JPH0478833A - Light emission controller - Google Patents

Abstract

PURPOSE:To offer a light emission controller for controlling the light emission of a storoboscope so that optimum exposure can be applied for a human figure by releasing the inhibition of the light emission of the stroboscope in the case that photographing magnification is equal to or exceeding a prescribed value. CONSTITUTION:A controller is provided with a photographing magnification calculating means CPU 1 for obtaining the photographing magnification for an object by the use of the outputs of a distance detecting means 10 and a focal distance detecting means 20. In the case that the photographing magnification is equal to or exceeding the prescribed value, the inhibition of the light emission of the stroboscope is released by the CPU 1. In the light emission controller, the photographing magnification is used as the reference for judging whether the light emission of the stroboscope is permitted or not. That means, in the case of taking the photographing magnification with which the human figure is certainly photographed, the strobe light is emitted even in the case that the object has high brightness. Thus, since the inhibition of the light emission of the stroboscope is released in the case that the photographing magnification is within the extent of the photographing magnification in a normal use for photographing the human figure even in the case that the brightness of the object is higher than the prescribed value, the optimum exposure can be applied for the human figure even in the case that the portrait of the human figure in a follow light state is photographed with top light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light emission control device, and more particularly, to a light emission control device for controlling strobe light emission in a camera having a low-brightness automatic light emission strobe.

[Prior art] In addition to the conventional automatic flashing at low brightness, in strobe devices, by determining the average brightness and partial brightness of the subject, the camera automatically detects backlight conditions and fires the strobe. For example, the Special Publication Act of 1984-294
It is disclosed in No. 08. In this case, the light emission judgment is as follows: The O mark indicates permission and the X mark indicates prohibition.
It will look like a table.

Table 3 [Problems to be Solved by the Invention] However, by determining the average brightness and partial brightness, the camera automatically detects backlight conditions and fires a strobe light. -29
In the technical means disclosed in No. 408, for example, when a portrait of a person in front light is taken in a top light condition,
If there is strong light from above, the shadows on the face will be strong, resulting in a photo with a poor expression. To correct this, experienced users use strobe light in combination, but this is a fairly difficult photographing technique for novice users.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a light emission control device that controls strobe light emission so that the person is properly exposed when photographing a person using a camera equipped with a low-brightness automatic light emission strobe. There is something to do.

[Means for Solving the Problems] A light emission control device of the present invention is a light emission control device that prohibits a strobe device from emitting light when the brightness of a subject is higher than a predetermined value, and includes distance detection means for detecting a distance to a subject. , a focal length detecting means for detecting the focal length of the photographing lens; a photographing magnification calculating means for calculating a photographing magnification of the subject using the outputs of the distance detecting means and the focal length detecting means; and when the photographing magnification is equal to or greater than a predetermined value; The present invention is characterized by comprising a light emission prohibition canceling means for canceling the light emission prohibition of the strobe device.

[Operation] This light emission control device uses photographic magnification as a criterion for determining whether or not to emit strobe light. That is, at a photographing magnification where there is a strong possibility of photographing a person, the strobe is set to emit light even if the subject is of high brightness, for example.

[Example] The present invention will be specifically described below with reference to the drawings. 1st
The figure is a circuit configuration diagram of an electric circuit of a light emission control device showing one embodiment of the present invention, and will be described below as an example applied to a camera with a zoom function. In the figure, this light emission control device includes a distance detecting means 10 for detecting the subject distance, a focal length detecting means 20 for detecting focal length information of the photographing lens, a photometering means 30 for metering the subject brightness, and a strobe light emission control device. The CPU comprises a flash light emission control means 40, which performs sequence control over the operations of the above-mentioned means, and has photographic magnification calculation means, light emission prohibition release means, etc. formed on a control program.

To explain the distance detecting means 10, the distance measuring circuit 1
The infrared light emitted from the infrared LED 14 whose light emission is controlled by 5 is focused by the projection lens 13 and irradiated onto a subject (not shown). The reflected light reflected by the subject is imaged by a light receiving lens 11 onto a light receiving surface of a PSD (semiconductor device detector) 12. The distance measuring circuit 15 is connected to this PSD.
The distance g to the subject is calculated from the photocurrent of No. 12 using known means.

The focal length detection means 20 includes a focal length detection circuit 21 and a potentiometer 22, and uses a zoom mechanism (not shown) to calculate the focal length f of the photographic lens from the resistance value of the potentiometer 22 that is linked to the zoom operation.

