JPH0420946A - strobe device - Google Patents

Abstract

PURPOSE:To effectively prevent a red-eye phenomenon with a proper quantity of light, to obtain the proper quantity of light at the time of photographing, and to use a light emission start voltage in a wide range by using the voltage of a main capacitor to control the quantity of emitted light. CONSTITUTION:The voltage of a battery 11 is raised by a boosting circuit 12 and electric charge is stored in a main capacitor 1. Meanwhile, the voltage of the main capacitor 1 is divided by a voltage dividing resistance 3 (R1 and R2), and a divided voltage VA is inputted to not only an A/D c 7 but also the + terminal of a comparing means 8. An output voltage VD of a D/A C 6 is inputted to the - terminal of the comparing means 8. A voltage proportional to the voltage of the main capacitor 1 at the time of the end of light emission, namely, the same voltage as the voltage VA for the end of light emission is set as the voltage VD. When a light emission start signal is turned on, an Xe tube 2 is excited by a trigger means 10 to start light emission. When the Xe tube 2 emits light, the voltage of the main capacitor 1 is quickly reduced and the voltage V is reduced also. When the voltage VA is reduced to be lower than the voltage VD, the comparing means 8 is inverted and a light emission stop means connected in series to the Xe tube 2 is started to stop the light emission of the Xe tube.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for photographing with a strobe light in a camera, and particularly to an auto strobe control device having a red-eye prevention function.

(Prior Art) There is a so-called red-eye phenomenon in which the pupil of the human eye turns red during strobe (flash) photography. There are two methods to prevent (reduce) this:

■ Increase the angle between the center of the light emitting section, the subject (eyes), and the photographic lens.

■ Prior to photographing, the subject (eye) is illuminated to make the pupil smaller and then the photograph is taken.

In order to increase the interpolation angle (■) above, it is necessary to increase the distance between the light emitting part and the photographing lens.

This is difficult to do with a compact camera with a built-in strobe, and is shown in Japanese Patent Publication No. 58-48088 and Shashin Kogyo, December 1989 issue 78, which is difficult to do with a compact camera with a built-in strobe. Those shown on pages 1 to 79 are known.

The one published in Japanese Patent Publication No. 5g-48088 makes the subject's pupil smaller by lighting up a lamp before taking a strobe shot, and the one published in the December 1989 issue of Shashin Kogyo pre-fires the strobe multiple times before taking a strobe shot. This is to make the subject's pupil smaller.

(Problems to be Solved by the Invention) However, the method disclosed in Japanese Patent Publication No. 58-48088 requires an irradiation member in addition to the strobe, which poses problems in terms of cost and space. Also photo industry 1989
The one described in the December issue has the advantage of not requiring an irradiation member separate from the strobe, but since the pre-flash repeatedly emits a small amount of light, unlike conventional strobe devices, it integrates the amount of reflected light and emits light according to its level. It is difficult to stop the light, so the amount of light is adjusted by controlling the emission time.

If the flash start voltage changes or the start-up characteristics at the time of flash change, the amount of light obtained changes, resulting in problems such as not being able to achieve the desired red-eye prevention effect, or causing the subject's eyes to blur due to one flash being too strong. . Furthermore, there is a problem in that variations in the total amount of light during pre-emissions directly result in variations in the amount of light emitted during main emission during photographing, which hinders detailed photographing.

The present invention solves the above-mentioned conventional problems, and enables pre-emission with no variation in light intensity, and is unaffected by the reflectance of the subject, and even with large changes in the emission start voltage.
The purpose of the present invention is to provide an autostroboscopic device that can control the amount of light to a desired level.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a strobe device that:
A means for measuring the voltage of the main capacitor, a light amount calculating means for calculating the amount of light necessary for illuminating the subject, and a means for measuring the voltage of the main capacitor after emitting light with the amount of light calculated by the light amount calculating means before emitting light. A voltage calculation means for calculating, a resistor voltage dividing means for outputting a voltage proportional to the voltage of the main capacitor, a D/A converter for outputting a voltage proportional to the voltage obtained by the voltage calculation means, and a voltage proportional to the voltage of the main capacitor. Comparison means for comparing the voltage obtained by the voltage calculation means with a voltage proportional to the voltage obtained by the voltage calculating means, and stopping the light emission when the voltage divided by the resistor voltage dividing means after the flash is released becomes lower than the output voltage of the D/A converter. The output voltage of the D/A converter is reset each time the strobe light is emitted. Also, before the strobe fires, the voltage of the main capacitor after each flash is calculated and stored in the storage means, and the output of the D/A converter is set according to the value in the storage means each time the strobe is fired. This is what I tried to do again.

