JP2003107566A - Camera with electronic flash unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic flash unit which operates in such a lighting mode that electronic flash light appears to be as non-glaring as possible and a camera with the electronic flash unit. SOLUTION: The camera with the electronic flash unit has a sensor which receives light from a subject for measuring the subject distance, a luminance measurement part (light receiving sensors 3a and 3b) which measures the brightness (luminance) in a photographing plane with the sensor output, and an electronic flash control part (CPU 1) which switches the lighting mode of auxiliary light in exposure according to the obtained subject distance. The CPU 1 selectively switches the camera between, for example, a lighting mode for obtaining a specific quantity of light by single-time lighting and a lighting mode for obtaining a specific quantity of light through multiple-time lighting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strobe device, and more particularly to a camera equipped with the strobe device.

[0002]

2. Description of the Related Art As a camera exposure aid, for example, a technique of "strobe emission" by a so-called strobe device, which causes a xenon (Xe) tube or the like to discharge and emit light, has been known for a long time. As a technique in this field in recent years, for example, Japanese Patent Publication No. 5-3
Japanese Patent No. 8938 proposes a "multi-flash strobe" that controls a plurality of strobe devices. Also, patent 3
No. 026513 and the like also propose a technique of reducing red-eye by emitting light a plurality of times even with a single-flash strobe device. With such a stroboscopic light emission technology, it is possible to shoot in a dark condition where the subject is placed.

[0003]

Generally, when a strong stroboscopic light is emitted in a dark condition requiring a stroboscopic light, a person or an animal as a subject to be photographed receives a very strong stimulation. I felt and felt uncomfortable. However, in the above-mentioned related art, the matters (for example, the feeling of use of the user) have not been fully considered. In addition, if the light emitted from the strobe device is too weak, it will be lost by the ambient light in a backlit scene or the like, and the subject image will become a blackened photograph, and the expected beautifully photographed photograph cannot be obtained in many cases.

The present invention was devised in light of the above problems by paying attention to these techniques from an early stage, and an object of the present invention is to stroboscopes operating in a light emitting mode in which stroboscopic light is not felt as bright as possible. An object is to provide a device and a camera with the strobe device.

[0005]

[Means for Solving the Problems] In order to solve the above problems and achieve the object, the present invention takes the following means. That is, according to the first aspect, a sensor that receives light from the subject to measure the subject distance, a brightness measuring unit that measures the brightness in the screen based on the output of the sensor, and the subject distance and the brightness. According to the above, there is proposed a camera with a strobe device including a strobe control means for switching the emission mode of auxiliary light at the time of exposure.

The strobe control means is a camera that switches between a first light emission mode in which a predetermined light amount is obtained by one light emission and a second light emission mode in which a predetermined light amount is obtained by a plurality of light emissions. Further, there is proposed a camera characterized in that the strobe control means selects the second light emission mode when the subject distance is short and the brightness in the screen is a predetermined darkness. The sensor is divided into a plurality of light receiving portions for detecting the image signal of the subject. In addition, a camera is proposed in which this sensor has a light receiving surface for receiving the reflected signal light of the signal light projected on the subject.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Usually, if the strobe device emits a small amount of light and emits a small amount of light, the glare felt by the subject's eyes can be suppressed, but a device for solving the problem that sufficient exposure cannot be obtained can be solved. The present invention is realized by the following embodiments. One of the basic ideas of the flash device according to the present invention is that the camera obtains a predetermined amount of light by repeatedly emitting a small amount of light to a nearby subject, and an appropriate amount of exposure can be expected for shooting. It is something to do.

However, in the case of repeated light emission as described above, a long exposure time is required. It is necessary to avoid the problem that light (external light) from other than the main subject enters during the exposure time and is overexposed, which deteriorates the quality of the photograph.

Therefore, in the camera with a strobe device according to the present invention, in order to avoid the occurrence of such a problem particularly in such a photographing scene, for example, for a distant object, 1 is set.
The light emission mode is appropriately controlled so as to switch to a large light amount light emission operation in which “one shot” light emission is performed so that sufficient exposure can be obtained by one light emission.

An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows the configuration of an autofocus camera (AF camera) according to this embodiment. This AF camera is configured such that a strobe device is built in the camera body or can be attached to the outside as needed.

Further, this AF camera is configured to include a photometric device for exposure detection and a distance measuring device for AF inside. That is, the release S related to the start of distance measurement and photometry
Each component is controllably connected as shown in the drawing by an arithmetic control circuit (CPU1) which is composed of, for example, a one-chip microcomputer to which a switch 5 such as W is connected. The CPU 1 has a check unit 1 having a predetermined check function (details will be described later).
a and the RAM 6 are provided adjacent to each other.

