JP3217410B2 - Multi-flash light metering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-flash strobe light metering system, and more particularly to a multi-strobe flash metering system which makes effective use of a built-in main capacitor of a strobe light emitting circuit by pre-strobe light.

[0002]

2. Description of the Related Art When photographing by flash emission, photometry by pre-flash with flash emission is performed in advance to measure subject conditions (exposure conditions, etc.) before actual shutter release for actual photography. After deciding the shooting conditions in this way, firing the flash for actual shooting,
A so-called multi-flash metering system is known. Japanese Patent Publication No. 1-37072 discloses an imaging apparatus which presets the gain of an imaging signal in advance for flash photography and corrects this gain in actual photography to obtain a wide dynamic range. In order to perform pre-flash photometry, an external photometric light-receiving unit for photometry is usually provided on the lens surface side of the camera body. The photographing conditions such as the focal length and the focal length are determined.

[0003]

As the power for strobe light emission, the charging power of the main capacitor incorporated in the strobe light emitting circuit is used. However, since the capacity of the main capacitor is limited, the pre-charge power is limited. If a large amount of power is consumed during a photometric operation by light emission, charging cannot be performed in time, and power required for strobe light emission during actual shooting cannot be supplied. In such a case, there is a serious problem that a shutter chance at the time of actual shooting is missed. In particular, in the conventional multi-flash light metering system, the light emission amount is obtained based on the light measurement signal level obtained in the first pre-flash. Cannot be estimated, and the video image is in an underexposed or overexposed state. This means that in order to obtain an appropriate amount of light, pre-emission must be performed many times, power consumption increases, and charging during actual shooting cannot be performed in time.

Accordingly, an object of the present invention is to reduce the amount of discharge at the time of pre-emission using a main capacitor for strobe emission,
An object of the present invention is to provide a multi-flash light-metering system which enables a reliable strobe operation at the time of actual shooting and does not miss a photo opportunity. It is another object of the present invention to provide a multi-flash light metering system which can reduce the size and cost of a main capacitor for strobe light.

[0005]

In order to solve the above-mentioned problems, a multi-flash light metering system according to the present invention comprises:
A multi-flash light metering system for obtaining photometric information suitable for the image recording using the projection light from the flash light emitting unit based on an output of the photometric unit relating to the projection light by the pre-flash prior to the image recording. , Subject
Means for obtaining distance information, the calling based on the distance information
Means for determining the amount of light, and the main condensation of the flash light emitting means
And means for detecting a charging voltage of the service, the charging voltage and the onset
Based on the amount of light and pre-emission for the flash emission means
Means for setting the light emission time at the time .

[0006]

According to the present invention, a light emission amount that is relatively close is obtained based on distance information, and a light emission time during pre-emission is set based on the obtained light emission amount and the charging voltage of the main capacitor. By performing light emission, the discharge due to pre-emission at the time of photometry of the main light emitting capacitor is minimized,
The power consumption is reduced, and a high-speed appropriate light emission amount is obtained.

[0007]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a multi-flash light metering system according to the present invention, showing an example of an electronic still camera employing an imager metering method.
A subject image is formed on an image sensor (CCD) 2 via an optical lens system and an aperture 1. The electric signal obtained from the CCD 2 is sent to an AGC (automatic gain control) unit 4 as an image signal from which unnecessary components have been removed by a CDS (correlated double sampling) unit 3. The AGC unit 4 adjusts the image signal level to an appropriate level, and is configured by a variable gain amplifier. The output image signal from the AGC unit 4 is subjected to predetermined processing such as γ correction and extraction of a luminance signal and a color signal in an imaging process unit 5. The obtained luminance signal and color signal are
FM-modulated by the M modulator 6 and the REC amplifier (REC A
After being amplified by the MP 7, it is recorded on a recording medium 9 such as a magnetic disk, a recording tape (video tape), or an IC card via a head 8.