The distance g to the subject and the focal length f of the photographic lens described above are transmitted to the CPUI. Then, CPUI changes these two values 1. From f, the imaging magnification β is determined from β-C1/f)-2. In this case, for simplicity, it may be assumed to be β-.

The photometry circuit 31 of the photometry means 30 includes a light receiving element 3 for average photometry.
2 are connected. This light-receiving element 32 for average photometry measures the subject light via the lens 34 for average photometry, and the obtained photometry result is transmitted to the CPUI.

Next, the flash light emission control means 40 that controls strobe light emission will be explained. When the signal output to output port 01 of the CPUI becomes H-L, transistor Q103 of the strobe circuit is turned on via resistor R103, thereby transistors Q101, Q102 . Resistance RIOI,
A well-known DC/DC humbverter circuit configured by connecting R102 and a step-up transformer T101 as shown in the figure oscillates, and main capacitor C101 is charged via diodes DIOI and D102.

Resistors R1, R2 and capacitor C1 divide almost the same voltage as main capacitor C101, and the CPU A/D
Enter in input port ■1. This allows the CPUI to monitor the charging voltage of the main capacitor C101 at any time. Here, main capacitor Cl0I,) trigger transformer TlO2, capacitor C1
0B.

Resistor R109, IGBT (Insulated
Gate Bipolar Transistor)
Q 104 forms a trigger circuit for the Xe tube 22. This IGBT Q104 is an element that can instantaneously control a large current by setting the gate voltage to H.

Next, a light emission control circuit for the Xe tube 22 will be explained. Resistors R104, R105, R109, IGBTQ104.
The capacitor C102 and the diode D104 are a voltage doubler circuit, that is, by applying a voltage twice the voltage across the main capacitor c1o1 between A- of the Xe tube 22 at the time of light emission, the light emission starting voltage of the Xe tube 22 is lowered. It is something to hold down.

Transistor Q105. Q106. Q107゜Q108
receives the light emission signal from the output port 02 of the CPUI and controls the gate of the IGBT Q104. Diode D103. Resistor RIIO, constant voltage diode Z
9. The capacitor ClO4 is a power supply circuit for generating the gate voltage of the IGBT Q104.

When the light emission signal from the output port 02 of the CPUI is not applied to the resistor R108, the transistor Q108. Q107
．． Q106 is off and the gate of IGBT Q104 is not biased. On the other hand, when a light emission signal is applied from output port 02 of CPUI, transistor Q
108°Q107. Q106 turns on and transistor Q
105 is turned off, IGB is connected through resistor R106.
The gate of TQ104 is biased to H. The capacitor ClO3 is charged in advance to the voltage across the main capacitor C101 through the resistor R104, and the capacitor ClO2 is similarly charged to the voltage across the main capacitor C101 through the resistor R104, R105,
The voltage across the main capacitor C101 is precharged through R109.

When IGBTQ104 is turned on, the charge in capacitor 0103 is transferred to trigger transformer Tl through IGBTQ104.
is discharged to the primary side of O2, thereby causing the same transformer Tl
High pressure is generated on the secondary side of O2 to ionize the Xe tube 22. At the same time, through the capacitor ClO2, the Xe tube 2
2 cathode to -Vc1o1, so that X
A voltage of 2vc1o1 is applied between the A- terminal of the e-tube 22, so that the Xe tube 22 can easily emit light. Then, when the Xe tube 22 starts emitting light, the light emitting current is C1
01 → Xe tube 22 → D104 → C101 and discharge
The e-tube 22 emits light. After that, when the light emission signal output from the output port 02 of the CPUI becomes L level, the transistor 010g.

Q107. Q106 turns off and at the same time transistor Q1
05 turns on. Therefore, the gate of IGBTQ104 is shorted by transistor Q105, and IGBTQ10
4 is off. Therefore, capacitor 0103 has Xe
An electric charge is instantly charged through the tube 22, and at the same time the Xe tube 22 stops emitting light. Preparation for the next light emission ends at the same time as this light emission. That is, in this circuit, the IGBTQ 104 has three functions: a trigger circuit for light emission, a voltage doubler circuit, and a main switch element for light emission. The above is a description of the flashlight emission control means 40 used in this embodiment.

This allows the guide number of the strobe to be freely controlled.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. In FIG. 2, first, the distance g to the subject measured by the distance detecting means 10 shown in FIG. 1 is defined as the strobe light reach limit distance p.

