal is produced to the camera side. 
FIGS. 2(a) and 2(b) illustrate the outer appearance of the flash device. 
Provided in a body 200 of the flash device are the aforesaid main flash 
discharge tube 23 for flash photography fixedly secured to a reflector 
201, the aforesaid discharge tube 14 for preliminary illumination fixedly 
secured to a reflector 202, and the aforesaid photo-sensitive element 45 
for measuring the reflected light from the object to be photographed 
through a collection lens PTa. A protection panel 203 of acrylic material 
is positioned in front of the main light issuing portion including the 
main discharge tube 23 and is supported between portions 200a and 200b of 
a casing of the body 200. A filter 204 for transmitting only the infrared 
light is positioned in front of the preliminary light issuing portion 
including the flash discharge tube 14 for preliminary illumination so that 
the model to be photographed does not feel unpleasantness by the flash 
light issued from the discharge tube 14 for prelimimary illumination. A 
Fresnel lens 205 for the main light issuing portion is supported between 
portions 207a and 207b of a casing of an adapter 207. 206 is a Fresnel 
lens for preliminary illumination. 207a and 207b are portions of the 
casing of the adapter 207 which are constructed in unified form. And, the 
portion 207a of the casing of the adapter 207 slidingly moves on the 
portion 200a of the casing of the flash device body 200 while the other 
portion 207b of the casing of the adapter 207 slidingly moves in a groove 
formed in the portion 200b of the casing of the body 200, so that the 
angle of illumination coverage of the main light issuing portion becomes 
possible to vary. 
Also in the lower surface of the portion 200b of the casing of the body 200 
there are push buttons 208 arranged to be selectively operated depending 
on the value of the illumination coverage angle of the main light issuing 
portion for the wide angle, standard or telephoto shooting, in other 
words, the axial position of the adapter 207. By the pushed state of said 
push buttons, it can be known that the main illumination is adapted to 
either wide angle, or standard, or telephoto shooting. Responsive to this 
pushed state, the switch SW1 selects one of the capacitors 3W, 13N and 
13T. 
Next explained is the operation of the flash device of construction 
described above. In this embodiment, the angle of illumination coverage 
can be varied in three steps suited to the wide angle, standard and 
telephoto photo objectives. When the angle of illumination coverage of the 
main light issuing portion is selectively set for the wide angle, normal 
or telephoto shooting, the illumination coverage angle varying member 207 
of the main light issuing portion of FIG. 2(a) moves the switch SW1 to 
select the corresponding one of the capacitors 13W, 13N and 13T for 
preliminary illumination to the preset value of the illumination coverage 
angle. 
Also, in general, the narrower the angle of illumination coverage of the 
main light issuing portion, the larger the flash light guide number. So 
the values of capacitance of the capacitors 13W, 13N and 13T are 
previously determined to be 13W&lt;I3N&lt;13T. 
At first assuming that the angle of illumination coverage of the main light 
issuing portion is set for the normal objective, then the switch SW1 
selects the capacitor 13N for preliminary illumination. When the power 
switch 9 is turned on, the DC-DC converter 10 charges the capacitor 13N 
for preliminary illumination to a voltage high enough to fire the 
discharge tube 14 for preliminary illumination. Then when the shutter 
release button (not shown) is pushed down, the switch 42 is turned on, 
thereby each of the terminals t2 and t3 of the timer circuit T1 is changed 
to and maintained at high level for a prescribed time. Such change of the 
terminal t3 to high level causes the known trigger circuit 16 to operate. 
Then, the charge on the capacitor 13N is discharged through the flash 
discharge tube 14 for preliminary illumination. Thus, the discharge tube 
14 starts to fire. Meanwhile, when the signal of high level from the 
terminal t2 of the timer circuit T1 enters the terminal t1 of the gate 
circuit G1, the terminal t3 of the gate circuit G1 becomes low level, 
turning off the transistor 44, thereby the integration capacitor 46 is 
rendered chargeable. The photo-sensitive element 45 converts the incident 
light from the object (not shown) to current with which the integration 
capacitor 46 is charged. The voltage stored on the integration capacitor 
46 is proportional to the integrated amount of incident light from the 
object. The potentials at the junction points, a to c, of the voltage 
dividing resistors 47 to 51 are previously determined in correspondence 
with near, middle and far object distances, respectively. For example, for 
the far object distance, the integration capacitor 46 is charged to a 
higher voltage than the potential at the point c at a time when the firing 
of the preliminary light source terminates, but this voltage is lower than 
the potential at the point, b. Therefore, only the comparator 54 produces 
an output signal of high level. To the middle distance, the comparators 53 
and 54 produces output signals of high level. For the near distance, all 
the comparators 52 to 54 produce output signals of high level. After a 
prescribed time from the pushing down of the shutter release button, an 
input at the terminal t7 of the memory circuit M from the terminal t2 of 
the timer circuit T1 for preliminary illumination changes from high to low 
level, causing the memory circuit M to memorize the input levels at the 
terminals t1 to t3 thereof occurring at that time. Based on the memorized 
input levels, one of the transistors 55 to 57 is turned on. For example, 
if the outputs of the comparators 52 to 54 are all high level, the 
transistor 55 is caused to turn on, thereby the integration capacitor 58 
for the near object distance is selected. At the same time, responsive to 
turning on of either one of the transistors 55 to 57, the aperture control 
signal forming circuit OP produces an aperture control signal at the 
output terminal 65, from which it is applied to a diaphragm control 
circuit (not shown) within the camera body (not shown). At a prescribed 
time, therefore, the size of aperture opening of the diaphragm in the lens 
is caused to change depending on the object distance obtained by the 
preliminary illumination. 