This AF camera has a lens driver (LD).
7 and a photographing lens 8 driven by the camera 7, a pair of light receiving lenses 2a and 2b and sensor arrays 3a and 3b, and a CPU 1 via an A / D converter 4.
It is connected to the. Further, as will be described later in detail, a strobe device is connected by the CPU 1 so as to be driven in a predetermined light emission form.

The AF camera constructed as described above uses the two light-receiving lenses 2a and 2b in order to correctly focus the photographing lens 8 on the subject 100.
This is a distance measuring camera in which an image of 0 is guided to the sensor arrays 3a and 3b, and the parallax B of the light receiving lenses 2a and 2b is used to calculate the distance L based on the "principle of triangulation." Therefore, the output of each pixel of the sensor array is A / D
It is input to the CPU 1 via the conversion unit 4. At this time, data that is not suitable for distance measurement is checked by passing through the check unit 1a and is restricted from being stored in the RAM 6, or even if temporarily stored in this RAM 6, it is cleared and the memory space is enabled. Is available for use.

The magnitude of the output data from each pixel of the sensor arrays 3a and 3b is stored in the RAM 6 in the CPU 1 as the magnitude of the digital value. From the magnitude result, the CPU 1 determines the subject image by the parallax B of the light receiving lenses 2a and 2b. When it is determined that the object is present at a position displaced by the relative position x, the subject distance L is calculated by the calculation based on the following equation. L = B · f / x (formula) where f is the focal length of the light receiving lenses 2a and 2b.

Further, a switch 5 (not shown) capable of detecting a release operation of a photographer is connected to the CPU 1, and the operated state of the switch 5 (for example, in the case of a two-step switch, a first-step release operation). The above-described distance measuring device is operated to calculate the subject distance L, and according to the resulting subject distance L, the photographic lens 8 is focused through the lens driver (LD) 7 until zooming is achieved. Drive. In this example,
The light emitting tube 9 of the strobe device is controlled to emit light as an aid of exposure according to the shooting conditions.
It may be used as an auxiliary light for.

In the AF camera configured as described above, the strobe device and its light emission control when the present invention is applied will be described in detail. FIGS. 2A to 2D show examples of shooting scenes, respectively, and specifically show a case of using a strobe device.

First, the scene of FIG. 2 (a) is a situation in which strong light from the strobe device is most desired to be prevented. If you want to take a big picture of your baby's face indoors, you often need a flash to compensate for the lack of exposure. However, at that time, since the baby's eyes are accustomed to the brightness of the room, there is a risk that the baby will start crying when suddenly irradiated with a bright strobe light. Under such circumstances, the AF camera according to the present embodiment is designed to weakly adjust the strobe light and increase the number of times the light is emitted to control the exposure so that the exposure is reasonably compensated.

In addition, even when photographing the same baby,
As shown in FIG. 2 (b), in the outdoor backlight scene, the baby's eyes are sufficiently accustomed to the outdoor brightness, so even if the strobe light is a little strong, it does not cause much stimulation.
It's not enough to cry. However, in such a case, if the light is emitted multiple times, the exposure time during which the shutter is open becomes long, and the ambient light (external light) wraps around during that period, so the exposure proceeds too far and the background becomes white. The usual side effect is that In addition, there is energy loss that occurs when the current of the Xe tube is turned on / off to stop the strobe emission, and one emission is advantageous because a larger amount of light can be taken out.
When the shutter is opened as in the timing illustrated in (a), it is preferable to supply a current to the Xe tube for a time of t _st to obtain a large amount of light.

Alternatively, in a flower macro photography scene as shown in FIG. 2C, even if the distance to the flower of the subject is short, the light from the background is the main subject before the sufficient strobe light is supplied if the background is bright. Since the flower wraps around and the flower as shown in FIG. 2 (d) is crushed in black, resulting in a failure photograph (exposure failure), multiple flashes are not preferable in close-up photography in this case.

In order to discriminate these photographing scenes based on such an idea, a method of accurately discriminating whether or not it is a backlight scene on the basis of the output of the distance measuring sensor array is used in the present embodiment. It is adopted. That is, FIG.
In each of the shooting scenes (a), (b) and (c), for example, the sensor output (image signal) obtained from the sensor array 3a is
By photometry, it is possible to obtain a waveform pattern representing the luminance distribution as shown in FIGS. 3 (a), 3 (b) and 3 (c), respectively.

