JP2002318412A - Flash light controller and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flash light controller capable of accurately metering the reflected light of preliminary light emission by appropriately setting the gain of a flash light metering part even when a photographic lens having a short focal distance is used or even when normal light is dark. SOLUTION: This flash light controller controls a flash light emitting part 15 performing the preliminary light emission before normal light emission, and is equipped with the flash light measuring part 13 measuring flash light reflected and returned from a subject at the preliminary light emission time, and a gain setting part 28 setting the gain of the flash light measuring part in accordance with the focal distance of the photographic lens 1. Then, the setting part 28 also sets the gain obtained when a subject luminance signal outputted from a normal light measuring part 9 is small higher than the gain obtained when the subject luminance signal is large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash control device and a camera for controlling the amount of flash light emission to an optimum amount.

[0002]

2. Description of the Related Art Heretofore, a so-called TTL light control method has been used as a control method for a flash light emitter of a single-lens reflex type digital camera or a silver halide camera. Among cameras that perform TTL light control, there is a camera that performs preliminary light emission before main light emission at the time of shooting, measures light reflected from a subject, and obtains information for main light emission. In such a camera, information such as the reflectance of the subject can be obtained by measuring and measuring the reflected light of the preliminary light emission before photographing, and the main light emission can be emitted with a more appropriate exposure.

In particular, in a digital camera in which a solid-state image sensor such as a CCD is placed at the position of a photographic film, it is difficult to perform TTL light control using the surface of the solid-state image sensor. In some cases, a necessary light emission amount is calculated, and the main light emission is performed with this light emission amount.

In such a camera, photometry of preliminary light emission is performed on a light flux diffused by a shutter curtain surface in a mirror-up state. There is one that calculates whether to emit light at the intensity. In some cases, the reflected light of the preliminary light emission is measured by a photometric element provided in the finder optical system in a mirror-down state, and the intensity of the main light emission is obtained by calculation to emit light.

[0005] JP-A-2000-187266 discloses that
There is disclosed a flash control device in which reflected light from a subject at the time of preliminary light emission is divided and photometrically measured, a reflectance distribution of the subject is obtained from the result, and information for main light emission is obtained. In the flash control device described in the above publication, the light emission amount required for the main light emission is also determined from the photometry result of the preliminary light emission, and the flash light emission unit performs the main light emission with the required light emission amount as a target. In such a method in which the light emission amount at the time of photographing is determined in advance based on the photometric output at the time of preliminary light emission, the light measurement accuracy at the time of preliminary light emission directly affects the light emission accuracy at the time of photographing. Photometric accuracy is very important.

[0006]

However, in such an apparatus as described above, the gain set in the flash photometry unit that measures the reflected light from the subject at the time of preliminary light emission (when the output is performed with respect to the incident light amount). If the setting of (amplification rate) is not appropriate, the signal generated by the reflected light of the preliminary light emission is too small, and thus the signal is out of the photometry range of the flash photometry unit, and the accuracy of the photometry value cannot be sufficiently obtained. . FIG. 6 is a diagram illustrating an example of the relationship between the amount of received light and the output in the flash photometer. In a region where the amount of received light is small, the output becomes unstable and the accuracy often decreases, as in diagrams A and B. In addition, when the output is small, the influence of noise or the like is liable to occur, and therefore, even in the processing after the output, the accuracy may be low in some cases.

[0007] As a specific example, for example, when the photographing distance is long, the amount of reflected light returning from the subject to the flash photometer during preliminary light emission is reduced. Therefore,
Japanese Patent Application Laid-Open No. 2000-338569 discloses a technique in which information on a shooting distance is detected by an encoder provided in a shooting lens, and the gain of the flash photometer is changed based on this information.

However, the photographing distance signal obtained by this method changes the accuracy and the upper and lower limits of the signal depending on the design of each interchangeable lens, and the difference in the focal length greatly affects the photographing distance signal. . A wide-angle lens with a short focal length has a greater depth of field than a lens with a long focal length,
Since the rotation angle of the distance ring is small, the accuracy of the shooting distance signal is low, and the longest shooting distance signal is short. That is, when the subject is far away, the distance ring rotation angle becomes smaller than the resolution of the encoder, so that the signal has poor accuracy and can output only a small value. Therefore, even if the gain of the flash photometer is adjusted by using this signal, especially when a wide lens is used, even if the subject is far away, the distance signal can be recognized only as close, so that an appropriate gain is set. There was a problem that the accuracy of the photometric value could not be obtained sufficiently because the setting could not be made.

