Strobe device

A strobe device including a preparatory light radiator for generating a fixed amount of preparatory light a plurality of times to set an amount of actual light to be generated when radiating supplementary light onto a subject during photographing; an image pickup element for receiving a fixed amount of preparatory light, generated a plurality of times by the preparatory light radiator, and photoelectrically converting light reflected from the subject; an amplifier for amplifying the photoelectrically converted signal during the plurality of times of generating preparatory light, by an amplification factor which differs for each generation of preparatory light; a detector for detecting whether the average level of signals being output from the amplifier, for each generation of preparatory light, is within a predetermined range; and a calculator for calculating an amount of actual light to be generated based on signals output from the amplifier when the detector has determined that the average level of signals output from the amplifier is within the predetermined range.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a strobe device, and more particularly to 
a strobe device which radiates supplementary light onto a subject when 
photographing and generates preparatory light in order to set an amount of 
actual light to be generated. 
2. Related Art Statement 
Generally, when natural light alone is insufficient to provide the amount 
of light needed for photographing with an image pickup device such as a 
camera, a strobe device is for instance used to provide supplementary 
light. In this type of strobe device, the actual amount of light to be 
generated during exposure is set after first generating preparatory light, 
thereby ensuring that an appropriate amount of light is generated when 
photographing. When controlling the amount of generated light in this way, 
for instance, a controller such as disclosed in Japanese Unexamined Patent 
Publication No. 3-126383, which comprises a special-purpose photoreceptor 
for controlling the amount of light generated, is provided within the 
strobe device. 
Furthermore, Japanese Unexamined Patent Publication No. 59-119337 discloses 
an electronic camera system wherein no special-purpose photoreceptor or 
controller are provided, the amount of light generated being set based on 
an integrated output. 
However, according to the method of preparatory light generation disclosed 
in the abovementioned Japanese Unexamined Patent Publication No. 59-119337 
and such like, the amount of light to be actually generated is determined 
based on information obtained only by a single generation of preparatory 
light. Consequently, not only is there a disadvantage that a sufficient 
amount of light cannot be obtained when radiating onto a subject at long 
range, but also there is a disadvantage that a subject at close range is 
exposed to too much light. Thus it has been difficult to obtain an 
appropriate amount of light. 
OBJECTS AND SUMMARY OF THE INVENTION 
A first object of the present invention is to provide a strobe device for 
generating preparatory light capable of obtaining an optimum amount of 
light for actual light generation. 
A second object of the present invention is to provide a strobe device 
capable of obtaining image data which has been amplified to an optimum 
level for actual light generation. 
A third object of the present invention is to provide a strobe device 
capable of generating optimum preparatory light in accordance with a 
close-range subject, thereby obtaining an even more optimum amount of 
actual light generated. 
A fourth object of the present invention is to provide a strobe device 
capable of obtaining an optimum amount of light in actual light generation 
without providing an amplifier. 
Briefly, the strobe device of the present invention comprises: 
preparatory light radiating means for generating a fixed amount of 
preparatory light a plurality of times in order to set an amount of actual 
light to be generated when radiating supplementary light onto a subject 
during photographing; 
an image pickup element for receiving a fixed amount of preparatory light, 
generated a plurality of times by the preparatory light radiating means, 
and photoelectrically converting light reflected from a subject; 
amplifying means for amplifying a signal output from the image pickup 
element, which has been photoelectrically converted during the plurality 
of times of generating preparatory light, by an amplification factor which 
differs for each generation of preparatory light; 
detecting means for detecting whether the average level of signals obtained 
for each generation of preparatory light, the signals being output from 
the amplifying means, is within a predetermined range; and 
calculating means for calculating an amount of actual light to be generated 
based on signals output from the amplifying means when the detecting means 
has determined that the average level of signals output from the 
amplifying means is within the predetermined ranges. 
These objects and advantages of the present invention will become further 
apparent from the following detailed explanation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a block diagram showing the configuration of the strobe device 
according to a first embodiment of the present invention. 