(Function) Therefore, according to the present invention, the amount of emitted light is controlled using the voltage of the main capacitor.

It is possible to effectively prevent red-eye with an appropriate amount of light, obtain an appropriate amount of light during shooting, and use a wide range of light emission start voltages. In addition, by storing the value of the main capacitor after flashing for all multiple flashes before flashing, it eliminates the need for measurement calculations during strobe flashing, and improves the time management of the control unit (CPU) in flash control. can be facilitated.

(Embodiment) FIG. 1 shows the configuration of a strobe device in an embodiment of the present invention. In Figure 1, 1 is the main capacitor, 2 is the xenon arc tube (hereinafter referred to as "xenon arc tube").

(referred to as a Xe tube), 3 is a voltage dividing resistor that divides the voltage of the main capacitor l, 4 is a light amount calculation means that calculates the amount of light necessary for illuminating the subject, and 5 is a light emission calculated by the light amount calculation means 4 before emitting light. 6 is a digital-to-analog converter (D/A/C); 7 is an analog-to-digital converter (A/D/C); 9 is a comparison means, 9 is a light emission stop means that stops light emission when the voltage of the voltage dividing resistor 3 becomes lower than the output voltage of D/A-06 after the flash is released, 10 is a trigger means for the Xe tube 2, 11 is a power source, and 12 is a light emission stop means. boost circuit,
13, 14, and 15 are distance information, film sensitivity information, and aperture information that are input to the light amount calculation means 4. 16 is the base guide number (G No.) information, and 17 is a light emission control means.

Next, the operation of the above embodiment will be explained. In the embodiment described above, the voltage of the battery 11 is boosted by the booster circuit 12 and charge is stored in the main capacitor 1. on the other hand.

The voltage of main capacitor 1 is determined by voltage dividing resistor 3 (R construction).

R2), and the voltage (VA) is divided by the A/D.
It is input to C7 and also to the (+) terminal of comparison means 8. The output voltage (VO) of the D/A/C 6 is input to the (-) terminal of the comparing means 8. vI is a voltage proportional to the voltage of the main capacitor 1 at the end of light emission, that is, set to the same voltage as vA at the end of light emission.6 When the light emission start signal (not shown) is turned on, the trigger means 10 sets Xs.
Tube 2 is excited and starts emitting light. When the Xs tube 2 emits light, the voltage of the main capacitor 1 rapidly decreases, causing v
A also decreases.

■When A becomes lower than VD, the comparison means 8 is inverted and
The light emission stopping means connected in series with the e-tube 2 is activated to stop the light emission of the Xe tube 2. Thereafter, the voltage of VD is changed and set, and the Xe tube 2 is repeatedly turned on and off in the same manner as above to complete the pre-light emission.

When the pre-emission is completed, the VD voltage necessary for photography is set and the shutter is opened (not shown), and the trigger means 10 excites the Xe tube 2 and starts emitting light. As IIVA decreases, vA also decreases. When IIVA decreases below VD, the comparing means 8 reverses, starts the emission stopping means 9 connected in series with the Xe tube 2, and stops the emission of light from the Xe tube 2. This operation is completed by closing the shutter.

Next, a calculation method for setting the VD in the above embodiment will be explained (see FIG. 2).

Now, the voltage of the main capacitor when fully charged is (VIO), and the residual voltage of the main capacitor after full light emission is (Va.) = The amount of light when light emission starts at Vio and stops at v7o is the full light amount. (GNo, .) as the amount of emitted light (guide N00). Also, if the distance from the camera to the subject is (D), the aperture value of the lens is (F), and the amount of light emitted (guide No. F --(1) If you try to give the same amount of light to a unit area with a strobe light, and if the energy emitted by the strobe is E, then EO:D''... (2)
Also, since DαGNo, ...(3), EocGNo,'' --(4).

■,. , vTo is the energy emitted by E, and the proportionality constant is K, then the voltage of any main capacitor before the start of light emission is V I
X PAlso, if the voltage when the light emission is stopped is v7x, the energy Ex obtained at this time is GNo,
x is the guide No. to obtain the amount of light necessary for photographing, and the required G N is the reference G No.
Let the ratio of GNo, , which is o, be X.

and Therefore.

When equation (8) is solved for the light emission stop voltage v1x, v,
"==v,,"-x"" (V, "-Vta")...
...(9) Or, the voltage obtained by lowering the voltage values of v and x obtained by equation (9) or equation (10) by the same ratio as the voltage division ratio determined by resistors R8 and R2 in Figure 1 is D/ It is output as the voltage V at the time of the first emission start, which is the output of A-C (FIG. 1, 6).