As shown in FIG. 3A, the sensor output difference between the central photometric portion C of the main subject existing in the vicinity of the central portion of the screen and the peripheral left photometric portion L or right photometric portion R becomes large during backlighting. . Therefore, as shown in FIGS. 3B and 3C, by determining the output difference ΔBV of these sensor data and determining the degree thereof, it is determined whether or not the shooting scene is in the backlit state. Yes (details described below).

Then, based on the result of the determination as described above, by appropriately selecting and controlling from a plurality of light emission modes (described later in detail) provided for strobe light emission, it is most suitable for the situation of the shooting scene. It is possible to obtain auxiliary light. As a result, the electronic camera is equipped with a user-friendly strobe device with minimal glare, and a photograph of a beautiful subject image can always be obtained.

The above-mentioned strobe device and its light emission form will be described in more detail. FIG. 4 shows the configuration of this strobe device. This strobe device has Xe
It has an arc tube 9 such as a tube, a trigger circuit 22 and a pulse circuit 23 forming an emission drive system 9a for driving the same to emit light, an IGBT 20 as a trigger, and a main capacitor 21 as a power supply source. Main capacitor 2
When the electric charge of 300 Vt stored in 1 flows, light emission occurs in the Xe tube of the arc tube 9. For this light emission, a higher voltage is generated by the trigger circuit 22 of the arc tube 9 of the strobe device.
Is applied to the gas inside the Xe tube, causing the current to start flowing.

If the IGBT 20 is on, light emission continues until the charge in the main capacitor 21 is exhausted, and the pulse circuit 23 turns on / off the gate of the IGBT 20.
If FF is repeated, it can be controlled to emit a large number of times. Further, the CPU 1 has a strobe control means for controlling the stroboscopic light emission so that it can operate as a part of a predetermined control program.

The one-time light emission and the multiple-time light emission by the strobe device, which is one of the features of the present invention, is shown in FIG.
The light emission control such as the pattern 1 shown in (a) and the pattern 2 shown in FIG. 5 (b) is performed in cooperation with the trigger circuit 22 and the pulse circuit 23 in accordance with a command from the CPU 1, so that an appropriate light emission form is obtained. Controlled. Each of these circuits is controlled based on a control program, which will be described later and runs on the CPU 1. On the other hand, when the light is emitted a large number of times, as shown in the pattern 2 of FIG. 5B, it is necessary to keep the shutter open during that time, which causes the above-described problem at the time of backlighting.

FIG. 6 is a flow chart showing the control procedure of the AF camera of this embodiment. This is a part of the control flow of the photographing control program operating in the CPU 1, and each unit is controlled as follows.
In step S1, the distance measuring device first measures and calculates the subject distance L (S1). In step S2, the photometric device measures the brightness of the screen. Here, it is assumed that average brightness is detected from the output of the sensor array for distance measurement (S2). In step S3, the brightness distribution is determined based on each sensor output of the sensor array as described in FIG. 3 (S3).

[0027] Then, in step S4, based on the FN _o photometric brightness information obtained by the B _v and film sensitivity and the imaging lens of the step S2, it is determined whether or not the flash light emission is required during exposure (S4 ). If unnecessary, the process branches to step S11 to focus on the distance of the value L obtained in step S1 (S11). After that, exposure control (S12) is performed without strobe light emission, and a series of photographing processing is ended. On the other hand, when the film sensitivity is lower than a predetermined value or when FN _o is added (considered) and the screen brightness is insufficient and the screen is dark and stroboscopic light emission is required, the process proceeds to the next step S5.

[0028] In steps S5 S6, following the L <L _o of determining whether (S5), the subject is determined whether or not the state of the backlight (S6). In a normal strobe device, if the irradiation target is far, the amount of light does not reach a large amount due to energy loss at the time of light emission ON / OFF as described above, and the strobe light does not reach a long distance. Therefore, the above step S6 is NO only under the condition that the distance is shorter than the predetermined distance L _o and there is no backlight.
It is determined that it is similar to the baby shooting scene illustrated in FIG. 2A, and the subsequent step S7
After focusing on the subject distance L (S7), FIG.
The exposure is performed with strobe assistance by multiple flashes as in the pattern 2 illustrated in FIG.

However, if the condition is not satisfied, the condition shown in FIG.
After determining that the scene is as shown in (b) or FIG. 2 (c) and branching to step S9, the processing is further performed as follows. That is, in the case of a backlit scene at a long distance as shown in FIG. 2B and in the case of a backlit scene at a short distance as shown in FIG. 2C, each distance L is focused (S9), and step In step S10, exposure photography is performed by flash control of one emission such as pattern 1 illustrated in FIG. 5A (step S1).
0). Then, this photographing process is ended.