Further, in a lens barrel having a short focal length, the angle of view is widened, so that the range which needs to be illuminated by flash light also becomes wide. In general, the illumination by the flash light emitting unit becomes darker toward the periphery, and the amount of light reflected back by the subject decreases. From this viewpoint as well, in a lens barrel having a short focal length, the signal generated by the reflected light of the preliminary light emission becomes small, out of the light meterable range of the flash light meter, and the accuracy of the light meter value cannot be sufficiently obtained. Often occurred.

On the other hand, the light measured by the flash photometer during the preliminary flash includes ambient light (hereinafter, “stationary light”) other than the flash, so that the gain set in the flash photometer depends on the influence of the steady light. Receive. Then, the above-mentioned JP-A-2000-33
No. 8569 discloses a technique for reducing the gain when the subject brightness is high (when the ambient light is bright). However, in the conventional flash control device, when the steady light is very dark, the amount of light reaching the flash photometry unit is small, out of the photometry range of the flash photometry unit, and the accuracy of the photometry value cannot be sufficiently obtained. There was a problem.

An object of the present invention is to appropriately set the gain of the flash photometer even when a photographing lens having a short focal length is used or when the stationary light is dark, to accurately adjust the reflected light of the preliminary light emission. An object of the present invention is to provide a flash control device capable of measuring light well.

[0012]

The present invention solves the above-mentioned problems by the following means. In addition, in order to make it easy to understand, description is given with reference numerals corresponding to the embodiment of the present invention, but the present invention is not limited to this. That is, the first aspect of the present invention is a flash control device for controlling a flash light emitting section (15) that performs preliminary light emission before main light emission,
A flash measuring unit (13) for measuring the flash reflected and returned by the subject during the preliminary light emission, and a gain setting unit (28) for setting the gain of the flash measuring unit according to the focal length of the taking lens (1). And a flash control device.

According to a second aspect of the present invention, in the flash control device according to the first aspect, the gain setting section (28) sets the gain when the focal length is short to be greater than the gain when the focal length is long. A flash control device.

According to a third aspect of the present invention, there is provided a flash control device for controlling a flash light emitting section (15) which performs a preliminary light emission before a main light emission, and measures a flash light reflected by an object and returned at the time of the preliminary light emission. A flash measuring unit (13), a stationary light measuring unit (9) for measuring stationary light, and a gain setting unit (28) for setting a gain of the flash measuring unit according to a subject luminance signal measured by the stationary light measuring unit. ).

According to a fourth aspect of the present invention, in the flash control device according to the third aspect, the gain setting section (28) sets a gain when the subject luminance signal is small and a gain when the subject luminance signal is large. A flash control device.

According to a fifth aspect of the present invention, there is provided the first to fourth aspects.
A camera comprising the flash control device according to any one of the above, wherein the flash device having the light emitting section (15) is detachable.

[0017]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG.
FIG. 1 is a diagram showing an optical system of a flash control device for a camera according to the present invention. The camera shown in FIG. 1 is a so-called digital still camera in which a flash light emitting device having a flash light emitting unit 15 is detachable from a camera body, and converts an image formed on an image sensor 14 into an electric signal and records it. It is. The light beam that has passed through the taking lens 1
To form an image on the diffusion screen 3 once. Thereafter, the light reaches the photographer's eye through the condenser lens 4, the pentaprism 5, and the eyepiece 6.
On the other hand, a part of the light beam diffused by the diffusion screen 3 is re-imaged on the stationary light metering section 9 through the condenser lens 4, the pentaprism 5, the light measuring prism 7, and the light measuring lens 8. The stationary light metering unit 9 uses a light receiving element such as an SPD (silicon photodiode), for example, and divides the object field into five areas B1 to B5 as shown in FIG. It has a structure that can output each photometric value.