Namely.

Furthermore, in order to simplify equation (9), V. =y−■,.

Then, V, x"==V, x"-x"(1-y")Vm. '...
(12) ■ t0 is the residual voltage at full light emission, and vIo is the voltage at full charge, so for example, ■. =40V.

■,. = 330 V, then y = 1 block r clause 0.12
Therefore, if (1-y") square 1, equation (12) becomes Vy-"=v,
x''-x''■, -'' --(13).

Furthermore, if you manage to make vIx always emit light with vlo.

V, x”=(1-x”)V,. '...
...(14).

Although vo was calculated as the voltage of the main capacitor when fully charged, v7゜ is not limited to the voltage when fully charged; it can be any voltage as long as it can emit light; in short, it can be any known voltage. Guide no.

Any voltage corresponding to is sufficient, and even in this case, the above calculation formula can be applied as is without affecting it at all. The same thing can be said about VTO as well.

From the above, ■ Main capacitor voltage before light emission (v
mx) is the measurement, ■ Main capacitor voltage after light emission (Vt
By performing the pre-light emission and the present invention by repeating the calculation of x), (1) setting the stop voltage with D/A-C, (2) light emitting operation, and the above steps (2) to (4), it is possible to accurately provide the amount of light to the subject.

In addition, ■Measurement of the main capacitor (vm-) before pre-emission, calculation of main capacitor stop voltage (V t Calculate the stop voltage (Vtxtm*zz) after the main light emission and store the results in the memory sequentially.◎Setting the stop voltage with D/A-C, ■Light emission operation, ■Memory contents determined in [Yes] above It is also possible to emit light by calling sequentially and repeating the operations of ◎ to
, * V t□. ,...,Va1. , then, for example, the stop voltage after the first light emission is Vt! +□)
Therefore, this is nothing but the voltage before the second light emission. By multiplying this by the next v and x, the next stop voltage can be found from equations (9) and (10).

Similarly, the stop voltage after main emission is V? If x1m*xl, then the nth pre-emission stop voltage V? xla) can be calculated as Vtxlxr*x from the amount of light required for photographing with 7 apertures. This situation is shown in FIG.

(Effects of the Invention) As is clear from the above embodiments, the present invention controls the amount of emitted light using the voltage of the main capacitor, so it is possible to effectively prevent red-eye by pre-emitting light with an appropriate amount of light. It has the advantage of being able to realize an auto strobe with an appropriate amount of light when photographing, and also being able to utilize a wide range of light emission start voltages.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a strobe device according to an embodiment of the present invention, Fig. 2 is a diagram showing voltage changes of the main capacitor when pre-flash is not performed in an embodiment of the present invention, and Fig. 3 is a block diagram of a strobe device according to an embodiment of the present invention.
The figure is a diagram showing the voltage change of the main capacitor when pre-emission is performed in one embodiment of the present invention. 1...Main capacitor, 2...Xe tube, 3
...Voltage dividing resistor, 4... Light amount calculation means, 5...
Voltage calculating means, 6... Digital-to-analog converter (D/A-C), 7... Analog-to-digital converter (A/D-C), 8... Comparing means,
9...Emission stop means, 10...Trigger means, 1
1... Power source, 12... Boost circuit, 13... Distance information, 14... Film sensitivity information, 15... Aperture information, 16... Base guide number information, 17...
- Light emission control means.

Claims (2)

[Claims] (1) In response to a camera release signal, one or more light emitting operations are performed for pupil constriction immediately before the shutter opens and closes, and after the shutter starts opening and closing, light is emitted for photographing. , a strobe that illuminates a subject by discharging electric charge stored in a main capacitor in an arc tube, comprising: means for measuring the voltage of the main capacitor; and a first calculating means for calculating the amount of light necessary for illuminating the subject; a second calculation means for calculating the voltage of the main capacitor after emitting light of the amount of light determined by the first calculation means before emitting light; and outputting a first voltage proportional to the voltage of the main capacitor. a first output means, a second output means that outputs a second voltage proportional to the voltage determined by the second calculation means, and a comparison means that compares the first voltage and the second voltage; A strobe device comprising a light emission stopping means for stopping light emission when the first voltage becomes lower than a second voltage after flash emission, and the output of the second voltage is reset each time the strobe light is emitted. (2) Before flashing the strobe, a storage means is provided for calculating the voltage of the main capacitor after flashing for all of the multiple flashes and storing that value, and a second voltage is calculated each time the strobe fires according to the value in the storage means. 2. The strobe device according to claim 1, wherein the output of the strobe is reset.