The strobe device of the present embodiment principally comprises a 
photographing lens 1, which light from a subject is input to, a shutter 2 
which also functions as an aperture and is provided behind the 
photographing lens 1, a fixed image pickup element 3 such as a CCD for 
picking up an image of the subject whose light is input to the 
photographing lens 1, an amplifier 4 for amplifying an image signal picked 
up by the image pickup element 3, a signal processor (i.e. signal 
controller) 5 for sampling and holding an image signal amplified by the 
amplifier 4, an A/D circuit 6 for converting a signal from the signal 
processor from analog to digital, a memory 7 for storing a signal output 
from the A/D circuit 6, a CPU 8 for calculating the amount of light to be 
generated in a strobe light-generating tube 13, based on a signal output 
from the A/D circuit 6 or from the memory 7, and drive-controlling the 
parts that make up the strobe device, a timing generator 9 for generating 
a timing signal in order to drive the CCD3, a shutter controller 10 for 
controlling the shutter 2 in compliance with the CPU 8, a strobe 
light-generating tube 13 comprising for instance an Xc tube, a light 
generation amount controller 11 for controlling the amount of light 
generated by the strobe light-generating tube 13 in compliance with the 
CPU 8, a trigger electrode 12 for the strobe light-generating tube 13, a 
strobe light-generation mode switch (SW1) 14 which is connected to the CPU 
8, and a release switch (photography operation start switch SW2) 15 which 
is connected to the CPU 8. 
The amplifier 4 amplifies a signal output from the CCD 3 by a predetermined 
amplification factor based on a control signal from the CPU 8. 
Furthermore, the signal processor 5 processes the image signal amplified by 
the amplifier 4 by performing predetermined signal processing such as 
gamma correction or color correction. 
Furthermore, when the strobe light generation mode switch SW1 (14) switches 
ON, the CPU 8 generates strobe light; and, when the release switch SW2 
(15) switches ON, photographing commences under the control of the CPU 8. 
The operations of calculating the amount of actual light to be generated 
using preparatory light generation and photographing according to the 
strobe device of the first embodiment, having the configuration described 
above, will next be explained referring to the flowchart shown in FIG. 2. 
The strobe device of the present embodiment is characterized in that it is 
determined whether or not the amplification factor of the amplifier 4 is 
appropriate each time preparatory light is generated. 
As shown in FIG. 2, when the release switch 15 turns ON (Step S1), firstly, 
image data using only natural light is input and the CPU 8 determines the 
average value V0 of this natural light image data (Step S2). At this 
point, the amplification factor of the amplifier 4 for the image data 
being input is directly measured as 1. 
Next, an amplification factor m is set using the average value V0 of the 
image data (Step S3) and preparatory light is generated at this 
amplification factor m in compliance with the CPU 8 (Step S4). 
Thereafter, the A/D circuit 6 A/D converts the image data (Step S5), which 
is then stored in the memory 7 (Step S6). 
Next, the average value V1 of the image data using preparatory light is 
determined (Step S7). Now, the amplification factor of the amplifier 4 is 
set to 1. 
Thereafter, it is determined whether the average value V1 of the image data 
using preparatory light is between predetermined values .alpha. and .beta. 
(Step S8). When .alpha.&lt;V1&lt;.beta., the CPU 8 calculates an amount of 
actual light to be generated (Step 9). The method of this calculation will 
be explained in detail later. 
Thereafter, the CPU 8 controls the opening and shutting of the shutter 2, 
causes the strobe light-generating tube 13 to generate light (Steps S10, 
S11 and S12), and captures image data from the CCD 3 (Step S13). 
Next, the method for calculating the amount of actual light generated 
according to the first embodiment will be explained. 
Firstly, as described above, after determining the average value V0 of 
image data obtained using natural light and setting the amplification 
factor accordingly, the average value V1 of image data using preparatory 
light is determined. Then, after the average value V2 of the image data 
after amplification has been determined, an appropriate level V3 of image 
data using actual light generation is determined. Actual light generation 
is carried out using an amplification factor of 1. 
The amplification factor is set to 1 when generating preparatory light, as 
described above, in order to reduce as much as possible the amount of 
energy wasted by the strobe when generating preparatory light, and thereby 
more accurately calculate the amount of actual light to be generated. 