At the time of photographing, the aperture 10 is stopped down to a predetermined value, and at the same time, the quick return mirror 2 is flipped up. Thereafter, at the time of preliminary light emission by the flash light emitting unit 15,
A part of the light flux substantially formed and reflected on the shutter 11 is re-formed on the flash photometer 13 through the dimming lens 12. At the time of the main light emission by the flash light emitting unit 15, the shutter 11 is opened, and the light flux is imaged on the light receiving surface of the image sensor 14 constituted by, for example, a CCD.

The flash photometer 13 comprises an SPD, a capacitor for accumulating the photocurrent from the SPD, an amplifier, and the like. As shown in FIG. The areas S1 to S5 correspond to B1 to B5 in FIG. 3, respectively. The flash photometer 13 multiplies the photocurrent generated by the SPD by a different amplifier gain for each area, and accumulates the amplified current in the integrating capacitor. At the time of reading, the charge stored in the capacitor corresponding to each area is read out as a voltage value, and is converted into digital data by the A / D converter built in the microcomputer 100 (see FIG. 2) on the camera body side. It is captured.

The quick return mirror 2 is a half mirror that transmits a part of the light. A part of the transmitted light is bent downward by the sub-mirror 16 in FIG. Focus detector 17
Detects the focus state of any one of the central regions F1 to F5 of the object scene shown in FIG. 3, and drives the photographing lens 1 until the in-focus state is achieved.

FIG. 2 is a block diagram showing a signal flow of the flash control device according to the present embodiment. When performing focus adjustment, the focus state is detected by the focus detection unit 17, and the lens optical system 26 is driven by the motor of the lens drive unit 24. The lens barrel is provided with an encoder 33 that outputs a signal corresponding to the rotation angle of the distance ring, which corresponds to the extension amount. When the lens barrel is in focus, a signal obtained from the rotation angle of the distance ring in that state is output as a signal corresponding to the distance to the subject. This signal is processed by the microcomputer 25 on the lens side to obtain a shooting distance signal. This photographing distance signal is transmitted to the flash control device (microcomputer) 100 on the camera body side through an electrical contact between the camera body and the lens barrel. Various calculations and controls are performed in the microcomputer 100 on the camera body side.

As shown in FIG. 3, the stationary light meter 9
This is a circuit that divides the object field into five and measures the constant light. The exposure calculator 22 calculates the output from the stationary light meter 9 and the open F value, focal length, and exit pupil position of the taking lens stored in the lens microcomputer 25 which is a microprocessor provided in the lens barrel. Based on the lens information and the sensitivity information of the image sensor 14 from the sensitivity setting unit 29, an appropriate exposure value for the steady light exposure is calculated, and it is decomposed into an aperture value and a shutter value and sent to the sequence control unit 20 and the like. Output.

When a release signal is input from the release switch 27, the sequence control unit 20 flips up the quick return mirror 2 and stops down the aperture 10.
A command for preliminary light emission is issued to the flash light emitting unit 15 and thereafter, the shutter 11 is controlled, and at the same time, a series of operations such as issuing an instruction for main light emission to the flash light emitting unit 15 again are controlled.

FIG. 5 is a diagram schematically showing a sequence of preliminary light emission and main light emission. The sequence control unit 20 receives signals from the exposure calculation unit 22, the sensitivity setting unit 29, etc.
It controls the flash light meter 13, flash light emitter 15, and the like. The sequence control unit 20 controls the gain setting unit 2 immediately before the preliminary light emission.
8 sets the amplifier / gain of the flash photometric unit (gain setting 1 in FIG. 5), and then performs preliminary light emission in which the flash light emitting unit 15 emits light with a predetermined small guide number at least once (hereinafter, chop light emission). Let it do. Then, the flash light emitting unit 15 continues to perform the chop light emission until a stop signal indicating that the amount of light received by the flash photometric unit 13 has reached the predetermined value or the number of times of the chop light emission has reached the predetermined value.