The system controller 13 controls the diaphragm 1
Control signal for controlling the signal charge accumulation time of the CCD 2, that is, a shutter speed control signal for controlling a drive unit (DRV) 10 for driving a so-called element shutter, and a gain of the AGC unit 4 are set. Signal necessary for the camera operation, such as a gain control signal for the camera, is sent to each unit. If necessary, the system controller 13
The AF auxiliary light source unit 17 operates according to the light emission command signal from the camera. The reflected light from the subject obtained by the emission of the AF auxiliary light is received by the AF sensor 16 as AF data (distance information) and transmitted to the system controller 13. From the system controller 13, the strobe 1
A light emission command signal for causing the light emitting element 5 to emit light is supplied to the light emitting circuit 14. In response to the light emission command signal, the main capacitor C incorporated in the light emission circuit 14 discharges and the strobe 15 emits light. As the light emission, two types of light emission, pre-light emission for photometry and light emission during actual shooting, are performed. The video signal from the CDS unit 3 is controlled by a gain control (G) in which the gain is controlled by a gain control signal from the system controller 13.
C) After the level is adjusted by the unit 11, the level detection unit 12
Sent to The level detection unit 12 performs known processing such as integration and peak detection processing for each divided area on the input video signal, and supplies it to the system controller 13 as photometric information Y output from the imager.

The system controller 13 performs pre-emission and photometry operation processes based on the distance information and photometry information received in this way, through processes described below in detail. That is, in this embodiment, the photometry operation is performed by the pre-flash of the multi-flash emission, and the strobe emission time is tabulated in advance based on the distance information and the photometry result and the charging voltage of the main capacitor built in the light emitting circuit 14. The calculation is performed by referring to a table (memory) or using a set function. According to the calculation, the memory for the table is not required, and the memory capacity can be saved. Thereafter, the shutter is operated for photographing.

If the light emission for photometry is performed many times, the exposure level converges to an appropriate exposure level. However, since the capacity of the main capacitor is limited, if the light emission for photometry is not reduced as much as possible, the strobe light emission during actual photographing is performed. The required electric power cannot be obtained, and missed photo opportunities will be missed. Therefore, at the time of the first light emission, pre-emission and photographing are performed by obtaining a relatively appropriate light emission amount by referring to the above table or calculating based on the distance information and the main capacitor charging voltage.

FIG. 2 shows a flowchart of the operation processing procedure in the above embodiment. Also, FIG.
Light emission time T (μsec) determined by the relationship between voltage and light emission amount
Are shown as dimming tables. Charging voltage, as shown in FIG. 4
As shown in the figure, the boundary codes A to B depend on the range of the boundary voltage value.
I, A-B, B-C, C-D, D-E, E-
F, F to G, and G to I are set. FIG. 5 shows light metering information Y and a light amount correction coefficient L ′ for correcting the amount of emitted light.
/ L is shown as a dimming correction table.
Here, L 'indicates an appropriate amount of light.

Referring to FIG. 2, first, the strobe is set to "O".
N "(step S1), and" O "
If not N ", normal shooting is performed (step S11),
If "ON", the distance information obtained from the AF sensor 16 is received (step S2), and the distance information and the necessary light emission amount are received.
The required light emission amount L is obtained with reference to a distance light control table indicating the relationship (step S3). Next, the main capacitor C
Is input (step S4), and based on the obtained charging voltage VC and the light emission amount L, a light emission time T is obtained with reference to FIGS. 4 and 3 (step S5). That is, the charging voltage VC, delimited code by referring to the table of FIG. 4, defining a light emission time T required from the resulting boundary code and the desired amount of emitted light L by referring to the dimmer table of FIG. 3 . Here, since the charging potential decreases every time light is emitted, the light emission time increases sequentially. Next, the imager photometric information Y based on the pre-flash emission of the strobe light is obtained from the level detector 12 under the conditions thus determined (step S6),
It is determined whether or not the level of the photometric information Y is within the exposure determination range (Step S7). Here, if not, Y → L ′ / L, L = L ′ with reference to the dimming correction table of FIG. 5 in order to obtain the correction amount of the light emission amount (step S).
8). For example, if the photometric information Y is 45, FIG. 5 shows that L '/ L is 2.00, indicating that twice the amount of emitted light is required. The charging voltage at this time is set to VC = VC ′ (step S9), and this charging voltage (boundary code)
The light emission time T is obtained based on the light emission amount L with reference to the light control table of FIG. 3 (step S10), and the process returns to step S6. On the other hand, in step S7, the photometric information Y
Is determined to be within the exposure determination range, the amount of emitted light is corrected through the same processing as in step S8 (step S12), and the charging voltage of the main capacitor C is input (VC = VC ') (step S13). 3 ), the light emission time T is obtained from the charging voltage VC and the light emission amount L with reference to the dimming table of FIG. 3 (step S14), and photographing and recording are performed (step S15).