Furthermore, the amplification factor is set to 1 when generating actual 
light in order to obtain noiseless image data. 
Thus, having determined each value, since the average output of image data 
obtained using actual light generation is V3-V0, the actual light 
generated is K times the preparatory light, that is: 
EQU K=(V3-V0)/V1 
where V1=(V2/m)-V0. 
In fact, the CPU 8 determines the time of actual light generation by 
referring to an LUT (Look Up Table) in which the relation between K and 
light generating time (t) is stored. 
When measuring using only natural light or preparatory light, the entire 
screen can be partitioned into 64 regions so that the image pickup element 
need only determine data comprising the average of pixel data in each 
region calculated using the hardware. This method enables processing to be 
performed at high speed. 
According to the strobe device of the first embodiment, image data of an 
appropriate level can be obtained when generating actual light. 
Next, a second embodiment of the present invention will be explained. 
The strobe device of the second embodiment has the same configuration as 
the first embodiment already described, and differs only with respect to 
the operation of calculating the amount of light based on preparatory 
light generation. Therefore, mention will be made only to the differences 
between the embodiments; detailed explanation of identical parts will be 
omitted. 
FIG. 3 shows a flowchart illustrating the operations of calculating the 
amount of actual light to be generated using preparatory light generation 
and photographing according to the strobe device of the second embodiment. 
As shown in FIG. 3, when the release switch 15 turns ON (Step S1), firstly, 
image data using only natural light is input and the CPU 8 determines the 
average value V0 of this natural light image data (Step S2). From this 
point up to Step S6, the process is identical to the first embodiment 
already described, and explanation will here be omitted. 
Next, it is determined whether or not preparatory light has been generated 
N times (Step S21). When preparatory light has been generated N times, an 
average value Vm of the image data of each preparatory light generation is 
calculated (Step S22), and it is determined whether the average value Vm 
of the image data of each preparatory light generation is between 
predetermined values .alpha. and .beta. (Step S23). When 
.alpha.&lt;V1&lt;.beta., the CPU 8 calculates an amount of actual light to be 
generated (Step 9). The method of this calculation is the same as in the 
first embodiment described above. 
Thereafter, the CPU 8 controls the opening and shutting of the shutter 2, 
causes the strobe light-generating tube 13 to generate light (Steps S10, 
S11 and S12), and captures image data from the CCD 3 (Step S13). 
According to the strobe device of the second embodiment, image data of an 
even more appropriate level can be obtained when generating actual light. 
Next, a third embodiment of the present invention will be explained. 
FIG. 4 is a block diagram showing the configuration of the strobe device 
according to the third embodiment of the present invention. Like 
configuration elements to the first embodiment are designated by like 
reference characters and explanation is omitted here. 
The basic configuration of strobe device of the third embodiment is the 
same as the first embodiment described above, but is characterized in that 
the amount of preparatory light generated is calculated based on distance 
measurements taken by a distance-measuring circuit 21. 
FIG. 5 shows a flowchart illustrating operations of calculating an amount 
of actual light to be generated using generation of preparatory light and 
photographing in the strobe device according to the third embodiment. 
The strobe device of the third embodiment is characterized in that distance 
to the subject is measured prior to generating preparatory light and the 
amount of preparatory light generated is calculated based on this distance 
measurement. 
As shown in FIG. 5, when the release switch 15 turns ON (Step S1), firstly, 
image data using only natural light is input and the CPU 8 determines the 
average value V0 of this natural light image data (Step S2). 
Next, a distance-measuring circuit 21, controlled by the CPU 8, measures 
the distance to the subject (Step 31). Then, the amount of preparatory 
light needed to be generated is calculated based on this measurement (Step 
S32) and the amplification factor m is set based on the amount of light 
calculated (Step S3). 
That is, by measuring the distance to the subject, it is possible to set 
more light to be generated when the subject is farther away than when the 
subject is at close range. The amount of light generated may be set in 
proportion to the square of the distance to the subject. Or, it may be set 
to a suitable value determined by experience. 