While the chop light emission is continued, the flash light meter 13 measures the light reflected from the subject in the preliminary light emission, and accumulates the generated photocurrent (preliminary light emission integration in FIG. 5). The microcomputer 100 reads the output of the flash photometer 13 (read 1 in FIG. 5) and
A / D conversion is performed from the D port and taken in as data. Thereafter, the same gain as that during chop light emission is set (gain setting 2 in FIG. 5), photometry is performed by the flash photometric unit 13 without flash light emission for the same accumulation time, and the steady light is accumulated. (Steady light integration in FIG. 5). This is because the accumulated value of the photocurrent during the preliminary light emission includes not only the photocurrent due to the flash light but also the photocurrent due to the stationary light. This is for obtaining the net (preliminary flash emission component) preliminary light emission accumulation value. Based on this net preliminary light emission accumulated value and the sensitivity of an image pickup device such as a CCD or a film, etc., it is calculated how many times the preliminary light emission should be performed during photographing and transmitted to the flash light emitting unit 15 (FIG. 5). (The main light emission amount calculation / communication in the above) to perform the main light emission. In the main light emission, the flash light emitting unit 15 emits a flash with the instructed light amount.

The gain setting section 28 is a section for calculating the amplifier gain of the flash photometry section 13 and setting the gain of the flash photometry section 13. The flash photometer 13 multiplies the photocurrent generated by the SPD by a different amplifier / gain for each area,
The amplified current is stored in the integrating capacitor. At the time of reading, the charge stored in the capacitor corresponding to each area (see FIG. 4) is read as a voltage value. As described above, if the gain is an inappropriate value, the reflected light of the flash cannot be measured with high accuracy. Therefore, it is extremely important to appropriately set the gain. The gain setting is
It is desirable that the output obtained by multiplying the expected amount of reflected light of the preliminary light emission by a gain does not cause overflow or underflow. To this end, the gain is adjusted using some information at the time of shooting.

This calculation is performed by the microcomputer 10 on the camera body side.
Performed at 0. Specifically, the following gain is adjusted. (1) When the aperture value is a small aperture, it is expected that the reflected light entering the flash photometric element is small, so the gain is increased. (2) Even when the guide number per one chop light emission of the preliminary light emission is small, the gain is increased accordingly. (3) When the luminance of the stationary light is high, the output of the flash photometric element is expected to saturate quickly, so the gain is reduced. (4) At the time of bounce shooting, the gain is increased because reflected light is expected to be small. (5) When the distance to the subject is long, the gain is high because the reflected light is expected to be small, and when the distance is short, the gain is low because the reflected light is expected to be large. (6) Obtain focal length information from the lens microcomputer 25,
If the focal length is shorter than a certain value, the gain of the flash photometer is increased. (7) When the subject brightness due to the stationary light is small, the gain of the flash photometry unit is increased. The methods (1) to (5) are
JP-A-2000-338569 and JP-A-2001-
Since the method is performed by Japanese Patent Application Laid-Open No. 91989 or the like, description thereof will be omitted, and the methods (6) and (7) will be described below.

Method (6) As described above, conventionally, an image pickup distance signal obtained by detecting a distance ring rotation angle of a lens barrel by an encoder is used,
The gain of the flash photometer 13 was adjusted. However, in this case, when the wide lens is used, even if the subject is far away, the distance signal can be recognized only as near, so that a sufficient gain may not be obtained.
Therefore, in the present embodiment, the focal length information is obtained from the lens microcomputer 25 on the lens barrel side, and when the focal length is shorter than a certain value, the gain of the flash photometer is increased by a certain value.

Here, as a method of increasing the gain, the following method can be adopted. A: It is determined whether or not the focal length is smaller than a predetermined fixed value, and if true (if the focal length is small), an operation such as increasing the gain by a certain value is performed (used in the present embodiment). . B: The shorter the focal length, the higher the gain. Such a calculation may be performed by the microcomputer on the camera body side to obtain the gain. In the case of a zoom lens or the like whose focal length can be changed, a signal corresponding to the zoom position (focal length) set at the time of photographing is obtained from the lens microcomputer 25. As described above, the focal length information is obtained from the lens microcomputer, and when the focal length is shorter than a certain value, the gain of the flash photometric unit 13 is increased by increasing the gain of the flash photometric unit. And reflected light can be accurately measured.