Although the above embodiment has shown an example of application to an electronic still camera, the present invention is not limited to an electronic still camera, but uses an electronic imaging device such as a camera-integrated VTR or a normal silver halide film. It is needless to say that the present invention can be applied to a camera that has been used.

By the way, in the conventional photometric system, an external photometric sensor is used. Therefore, due to a shift in the optical positional relationship between the photometric sensor and the optical lens system, the center of the subject intended by the operator is not determined. Correct photometric data cannot be obtained. As a result, when the luminance difference near the center of the subject is large, the proper exposure is greatly deviated. Further, a special external photometric sensor must be provided, which has contributed to an increase in size and cost. On the other hand, according to the present invention, it is possible to obtain photometry based on appropriate data on the subject without deviation from the subject.

[0015]

As described above, the multi-flash light metering system according to the present invention obtains a relatively appropriate amount of emitted light based on distance information, and obtains the amount of emitted light and the charging voltage of the main capacitor. Since the pre-emission is performed by setting the emission time during the pre-emission, the discharge caused by the first pre-emission at the time of photometry of the main light-emitting capacitor is minimized, while reducing power consumption. In addition, it is possible to speed up convergence until necessary photometric information is obtained and an appropriate amount of emitted light is obtained. As a result, it is possible to avoid a shortage of light emission amount due to a decrease in the charging voltage of the main capacitor at the time of actual shooting, and it is possible to prevent a missed photo opportunity. In addition, if the imager photometry method is adopted in the present invention, photometry data for the same subject as in actual shooting can be obtained, so that not only the optimum exposure condition can be obtained but also the configuration is simplified and the cost is reduced. It is also effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a multi-flash light metering system according to the present invention.

FIG. 2 is a flowchart showing an operation processing procedure in the embodiment of FIG. 1;

FIG. 3 is a diagram showing a relationship between a light emission time T and a light emission amount and a charging voltage of a main capacitor in the embodiment of FIG.

FIG. 4 is a diagram showing a relationship between a main capacitor charging voltage value and a boundary code in the embodiment of FIG. 1;

FIG. 5 is a diagram showing a relationship between photometric information and a light quantity correction coefficient in the embodiment of FIG. 1;

[Explanation of symbols]

1 aperture 2 CCD 3 CDS section 4 AGC
Unit 5 imaging process unit 6 FM modulation unit 7 REC amplification unit 8 head 9 recording medium 10 CCD
Driving unit 11 GC unit 12 Level detection unit 13 System controller 14 Light emitting unit 15 Strobe 16 AF sensor 17 AF auxiliary light

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/222-5/257 G03B 15/05

Claims (2)

(57) [Claims] 1. An image using projection light from a flash light emitting means.
The photometric information suitable for image recording
Based on the output of the photometric means relating to the projected light by light emission
Got to getMulti-flash light metering systemSo
hand,Means for obtaining distance information to the subject; Means for determining the amount of emitted light based on the distance information; Detecting the charging voltage of the main capacitor of the flash light emitting means
Means, Based on the charging voltage and the amount of emitted light, the flash
Means for setting the light emission time at the time of pre-emission for the light means,  Multi-flash light metering characterized by comprising
system. 2. The multi-flash light metering system according to claim 1, wherein said light metering information is obtained by an imager metering method.