Next, preparatory light is generated based on the amplification factor m in 
compliance with the CPU 8 (Step S4). Thereafter, the A/D circuit 6 A/D 
converts the image data (Step S5), which is then stored in the memory 7 
(Step S6). 
Next, the average value V1 of the image data using preparatory light is 
determined (Step S7) and the CPU 8 calculates the amount of actual light 
to be generated (Step 9). The method of calculation is the same as in the 
first embodiment described above. 
Thereafter, the CPU 8 controls the opening and shutting of the shutter 2, 
causes the strobe light-generating tube 13 to generate light (Steps S10, 
S11 and S12), and captures image data from the CCD 3 (Step S13). 
According to the third embodiment, an optimum amount of preparatory light 
can be generated in accordance with the distance to the subject, enabling 
a still more optimum amount of light to be obtained. 
Next, a fourth embodiment of the present invention will be explained. 
FIG. 6 is a block diagram showing the configuration of the strobe device 
according to a fourth embodiment of the present invention. Like 
configuration elements to the first embodiment are designated by like 
reference characters and explanation of such like elements is omitted 
here. 
The basic configuration of the fourth embodiment is the same as the first 
embodiment described above, but is characterized in that the amplifier 4 
is omitted and the amount of preparatory light generated is calculated 
based on distance measurements. 
FIG. 7 is a flowchart showing operations of calculating an amount of actual 
light to be generated using preparatory light generation and photographing 
according to the strobe device of the fourth embodiment. 
In the strobe device of the present embodiment, the distance to the subject 
is measured prior to generating preparatory light, as in the third 
embodiment, and the amount of preparatory light generated is calculated 
based this distance measurement. 
As shown in FIG. 7, when the release switch 15 turns ON (Step S1), firstly, 
image data using only natural light is input and the CPU 8 determines the 
average value V0 of this natural light image data (Step S2). 
Next, the distance-measuring circuit 21, controlled by the CPU 8, measures 
the distance to the subject (Step 31). Then, the amount of preparatory 
light needed to be generated is calculated based on this measurement (Step 
S32). 
That is, by measuring the distance to the subject, it is possible to set 
more light to be generated when the subject is farther away than when the 
subject is at close range. The amount of light generated may be set in 
proportion to the square of the distance to the subject. Or, it may be set 
to a suitable value determined by experience. 
Next, preparatory light is generated in compliance with the CPU 8 (Step 
S4). Thereafter, the A/D circuit 6 A/D converts the image data (Step S5), 
which is then stored in the memory 7 (Step S6). 
Next, the average value V1 of the image data using preparatory light is 
determined (Step S7) and the CPU 8 calculates the amount of actual light 
to be generated (Step S9A). The method of calculation will be explained 
later. 
Thereafter, the CPU 8 controls the opening and shutting of the shutter 2, 
causes the strobe light-generating tube 13 to generate light (Steps S10, 
S11 and S12), and captures image data from the CCD 3 (Step S13). 
Next, the method for calculating the amount of actual light to be generated 
according to the fourth embodiment will be explained. 
Firstly, as described above, the average value V0 of image data obtained 
using natural light and the average value V1 of image data using 
preparatory light are determined. Then, the appropriate level V3 of image 
data for actual light generation is set to a suitable value, determined by 
experience or the like. 
Thus, having determined each value, since the average output of image data 
obtained using actual light generation is V3-V0, the actual light 
generated is K times the preparatory light, that is: 
EQU K=(V3-V0)/V1 
where V1=(V2/m)-V0. 
In fact, as in the embodiments already described, the CPU 8 determines the 
period of actual light generation by referring to an LUT (Look Up Table) 
in which the relation between K and light generating time (t) is stored. 
According to the strobe device of the fourth embodiment, an optimum amount 
of actual light generated can be obtained without providing an amplifier. 
As explained above, according to the present invention, it is possible to 
provide a strobe device capable of obtaining an optimum amount of actual 
light generated by generating preparatory light. 
In this invention, it is apparent that working modes different in a wide 
range can be formed on this basis of this invention without departing from 
the spirit and scope of the invention. This invention is not restricted by 
any specific embodiment except as may be limited by the appended claims.