As described above, according to the present embodiment, it is possible to provide a camera that realizes exposure control by a large number of flashes, does not cause the subject's face to be crushed in black, and is capable of stroboscopic photography in which the subject does not feel glare. . In addition, it is effective for multiple subjects such as babies to use multiple flashes with less glare, and automatically determines that the shooting scene has no side effects. , It is possible to take a photograph without any stimulus to the eyes of the subject.

(Modification) The above-described embodiment may be modified as follows, and the present invention can be applied. Figure 7
~ A modification thereof will be described in detail with reference to each drawing of Fig. 9. For example, an AF camera having a configuration shown in a block circuit diagram in FIG. 7 is also an AF camera using an active type AF device here, and has a simple configuration using inexpensive components as compared with an active type AF using a sensor array. Can be provided.

That is, each component is controllably connected as shown by the CPU 1 to which a switch 5 such as a release switch for starting distance measurement and photometry is connected. For example, the photometric system includes a photometric sensor 30, a photometric circuit 31, and a photometric lens 32, and the light projecting system includes a light projecting lens 33, an infrared light emitting diode (IRED) 34, and a light emitting circuit 35. As a light receiving system, a light receiving lens 36
And a light position detecting element (PSD) 37,
The distance calculation circuit 38, the stationary light removal circuit 39, and the stationary light amount detection circuit 40 are connected as shown. Further, the arc tube 9 of the strobe device is controllably connected to the light emission control section 9a.

In the AF camera having such a structure,
When current is supplied to the infrared light emitting diode (IRED) 34 by the light emitting circuit 35 to emit light, the distance measuring light is projected onto the subject 100 via the light projecting lens 33. The reflected signal light is transmitted through the light receiving lens 36 to a light position detecting element (PSD).
It is incident on 37. The position of the incident light changes depending on the subject distance L based on the principle of triangulation.

PSD 37 for converting the position of light into a current signal
Since light other than the distance measuring light is also incident on, the distance measuring light is pulsed light. The photocurrent due to the stationary light is removed by the stationary light removing circuit 39, and only the photocurrent due to the pulsed signal light component separated by this circuit acting as a filter is input to the distance calculating circuit 38. The subject distance L can be detected. At this time, the removed stationary photoelectric flow rate is input to the CPU 1 via the stationary light amount detection circuit 40 and is subjected to the determination process.

Since the PSD 37 monitors only a part of the subject, the stationary light quantity is an output corresponding to spot metering. Therefore, if the photometric lens 32 for average photometry and the photometric sensor 30 are respectively provided, the photometric circuit 31
Through the, the CPU 1 can make a judgment based on the results of the average photometry and the spot photometry to judge whether the scene to be photographed is a backlight.

FIG. 8 is a flowchart showing the "backlight determination" routine in the flash control of this modification. Follow the procedure below to perform backlight determination. First, from step S20, the stationary light amount incident on the PSD 37 is determined (S2
0), the brightness BV ₁ is calculated in order to measure the display state when the subject is present from this steady light amount (S21).

In step S22, the photometric sensor
Average photometric value BV based on the output of 30 ₂Is calculated (S2
2). Then, in step S23, the result of the above calculation
Obtained brightness BV₁And average photometric value BV₂Compare using
The following cases are classified based on the magnitude relationship. This and
BV₁+ BV₃<BV₂ Is used as a comparison expression (S2
3). If the predetermined difference BV₃If there is more difference than
Returns to step S24 and determines that the subject is backlit.
(S24).

As described above, according to this modification, even with a camera equipped with an active type autofocus function that can be provided with a simpler structure, for example, a shooting scene as shown in FIG. It is possible to automatically perform flash photography that is easy on the eyes.

(Other Modifications) The following modifications may be made. FIG. 9 shows another modification.
This is an example in which light is emitted a large number of times while changing the strobe emission interval, and illumination is performed with a light emission pattern that gradually adjusts to the intensity of strobe light so that glare is less likely to occur. That is, as shown by the light emission cycle of the timing chart, there is a device for light emission control that gradually increases the light emission time for one light emission when the light is emitted multiple times, and gradually adjusts the subject's eyes to the light. It can also be easily implemented.

By carrying out such a modification, it becomes possible to perform stroboscopic photography with less stimulus to the subject. Besides this, various modifications can be made without departing from the scope of the present invention.

Although the description has been given based on the embodiment, the following invention is included in this specification. (1) In an AF camera with a strobe device that measures the distance to a subject by an active method, a light receiving sensor that senses light from the subject, and a luminance measurement that measures the subject luminance in the shooting screen based on the output of this light receiving sensor AF having a strobe device, which has a means and a strobe control means for judging a shooting scene based on the obtained distance and brightness and selectively switching a light emission mode of auxiliary light at the time of exposure.
Can provide a camera.