Then when the shutter release button is further pushed down, the synchro 
contact 43 is turned on, thereby the terminals t2 and t3 of the timer 
circuit T2 for main illumination are changed to and maintained at high 
level for a prescribed time. Such change of the terminal t3 to high level 
causes the known trigger circuit 22 to operate. Then, the charge on the 
main capacitor 41 is discharged through the flash tube 23. So the 
discharge tube 23 starts to emit light. Meanwhile, when the signal of high 
level from the terminal t2 of the timer circuit T2 is applied to the 
terminal t1 of the gate circuit G2, the terminal t3 of the gate circuit G2 
becomes low level, turning off the transistor 61. Thereby charging of the 
one of the integration capacitors 58 to 60 which has been selected by the 
memory circuit M becomes possible. The reflection of the flash light of 
the flash discharge tube 23 from the object is received by the 
photo-sensitive element 45. The output of the photo-sensitive element 45 
in the form of current is stored on the one of the integration capacitors 
58 to 60 which has been selected by the memory circuit M. When the voltage 
stored on the selected one of the integration capacitors 58 to 60 becomes 
higher than the voltage at the junction point of the resistors 62 and 63, 
the comparator 64 produces an output signal of high level which is applied 
to the auxiliary thyristor 37, thereby the auxiliary thyristor 37 is 
turned on to reversely bias the main thyristor 36 with the charge stored 
on the commutation capacitor 33. The thyristor 36 is then turned off, thus 
terminating the firing of the flash discharge tube 23 for main 
illumination. 
It should be noted that though the application of the signal of high level 
from the terminal t2 of the timer circuit T2 for main illumination to the 
gate circuit G1 causes the transistor 44 to turn off and the integration 
capacitor 46 to be charged with current flowing from the photo-sensitive 
element 45, the loss of the current due to the charging of the integration 
capacitor 46 can be neglected because the capacitance of the integration 
capacitor 46 is far smaller than that of any one of the integration 
capacitors 58 to 60. 
Alternatively, assuming that the wide angle of illumination coverage is 
selected, then the capacitor 13W for preliminary illumination is selected 
by the switch SW1. The corresponding electrical energy stored on the 
capacitor 13W to the wide angle of illumination coverage is emitted as 
flash light from the discharge tube 14 for preliminary illumination, so 
that the distance to the object is detected in a similar manner to that 
described above. In another case when the telephoto angle of illumination 
coverage is selected, the capacitor 13T is selected by the switch SW1. The 
subsequent procedure is similar to that described in connection with the 
standard angle of illumination coverage. Therefore, its explanation is no 
more given here. In this embodiment, all the consituent elements are 
provided in the flash device casing. But, as shown in FIG. 1(b), they may 
be otherwise divided into two parts at line A--A', of which the lower part 
is provided within the camera housing. 
Also, though, in the above-described embodiment, a plurality of capacitors 
for preliminary illumination are selectively used, a modification may be 
made such that only one capacitor is provided for preliminary 
illumination, and the voltage to be applied to this one capacitor is made 
to vary with variation of the angle of illumination coverage of the main 
light issuing portion to effect an equivalent result to the above. Another 
example of modification is that while only one capacitor is used, and the 
voltage is maintained constant, a plurality of filters of different 
density are provided in front of the preliminary light issuing portion so 
that a proper one of the filters is selected depending on the angle of 
illumination coverage of the main light issuing portion. Conclusively 
speaking, any means can solve the object of the invention provided that 
the means can vary the amount of light to the object by the preliminary 
firing. 
As will be understood from the foregoing description, in the present 
invention, the light amount to the object to be photographed is made to 
vary in response to the illumination coverage angle varying operation of 
the main light issuing portion so that the preset aperture value by the 
preliminary illumination and the electronic photographable range of the 
main illumination can coincide with each other. So, when in the farther 
distance, a small aperture value can be set in, and when in the close 
distance, a large aperture value can be set in. Because all what to do is 
only to vary the light emitting energy electrically, there is no need to 
provide a complicated mechanism between the main light issuing portion and 
the preliminary light issuing portion, giving an advantage of simplifying 
the structure of construction.