Method (7) As described above, the photocurrent accumulation value during the preliminary light emission includes the photocurrent accumulation value due to the stationary light. Of course, when the subject luminance obtained by the steady light meter 9 is large, the contribution of the photocurrent accumulation value due to the steady light also becomes large. On the contrary,
When the brightness of the subject is small, the contribution of the photocurrent accumulation value due to the stationary light can hardly be expected, so that the entire photocurrent accumulation value is expected to be relatively small. Accumulated value,
That is, when the output of the flash photometer becomes extremely small, the linearity (linearity) of the output value with respect to the input value deteriorates,
Accuracy may be reduced. Therefore, when the subject luminance due to the steady light is small, the accuracy of the flash photometry can be prevented from being deteriorated by increasing the gain of the flash photometry unit. Also in the case of this method, the gain may be increased by a certain value when the subject luminance obtained by the stationary light meter 9 is smaller than a predetermined value, or the gain may be increased as the subject luminance decreases. You may. In the present embodiment, the gain is increased by a certain value when the subject brightness obtained by the stationary light meter 9 is smaller than a predetermined value.

(Modifications) Various modifications and changes are possible without being limited to the above-described embodiments, and these are also within the equivalent scope of the present invention. For example, in the present embodiment, an electronic still camera using an image sensor such as a CCD has been described as an example, but the present invention can be similarly applied to a camera that exposes a silver halide film.

[0032]

As described above in detail, according to the present invention, the gain setting unit for setting the gain of the flash measurement unit according to the focal length of the taking lens and / or the subject luminance signal measured by the steady light measurement unit. Is provided, the gain to be set in the flash photometer can be appropriately determined, and the reflected light of the flash at the time of the preliminary flash can be measured without deteriorating the accuracy. Therefore, it is possible to accurately measure the reflected light of the preliminary light emission, and perform the main light emission using the result, thereby performing flash photography at an appropriate exposure level.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system of a flash control device for a camera according to the present invention.

FIG. 2 is a block diagram showing a signal flow of a flash control device according to the embodiment.

FIG. 3 is a diagram illustrating a divided shape of a stationary light metering unit 9 and a focus detection unit.

FIG. 4 is a diagram showing an optical system of a flash photometer 13 and a divided shape of a photometry area.

FIG. 5 is a diagram schematically illustrating a sequence of preliminary light emission and main light emission.

FIG. 6 is a diagram illustrating an example of the relationship between the amount of received light and the output in a flash photometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Quick return mirror 3 Diffusion screen 4 Condenser lens 5 Pentaprism 6 Eyepiece 7 Photometry prism 8 Photometry lens 9 Steady-state photometry unit 10 Aperture 11 Shutter 12 Dimming lens 13 Flash photometry unit 14 Image sensor 15 Flash Light emitting unit 16 Sub-mirror 17 Focus detecting unit 22 Exposure calculating unit 24 Lens driving unit 25 Lens microcomputer 26 Lens optical system 27 Release switch 28 Gain setting unit 29 Sensitivity setting unit 100 Microprocessor

Claims (5)

[Claims] 1. A flash control device for controlling a flash light emitting unit that performs a preliminary light emission before a main light emission, comprising: a flash light measuring unit that measures a flash light reflected back by a subject during the preliminary light emission; A flash control device comprising: a gain setting unit that sets a gain of the flash measurement unit according to a focal length. 2. The flash control device according to claim 1, wherein the gain setting unit sets a gain when the focal length is short to be higher than a gain when the focal length is long. Flash control device. 3. A flash control device for controlling a flash light emitting unit for performing preliminary light emission before main light emission, comprising: a flash light measuring unit for measuring a flash light reflected back by an object during the preliminary light emission; A flash control device comprising: a steady light measuring unit for measuring; and a gain setting unit for setting a gain of the flash measuring unit according to a subject luminance signal measured by the steady light measuring unit. 4. The flash control device according to claim 3, wherein the gain setting unit sets a gain when the subject luminance signal is small to be higher than a gain when the subject luminance signal is large. Flash control device. 5. The method according to claim 1, wherein:
A camera, comprising: the flash control device according to claim 1; and a flash device having the light emitting unit is detachable.