(2) The strobe control means uses a first light emission form that obtains a predetermined light amount or more by one light emission and a second light emission form that obtains a predetermined light amount by a plurality of light emission in the shooting scene. It is possible to provide the AF camera described in (1), which is switched accordingly. (3) When the subject is at a short distance, the light emission mode is switched so that the light is illuminated many times, and when the subject is at a long distance, the light emission mode is switched to one emission.
An F camera can be provided.

(4) Illuminates with a large number of flashes during wide-angle shooting (Wide), and illuminates with a single flash during telephoto shooting (Tele) (1)
The AF camera described in 1. can be provided. (5) If the ISO sensitivity of the film used for shooting is higher than the specified value, it is illuminated with multiple flashes, and if the ISO sensitivity of the film is lower than the specified value, it is illuminated with one shot. The AF camera described can be provided.

[0044]

As described above, according to the present invention, it is possible to provide a strobe device that operates in a light emitting mode in which strobe light is not felt as bright as possible, and a camera equipped with the strobe device.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a configuration of a main part of an autofocus camera according to an embodiment of the present invention.

2A to 2D show an example of a shooting scene in the present embodiment, FIG. 2A is an explanatory view of an indoor close-up shooting scene, and FIG. 2B is a backlit shooting scene in the field. Illustration,
(C), (d) is explanatory drawing of the close-up photography scene by backlight.

3A to 3C show photometry results (luminance distribution) by a sensor array in this camera, and FIG.
Is a graph showing the sensor output waveforms of the center of the main subject and the left and right photometric parts, and (b) and (c) are graphs showing the output difference of the sensor data for backlight determination.

FIG. 4 is a circuit diagram showing a circuit for controlling strobe light emission.

5 (a) and 5 (b) show a light emission form in a strobe device by a pulse, a trigger, and opening / closing of a shutter,
(A) is a timing chart showing a pattern of one-time light emission, and (b) is a timing chart showing a pattern of multiple-time light emission.

FIG. 6 is a flowchart showing strobe control according to the present embodiment.

FIG. 7 is a block circuit diagram showing an active type autofocus camera as a modified example of the invention.

FIG. 8 is a flowchart showing a backlight decision of strobe control as a modified example.

FIG. 9 is a timing chart showing a pattern for changing the stroboscopic light emission interval as a modified example.

[Explanation of symbols]

1 ... Arithmetic control circuit (CPU: various control means), 1a ... Check section 2a, 2b ... Receiving lens, 3a, 3b ... Sensor array (luminance measuring means), 4 ... A / D converter, 5 ... switch (release SW), 6 ... RAM, 7 ... Lens driver (LD), 8 ... Shooting lens, 9 ... Arc tube (Xe tube), 20 ... IGBT (trigger), 21 ... Main capacitor, 22 ... Trigger circuit, 23 ... pulse circuit, 30 ... Photometric sensor, 31 ... Photometric circuit, 32 ... Photometric lens, 33 ... Projector lens, 34 ... Infrared light emitting diode (IRED), 35 ... Light emitting circuit, 36 ... Light receiving lens, 37 ... Optical position detector (PSD), 38 ... Distance calculation circuit, 39 ... Stationary light removal circuit, 40 ... Stationary light amount detection circuit. S1 to S12 ... Shooting processing procedure (camera sequence), S20 to S24 ... Backlight determination procedure.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03B 13/36 G03B 3/00 AF term (reference) 2H002 AB04 AB06 CD06 CD07 CD11 CD12 DB25 GA31 2H011 AA01 BA14 DA07 2H051 AA01 BB16 EB03 EB07 2H053 AB03 AD06 AD12 AD21 AD23 BA33 DA08

Claims (5)

[Claims] 1. A sensor for receiving light from a subject for measuring a subject distance, a brightness measuring unit for measuring brightness in a screen by the sensor output, and an exposure time according to the subject distance and the brightness. 2. A camera with a strobe device, comprising: a strobe control unit that switches the emission mode of the auxiliary light. 2. The strobe control means switches between a first light emission form for obtaining a predetermined light amount by one light emission and a second light emission form for obtaining a predetermined light amount by a plurality of light emission. The camera according to claim 1. 3. The strobe control means selects the second light emission mode when the subject distance is short and the brightness in the screen is a predetermined darkness. The camera described in 2. 4. The camera according to claim 1, wherein the sensor is divided into a plurality of light receiving portions for detecting an image signal of the subject. 5. The camera according to claim 1, wherein the sensor has a light receiving surface for receiving the reflected signal light of the signal light projected on the subject.