(Step SL). If 1>1° in this step S1, it means that the subject exists outside the reachable range of the strobe light, so in order to prevent unnecessary strobe light emission, jump to step S8, turn off the strobe light flag, and return. do.

The strobe light reach limit distance N1o is determined by Gmax, which is the maximum guide number of the strobe, and F, which is determined by external light.
If the number is F, then GN.

gO'''' (obtained from ZX F. Here, if α is 2, strobe light emission is permitted until the main subject is 4Ev below, and strobe light emission is prohibited beyond that point.

Next, it is checked whether the photometric level Ev received by the light receiving element 32 is lower than a predetermined photometric level A, that is, whether the luminance is low (step S2). The predetermined photometry level A corresponds to a determination value in conventional low-luminance automatic light emission. If it is determined in step S2 that the subject has low brightness, the strobe light emission flag is turned on (step S3), and the guide number GNo is calculated using the usual guide number calculation formula % (step S4).

Returning to step S2 above, if it is determined that the subject is not of low brightness, then the photographing magnification β is set to the photographing magnification β1, which is often used for photographing people. It is determined whether the value is between β2 or not (step S7). In this case, it is sufficient to set the value to approximately β1-1/20 β2-1/80, and since daytime synchronized photography is a technique used in most cases when photographing a person under backlight, the above step S7 It is possible to determine whether the strobe is on or off based on the criteria.

When the photographing magnification β corresponds to the magnification normally used when photographing a person, the strobe light emission flag is turned on (step S5), and the guide number calculation is shifted to the IEv under side, that is, 1/4 times (step S6). . The reason for this is that if the guide number calculation is performed normally as in step S4 above when there is constant light, the subject person will often stand out in white and look unnatural. On the other hand, returning to step S7 above, if the photographing magnification does not correspond to the magnification normally used when photographing a person, the strobe light emission flag is turned off and step S8
), return.

Since the above-described flow determines whether strobe light is to be emitted or not and the guide number GNo, it is sufficient to control the output port 02 of (:PUl) shown in FIG. 1 in the photographing sequence.
If the photographing magnification β is within the range of magnifications normally used when photographing people, that is, β1>β>β2, as shown in Table 1, outside the range of magnification, i.e. β〉β, β
If 2>β, then the results are as shown in Table 2 below. However, the O symbol indicates strobe light emission, and the X symbol indicates non-emission.

Table 1 Note that in the above embodiments, explanations have been made assuming a camera with a zoom function, but since the focal length of a single-focal or focal-switching type camera is fixed, the present invention is When used in a camera of this type, the focal length detection means 20 shown in FIG. 1 can be simplified. In this case, if the focal length information is stored in the memory of the CPUI, it is possible to determine whether the photographing magnification is a magnification used for photographing a person simply by determining the subject distance.

According to the above-described embodiments, (1) Even beginners can reduce unsightly shadows that appear on the face when attempting to take pictures under direct light, especially with top light.

■When the brightness of the subject is higher than a predetermined value and strobe light emission is unnecessary, or when the subject is outside the reachable range of the strobe light and firing the strobe light has no effect, the strobe does not fire, which reduces battery consumption. can be prevented.

[Effects of the Invention] As described above, according to the present invention, even if the brightness of the subject is higher than a predetermined value, if the photographing magnification is within the range of magnification normally used when photographing a person, the strobe device is prohibited from emitting light. By canceling this function, for example, when photographing a portrait of a person in front light using a top light, a remarkable effect can be achieved in that the correct exposure can be given to the person.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an electric circuit of a light emission control device showing one embodiment of the present invention, and FIG. 2 is a flowchart of the strobe light emission operation in FIG. 1. 1... CPU (imaging magnification calculation means 2 flash prohibition release means) 10... distance detection means 20... focal length detection means

Claims (1)

[Claims] (1) A light emission control device that prohibits flash emission of a strobe device when the brightness of the subject is higher than a predetermined value, which includes a distance detection means for detecting the distance of the subject, and a focal length detection means for detecting the focal length of the photographic lens. , a photographing magnification calculating means for calculating a photographing magnification of a subject using the outputs of the distance detecting means and the focal length detecting means; and a flash prohibition canceling means for canceling the prohibition of flash of the strobe device when the photographing magnification is equal to or higher than a predetermined value. A light emission control device comprising: